Advances in Composite Laminate Theories

Advances in Composite Laminate Theories This paper reviews the Composite Laminate Theories that have already been proposed and developed in the recent years. These theories mainly focus on the macro mechanical analysis of the composite laminates which provides the elastic relations of the lamina. Stress-induced failure can occur in multiple ways in composite materials. Hence to understand and predict transverse shear and normal stress accurately, various composite laminate theories have been developed. The advantages and disadvantages of each model are discussed in detail. In this study, the Composite Laminate Theories are divided into two parts: (1) Single Layer Theory, where the entire plate is considered as one layer and (2) Layer Wise Theory, where each layer is treated separately for the analysis. It starts with displacement-based theories from very basic models such as Classical laminate theory to more complex higher-order shear deformation theory. [6] INTRODUCTION The requirement of composite materials has grown rapidly. These materials are ideal for applications that require low density and high strength. Composite materials provide great amount of flexibility in design through the variation of the fiber orientation or stacking sequence of fiber and matrix materials. The mechanical behavior of laminates strongly depends on the thickness of lamina and the orientation of fibers. Hence, the lamina must be designed to satisfy the specific requirements of each particular application and to obtain maximum advantage from the directional properties of its constituent materials. The normal stresses and through-thickness distributions of transverse shear for composite materials are very important because in laminate composite plates, stress-induced failures occur through three mechanisms. For instance, when the in-plane stress gets too large, then the fiber breakage occurs. However, normally before the in-plane stresses exceed the fiber breakage point, inter laminar shear stress failure occurs when one layer slips tangentially relative to another. Alternatively, transverse normal stress may increase enough to cause failure by which two layers pull apart from each other. Therefore, it is imperative to understand and calculate transverse shear and normal stress through the thickness of the plate accurately. In general, two different approaches have been used to study laminated composite structures, which are: (1) single layer theories and (2) discrete layer theories. In the single layer theory approach, layers in laminated composites are assumed to be one equivalent single layer (ESL) whereas in the discrete theory approach, each layer is considered separately in the analysis. Also, plate deformation theories can be categorized into two types: (1) displacement and (2) stress -based theories. A brief description of displacement-based theories is given below: displacement-based theories can be divided into two categories: classical l aminate theory (CLT) and shear deformation plate theories. Normally, composite laminate plate theories are described in the CLT, the first-order shear deformation theory (FSDT), the global higher-order theory, and the global-local higher shear deformation theory (SDT). DESCRIPTION: In the studies carried out in last few decades, many different theories were presented to overcome various issues and explain the behaviors of composite materials more accurately. In this paper, these theories are reviewed, categorized, and their advantages, weaknesses and limitations are discussed in detail. LAMINATED COMPOSITE PLATES Classical Laminate Theory (CLT) The simplest ESL laminate plate theory is the CLT, which is based on displacement based theories. In the nineteenth century Kirchhoff initiated the two-dimensional classical theory of plates and later on it was continued by Love and Timoshenko. The principal assumption in CLT is that normal lines to the mid-plane before deformation remain straight and normal to the plane after deformation. The other assumptions made in this theory are (1) the in-plane strains are small when compared to unity (2) the plates are perfectly bonded (3) the displacement are small compared to the thickness. Although these assumptions lead to simple constitutive equations, it is also the main limitation of the theory. These assumptions of neglecting the shear stresses lead to a reduction or removal of the three natural boundary conditions that should be satisfied along the free edges. These natural boundary conditions are the bending moment, normal force and twisting couple. Despite its limitations, CLT is s till a common approach used to get quick and simple predictions especially for the behavior of thin plated laminated structures. The main simplification in this model is that 3D structural plates ( with thickness ) or shells are treated as 2D plate or shells located through mid-thickness which results in a significant decrement of the total number of equations and variable, consequently saving a lot of computational time and effort. Since they are present in closed-form solutions, they provide better practical interpretation and their governing equations are easier to solve [6]. This approach remains popular because it has become the foundation for further composite plate analysis theories and methods. This method works relatively well for structures that are made out-of a balanced and symmetric laminate, experiencing either pure tension or only pure bending. The error which is introduced by neglecting the effect of transverse shear stresses becomes trivial on or near the edges and corners of thick-sectioned laminate configurations. It is observed that the induced error increases for thick plates made of composite layers. This is mainly due to the fact that the ratio of longitudinal to transverse shear elastic moduli is relatively large compared to isotropic materials [2]. It neglects transverse shear strains, under predicts deflections and overestimates natural frequencies and buckling loads [3]. Composite plates are, subjected to transverse shear and normal stresses due to their discontinuous through-thickness behavior and their global anisotropic nature [3]. In order to achieve better predictions of the response characteristics, such as bending, buckling stresses, torsion, etc., a number of other theories have been developed which are presented in following sections [6]. Figure1. Deformation Hypothesis [Taken from class notes. Advanced Plate Theory.1] Displacement and strain field for CLT are given below: [Taken from class notes. [1]] First-order shear deformation theories (FSDT) Reissner and Mindlin developed the conventional theories for analyzing thicker laminated composite plate which also considered the transfer shear effects. These theories are popularly known as the shear deformation plate theories. Many other theories, which are extension of SDT, have also been proposed to analyze the thicker laminated composite. These theories are primarily built on the assumption that the displacement w is constant through the thickness while the displacements u and v vary linearly through the thickness of each layer. In general, these theories are known as FSDT. The primary outcome of this theory is that the transverse straight lines will be straight both before and after the deformation but they will not be normal to the mid-plane after deformation. As this theory postulates constant transverse shear stress, it needs a shear correction factor to satisfy the plate boundary conditions on both the lower and upper surface. The shear correction factor is introduced to adjust the transverse shear stiffness values and thereby, the accuracy of results of the FSDT will depend notably on the shear correction factor. Further research has been undertaken to overcome the limitations of FSDT without involving higher-order theories to avoid increasing the complexity of the equations and computations [2, 7]. Authors like Bhaskar and Varadan [23] used the combination of Naviers approach and a Laplace transform technique to solve the equations of equilibrium. Onsy et al. [4] presented a finite strip solution for laminated plates. They used the FSDT and assumed that the displacements u and v vary linearly through the thickness of each layer and are continuous at the interfaces between adjacent layers. They also postulated that the displacement w does not vary through the thickness. These assumptions provide a more realistic situation (when compared with CLPT) where in the shear strains are not continuous across the interfaces between adjacent lamina. The other limitations are (1) assumption of constant shear stress is not correct as stresses must be zero at free surfaces. (2) FDST produces accurate results only for very thin plates. In order to calculate transverse shear more accurately, to satisfy all boundary conditions and to analyze the behavior of more complicated thick composite structures under different loading condition and to overcome the limitations the use of higher-order shear deformation theories are imperative[1]. Figure2. Reissner Mindline Plate [picture taken from MAE 557 class notes. 1] Higher Order Shear Deformation Theory: The limitations of the CLT and the FSDT have persuaded the researchers to develop a number of global HOSDT. The higher-order models are based on an assumption of nonlinear stress variation through the thickness [1]. These theories are developed for thick plates but are predominantly 2D in nature. These theories are capable of representing the section warping in the deformed configuration. At the layer interfaces, some of these models do not satisfy the continuity conditions of transverse shear stresses. Although the discrete layer theories do not have this concern, they are computationally slow when solving these problems because of the fact that the order of their governing equations purely depends on the number of layers [24]. Whitney attempted to examine the problem with inter laminar normal stress [25]. Several authors were involved in developing this theory , for instance the calculation of inter laminar normal stress was studied by Pagano [26], a boundary layer theory by Tang [ 6], the perturbation method by Hsu and Herakovich , and an approximate elasticity solutions by Pipes and Pagano. In most of these models, the laminate is assumed to be reasonably long. The stress singularities were considered in a model presented by Wang and Choi. In order to determine the stress singularities at the laminate free edges, Wang and Choi used the Lekhnitskiis [27] stress potential and the theory of anisotropic elasticity. The Eigen function technique developed by them uses a collocation system at every ply interface to satisfy continuity. The major limitation of this theory is that it can be applied to only relatively thin laminates [17]. In order to explain plate deformation for composite laminate plates with thickness, Ambartsumian proposed a higher-order transverse shear stress function. Various different functions were proposed by Reddy [2], Touratier , Karama and Soldatos. The results of some of these methods were compared by Aydogdu [23]. For example, a 2D higher -order theory is developed by Matsunaga to investigate buckling in isotropic plates for in-plane loads where the effects of transverse shear and normal deformations are predicted in his study. Higher-order theories, which consider the complete effects of transverse shear, normal deformations and rotary inertia, have been studied for the vibration and stability problems of specific laminates. In general, researchers who have wanted to simulate plates have used the third-order shear deformation theories (TSDTs) which was first published by Schmidt and later developed by Jemielita. This theory is also known as parabolic shear deformation plate theory (PSDPT). Researchers like Phan and Reddy [30] applied this theory for the free vibration, the bending and the buckling of composite plates [23]. The same unknown displacements as those used in FSDT were used. This theory also satisfies transverse shear-free conditions at the outer surfaces. The results obtained show that for the thick lami nates the in-plane stresses are predicted much well than those identified using FSDT, but still these results have errors when compared with 3D models. This theory is not based on the layer-wise type, therefore, unlike most of other ESL theories, it does not satisfy the continuity conditions of transverse shear stresses between layers [9]. Vuksanovic proposed another parabolic distribution of shear strains through the laminated plate thickness which has a cubic variation of in-plane displacement. The results confirm that this model can predict the global laminate response better than previous used parabolic methods. The primary limitation is that it is challenging to accurately compute the inter laminar stress distributions [9]. In the third-order shear deformation theories assumes (1) the in-plane displacements are a cubic expression of the thickness coordinate (2) the out-of-plane displacement is a quadratic expression. Carrera presented a third-order shear deformation theory whic h based on the model which was presented by Vlasov for equation of bending plates. By imposing homogeneous stress conditions with correspondence to the plate top-surface the reduced third-order shear deformation model with only three displacement variables was obtained. This was further modified in the same research for the non-homogeneous stress conditions[6]. Figure2. Displacement field and transverse shear stress field for the various composite laminate theories. [* Figure taken from class notes. Advanced_plate_theory.pdf] Trigonometric shear deformation plate theory (TSDPT) Shear deformation plate theories which use trigonometric functions are called TSDPT. In this theory the ability to predict accurate solutions has been enhanced by combing trigonometric terms with the algebraic through the- thickness terms assumed for the displacements. Touratier [48] chose transverse strain distribution as a sine function [23]. Stein developed a 2D theory wherein the displacements are stated by trigonometric series. Stein and Jegley studied the effects of transverse shear stress on the cylindrical bending of the laminated composite plates [31]. The results obtained from these theories show that this theory calculates the stresses more accurately than other theories. Kassapogolou and Lagace used the principle of minimum complimentary energy to introduce a straightforward method to analyze symmetric laminate plates which are subjected to tension/compression [15, 16]. Afterwards Kassapogolou [28] generalized and modified this approach for general unsymmetrical laminate loads i.e. in-plane and out of- plane common moment and shear loads. The shortcomings of this model are that it does not solve the weaknesses of inequality in Poissons ratios. Becker [29] made use of cosine and sine functions for warping deformation of v and w displacement, respectively and developed a closed-form higher-order laminated plate theory. Mortan and Webber presented an analytical method which took into consideration the thermal effects in their model and by using the same approach as Kassapoglou and Becker. Lu and Liu [22] proposed an inter laminar shear stress continuity theory in which the inter laminar shear stress is directly obtained from the constitutive equations. This theory was postulated in order to develop an accurate theory for inter laminar stress analysis by considering both the transverse shear effects and continuity requirements. The drawback in this model is that the deformation in the thickness is neglected and therefore it cannot calculate the inter la minar normal stress directly from the constitutive equations. Later, Lu and Liu [21] developed the interlayer shear slip theory based on a multilayer approach model by investigating the effect of interfacial bonding on the behavior of composite laminates. Finally, Lee and Liu also derived the closed-form solutions for the general analysis of inter laminar stresses for thin and thick composite laminates under sinusoidal distributed loading. Both inter laminar shear stress and inter laminar normal stress at the composite interface were satisfied in this model and also the inter laminar stresses could be calculated directly from the constitutive equations. Touratier [20] proposed a theory based on using certain sinusoidal functions for shear stress. After comparing the results obtained numerically for the bending of sandwich plates it was shown that this theory is more accurate than both FSDT and HOSDT [17]. Hyperbolic shear deformation theory (HSDT): Soldatos proposed the hyperbolic shear deformation theory [6]. Timarci and Soldatos combined the various shear deformation theories to formulate this HSDT. The major advantage of this unified theory is the ability to vary the transverse strain distribution [19]. Authors like Ramalingeswaran and Ganesan [18] have used parabolic and hyperbolic function to uniform external pressure and a simply supported cylindrical shell for cross ply laminated composite by considering an internal sinusoidal pressure [17]. Karama et al. proposed an exponential function for the transverse strain for his study of the bending of composite [6]. Layerwise Theory (LT): (Zigzag effect) In order to present accurate results many new theories like the layerwise theory and individual layer theory have been formulated. Some of the eminent researches involved in developing these theories are Wu, Chen, Plagianakos[13], Saravanos, Fares and Elmarghany[14]. The basic technique employed in these theories is that assuming certain displacement and stress models in each layer of the composite laminates and in order to reduce the unknown variables, equilibrium and compatibility equations are defined at the interface. These theories are often computationally time consuming and very expensive to obtain accurate results due to the fact that they use many different unknowns for multilayered plates. To predict both gross response and the stress distributions accurately a number of layer wise plate models which can represent the zigzag behavior of the in-plane displacement through the thickness have been developed in the recent past. However, in the Layerwise Theories the major drawba ck is that the number of unknown increases significantly with the number of layers and consequently the computational weight becomes considerably heavier and higher. To overcome this problem, various solutions were suggested. Cho and Parmerter presented a model where in the number of the unknowns is independent of the number of layers. They achieved it by superimposing a cubic varying displacement field on a zigzag linearly varying displacement [6]. This method was very efficient as it satisfied the transverse shear stress continuity at the layer interfaces and shear-free surface conditions. The theories that have been developed to justify through-the-thickness piece-wise behavior of stresses and displacement are often subjected to zigzag theories (ZZ). The zigzag effect can be termed as the different tangential elastic compliances of the plies which cause the displacement components to show a quick change of their slopes in the thickness direction at each layer interface. To summar ize, the in-plane stresses can be discontinuous at each layer interface, while the transverse stresses, for equilibrium, must be continuous. In ZZ theory, the compatibility of the displacements and the inter laminar equilibrium of the transverse stresses in the thickness direction are assured by defining a new stiffness matrix [12]. Lekhnitskii was one of the pioneers who tried to define a ZZ theory. The main drawback for this model is the limitation of the approach to only multi-layered composite where each layer is isotropic. Ren later improved this model by using an extension of the theory developed by Reissner to multi-layered plates. This approach used a Lagrange function with five parameters, which represents the DOF of the structure. These are the set of displacement field equations used in zigzag theory. This equation are taken from the class notes, advanced plate theory [1] Mixed Plate Theory: In order to overcome the limitations of each composite laminate theory researchers have started to unify the different laminate theories. Unified equations have been proposed for mixed layer wise and mixed ESL theories. The main aim is to formulate these unified theories in the most general way for users to be able to choose from the approaches like ESL, Layer wise zigzag, etc. and at the same time choose the order of the expansion of displacements and transverse stresses. This class of model has been contemplated over the last few decades. The so-called mixed variation approach based on the variation principles developed by Hellinger was proposed and then improved by Reissner. In this theory the number of variables that must be computed should be at least 2n, where n is the total number of layers. By using the weak form of Hookes Law the number of variables can be significantly reduced, which shows the variables in terms of the three displacements only. Shimpi et al. [11] derived tw o novel formulations with only two variables, which work perfectly for moderately thick isotropic plates. The major limitation is that it requires accurately calculated shear correction factors for transverse shear stresses in multilayered composite plates. Conclusion In this literature review, various composite laminate plate theories have been categorized. The advantages and limitations of each model have been discussed in detail. This paper mainly focused on how efficiently and accurately the various models can predict the transverse shear effects. It is explained that CLT and FSDT are unable to efficiently predict transverse shear stresses of both moderately thick and thick laminated composite plates. Higher order shear deformation theories were developed in order to obtain accurate transverse shear stresses. Also, the zigzag theories satisfying inter laminar continuity of transverse shear stresses at interfaces is unable to accurately compute transverse shear stresses directly from constitutive equations. 3D equilibrium equations have to be adopted to accurately obtain transverse shear stresses which also require heavy computational processing because of the large number of variables which depend on the number of layers, they become impractic al for engineering applications. Some researchers have recently tried to use the transverse shear and warping effect in highly anisotropic composite to passively control the composite structure. Smart passive adaptive structures are a new technological approach for introducing smart and predictable composite materials with wide ranging applications. They can be used to exploit the effects of shear and elastic coupling and link stretching to bending to twisting of the structure. This requires a higher understanding and in-depth knowledge of inter laminar shear. Therefore, predicting transverse shear effect accurately and in practical way for various engineering applications is imperative.

E-Governance in Indian Banks: ICICI Bank

E-Governance in Indian Banks: ICICI Bank Before the start of my second year of PGDBM, I got an opportunity to have a corporate exposure at ICICI regional bank. In addition to this exposure, it also allowed to implement some of our course learning to real business world situations. My internship with ICICI regional bank started on 28th June and extended till 9th august. ICICI Bank is Indias second-largest bank with total assets of Rs. 3,634.00 billion (US$ 81 billion) at March 31, 2010. The Bank has a diverse network of 2,016 branches and about 5,219 ATMs in India and presence in 18 countries. They offer a wide range of banking products financial services to corporate and retail customers through a variety of delivery channels (www.icicibank.com). At my very first day, I got the opportunity to talk to some of the senior managers at my office, and they suggested me that I should see the working on their different departments and then select my department after one week. During this week, I interacted with almost every department personnel. They told me what their general day is like and what they do and how their part is important for achieving companys strategic goals. In my second week, I chose government banking group of ICICI bank, which comes under corporate banking group. Government Banking Group of ICICI bank offers world-class banking services leveraging on state of art technology platform and to meet complete financial needs of the government and its enterprises.  Their aim is to lever their advanced technology platform and ability to deliver customized solutions to meet the specific needs of each and every client emerge as the preferred banker for all government departments and corporations.(www.icicibank.com) My mentor Mr.H; relationship manager at the same department, gave me an overview about their department and how the functions. In my 2nd week of working as a management trainee to GBG, he assigned me a live summer internship project, where I was required to contact government authorities, which were falling under national E-governance plan and offer them our bank services. Route map of my project E-GOVERANCE: Foundation for better and acceptable institution mechanism Use e-governance to fight corruption- Kalam INRODUCTION E-government is the use of information and communication technology (ICT) to promote more efficient and cost-effective government, more convenient government services, greater public access to information, and more government accountability to citizens (www.adb.org). It goes beyond providing provision of online services and also, covers the use of IT for strategic planning and reaching governments development goals. It is a way by which governments use the new technologies to provide people with more convenient and reliable access to government information and services, to improve the quality of the services and also, providing greater opportunities to participate in democratic institutions and processes. E-Government provides with some tremendous opportunities to move forward in the 21st century with better quality, cost-effective, government services and a better relationship between citizens and their government. (Aggarwal, mittal et al, 2007) E-Governance is no longer an Option It is a reality and a necessity of Governance- S. Lakshminarayanan E-Governance Its relevance One click is deemed good enough to cut the much-dreaded Indian red-tape to shreds. Another one takes the wind out of all those touts hanging around public offices. Public accountability and responsive services seem suddenly just a blip way. (www.dqindia.ciol.com) Good governance is based on the premise that the laws and procedures are transparent, clearly defined understood by those governed and the implementation is also quick without any hurdles. However, the governance in a developing country like ours is a challenge, as majority of the governed (citizens) are educationally socio-economically challenged. Moreover in developing countries, the governments are formed through democratic means, the challenge of governance is much larger as the governors themselves are at times not very clear about the various rules and procedures. Also, at times, the rules and procedures are explicitly defined in the constitution or statutes, but they themselves creates hindrances in the path of governance due to lack of procedural clarities. In such a state, the answer lies in providing a mechanism that is quick, interactive, transparent and has a clear repository of rules and regulations, which provide support in decision making for both the governors and t he governed and this mechanism is e- governance, providing the benefit of being clear cut, transparent, interactive, easy to implement and aiming to provide solution in the quickest possible time frame. E-Governance, at ground level will provides three basic change potentials for good governance for development: Automation: Replacing (at least, to some extent) current human-executed processes, which involve accepting, storing, processing and transmitting information. Informatisation: Supporting current human-executed information processes. Transformation: Supporting new human-executed information processes. These change potentials, in turn, can bring five main benefits to governance for development: Governance that is cheaper: Producing the same outputs at lower total cost. Governance that does more: Producing more outputs at the same total cost. Governance that is quicker: Producing the same outputs at the same total cost in less time. Governance that works better: Producing the same outputs at the same total cost in the same time, but to a higher quality standard. Governance that is innovative: Producing new outputs. E-Governance origin The Global shifts towards increased deployment of IT (Information technology) by governments emerged in the nineties, with the coming of World Wide Web. The e-governance initiatives have come a long way since then. With the increase use of internet and mobile connections, the people are learning to exploit new mode of access in wide ranging ways. Today generation expect more information and services to be available online from government organizations to further their civic and professional lives, thus creating abundant evidence that the new e-citizenship is taking hold. E-governance originated in India during the seventies with a focus on developing in- house government applications in the area of defence, economic monitoring, planning and the using IT to manage data intensive functions related to elections, census, tax administration etc. The efforts of National Informatics Center (NIC) to connect all the district headquarters during the eighties led to a significant development in this field. During early nineties, IT technologies were supplemented with ICT technologies, for wider sectoral applications .Primarily the emphasis has been on automation and computerization, the state governments have also endeavoured to use ICT tools into connectivity, networking, setting up systems for processing information and delivering services. At a micro level, it ranges from IT automation in individual departments, electronic file handling, and access to entitlements, public grievance systems, service delivery for high volume routine transactions like payment of bills, tax etc. The thrust has varied across initiatives, while some focusing on enabling citizen-state interface for various government services, and others focusing on bettering livelihoods. E -Goverance Intiatives in India The notion of e-governance has its roots in attempts in many countries to modernise government in response to perceived citizen dissatisfaction or disengagement.(Sihna, 2006) India is a developing country with a population of about 1.2 billion spread over 28 geographically uneven states. Interestingly, transparency and citizen-centric government, expected broad outcome of e-Governance, is not new to India. The rock edicts of Emperor Ashoka, 3 Century BC provides an excellent example of this interface unambiguous and  Transparent government information was available at public place for people convenience. In most of the states in the India, people speak different languages and dialects; having varying literacy levels and distinct socio-cultural attitudes that have affected not only economic progress, but also our legislature. However, over and above, these fragmented population, there is an overlying layer of information technology professionals or knowledge workers, who seem to have indirectly pioneered e-Governance initiatives.(Aggarwal, mittal et al, 2007) The Central and State administrations, ports, customs, public tax system and education system of our country has been pioneers in e-Governance India. A number of state governments has already implemented e-Governance initiatives, which are aimed at being cost effective, while offering various facilities to citizens. National E-Governance plan The Government of India (GOI) has formulated a national program the National e-governance Plan, which is an attempt to cover all the important areas relating to e-Governance Policy, Infrastructure, Finances, Project Management, Government Process, Finances, Reengineering, Capacity Building, Training, Assessment etc. across the Central and State Governments. The plan seeks to lay the foundation and provide the impetus for long-term growth of e-Governance. Their plan seeks to create the right governance and institutional mechanisms, setting up the core infrastructure and policies and implement a number of Mission Mode Projects at the centre, state and integrated service levels to create a citizen-centric and business-centric environment for governance. The vision of this plan is to make sure that all Government services are accessible to the common man in his/her locality through common service delivery outlets. The implementation strategy envisages clear definition of service goals and metrics for each project and structured stakeholder consultations with all stakeholders including citizens and civil society organizations before the service goals of each project are firmed up.( Das Chandrashekhar, 2007). (Source: Das Chandrashekhar, 2007) The above diagram give E-Governance framework that includes back-end (databases of different government agencies, service providers, state governments etc.), middleware and front-end delivery channels (PCs, mobile phones, kiosks, integrated service centers etc) for citizens and businesses. The middle-ware comprises of communication and security infrastructure, gateways and integrated services, aimed at facilitating integration of inter-departmental services. Challenges of e-Governance in India Sharma (2002) points out that the culture of governance in India has been characterized by secrecy, seniority and corruption. These need to be addressed with a vengeance if the grand vision of e-Governance across India has to become a reality (Agarwal Mittal et al,2003). The initiatives taken are more focused on government department, automaton rather than anything to do with the citizens. They might solve a number of problems of government employees but not even a single solution is totally focused on citizen thathas come up in India. Indian citizens are still forced to move from one department to another,and from one table to another in order to get their work done. In lieu of this, the National Task Force has also made several recommendations. The fundamental strategic challenge faced is e-Readiness for e-Governance It is a multifold challenge posing basic questions like: Is required Data Systems Infrastructure Ready? Is required Legal Infrastructure Ready? Is required Human Infrastructure Ready? Is required Institutional Infrastructure Ready? Is required Technological Infrastructure Ready? Is required Leadership and Strategic Thinking Ready? Role of banking in E-goverance Indian banking sector through its network of over 74,000 branches provides efficient and swift cash management and payment mechanisms ensures timely availbility of the funds to the ultimate beneficiaries.- RP Sihna, Deputy Managing Director (IT), State bank of India E-goverance goes beyond provision of online services and includes,the use of IT for strategic planning and reaching development goals of the government to the citizens. Government prime concern is that the revenue deposited at various branches of banks throughtout the country are collected expeditiously and every rupee spend on the social sector plans schemes reaches the intended beneficiaries quickly and directly. It is therefore, imperative that the indian banking sector which have a wide network af over 74,000 branches provides efficent and swift cash management system and payment mechanisms to ensure timely availability of the funds. Banks apart from taking the technology beyond urban centers to remote areas,that are still unbanked and underserviced,but also serving as a channel for credit delievery and innovative products to the poor and underprivileged sections of society. With an efficent deployment of technology, banks can step in and provide access to banking facilities like opening of accounts, money transfer services,payments of bills etc. Banks provide payment solutions to conduct E-payments with government departments using smart cards/credit cards or making a direct debit from their account (Internet banking) when the due date falls. In short, bank can help in the process of E-Goverance by 3 methods: ICICI government banking group its E-Goverance intitatives The government banking group of ICICI,falls under their corporate banking group and it specifically cater to the government entities and institutions. We ensure compliance of specific regulatory requirements while customizing these products and services for the government. Our constant endeavor is to fulfill the specific objectives of the government at various district, state, and national levels.(www.icicibank.com) Agency Function Their are the accredited Banker to the Ministry of Civil Aviation. All payments and receipts of this Ministry across the country are routed through their network. They are the approved banker to collect direct taxes as well as indirect Taxes for the central Government and states sales taxes/ VAT in the States of Delhi, Punjab, Andhra Pradesh and Gujarat. Approved bank for disbursement of pensions for central government and defense employees. E-Goverance Intiatives Online Collection of fees for Director General Foreign Trade (DGFT) Online collection of fees and Stamp duty under MCA-21 Limited Liability Partnership (LLP) E-ticketing initiative for Indian Railways Online Funds Disbursement and Tracking System for Ministry of Health and Family Welfare (MoHFW) E-goverance intitative undertaken by me as a summer trainee (live) in ICICI bank My mentor gave me a project where I was required to study different government authorities and departments falling under E-Goverance plan of government of India,to select one authority where ICICI bank can fit in and offer them their services and also, explaining how it will be benefical to not only them , but also to the citizen on the receiving end. As I was placed in Delhi corporate office, I thought it will be good idea to start exploring the authorities which wall under Delhi. My mentor, Mr.Hitesh Setya, also considered it as a good idea as it was easy to talk and even meet these authorities. Delhi Government Departments cover health, revenue tax, audit, arts culture, transport, administrative reforms, health and family higher education, IT, Gurdwara elections, administrative reforms agricultural marketing, Fire service economics and statistics,health and family,industries and many others. (A comprehensive lists of the department has been given in the appendix). All the departments of Delhi government works for enhancing the socio-economic viability of the city. Each and every Delhi department is entrusted with a separate set of responsibilities and duties. I studied almost every department falling under delhi government authority and saw the scope of E-goverance in those departments.After working on this for a period of 2 weeks,I came down to the following authorities names: Transport department Delhi Development Authority Delhi tourism Delhi passport authority After contacting these agenices and meeting their respective officals ,I narrowed with DDA (it looks after the orderly-yet-rapid development of Delhi),as they are already in the process of making their database and this department has a bad reputation when it come to red tapism and bureaucratic attitude .Under this department,a number of activities are taken care of ranging from tenders, housing,buildings ,various registrations etc.I needed to select one major activity which will become my reports focal point.I selected DDA procedure for conversion from leasehold to freehold . DDA-SCOPE FOR E-GOVERANCE Delhi Development Authority (DDA), time moves at its own sweet, slow pace. And in order to get your work down, you need an athletes stamina and a monks patience (Roy,hindustan times,2010) The Delhi Development Authoritys (DDA) was established in the year 1957,and nearly after 50 years of existance ,it has come out with a grand vision for 2010: to become a high performance and people friendly organisation. This mission comes not a year too soon for the land development agency.The authority referred itself as the citys ninth builder, touches the life of almost every second Delhiite.Since its initiationin 1957, DDA has worked towards the development ofthe city and has created or facilitated about 1 million dwelling units to date. including allotment of more than 3 lakh flats, plots to Cooperative Groups and residential plots .Apart from the construction of 600 big and small commercial centres and allotment of industrial and institutional plots.DDAs dreary and dusty file-laden headquarter, Vikas Sadan, gets nearly about 700 visitors daily.(Roy,hindustan times,2010) The crowd thronging at the the DDA offices explains that it is not easy to own a DDA flat or plot,which the authority sells at affordable rates.Whats even tougher than this ,is getting the possession letters, conversion from leasehold to freehold or even changing the title deeds. Add from sumwhere else In the labyrinthine corridors of the DDA office, files journey begins from one table and then meanders through at almost all the tables of the office and this journey in the can take anything from a month to years. The DDA babus take ages to move files and the smallest lacunae in your documents can slow the process by months. DDAs citizens charter promises disposal of transactions a specific time frame of between 15 and 90 days. These promises, however, remain cosily embedded in the glossy booklet. This is where the touts come in. For a handsome feeanything between Rs 40,000 to Rs 1 lakhdepending on the `complexity of your case, touts can speed up the process of getting your job done. Thanks to DDAs initiatives to curb the tout menace, these assistants-for-hire can now be found lingering in the parking lots and small photostat shops and eateries outside Vikas Sadan. We can get any job done as we have a `setting with officials inside the building, says a tout, who doesnt wish to be identified. The rates have gone up though as DDA has become stricter about these things now. Unless you have deep pockets, getting your application approved from the DDA is next to impossible, says Umesh Sharma (name changed on request), who has been trying to transfer his flat from his fathers name, who died many years ago, to his own for the past six years. Every official expects to be bribed and you have to grease many palms. The officials say the property we bought for a few thousands decades ago will now sell for lakhs but they dont stand to gain anything from it, he said. If you are transferring a property to your name or converting it from leasehold to freehold to sell it, they want their share, Sharma said. TOMORROW The passport office is a riddle. Theres paperwork, there are meetings and a single error can deboard your plans. COVERAGE E goverance in India has touched various areas like income tax,passport,pensions,company affaris, police,municpalities ,ariculture ,central excise and many more.In my report ,we will be dicussing three main areas namely, Sales/Commercial Tax Department(VAT),MCD (Municipal Corporation of Delhi) NDMC(New Delhi municpal council) , income tax department. B.MCD NDMC The National Capital Territory of Delhi (NCT) comprises three local bodies, MCD, NDMC and Cantonment Board. The MCD comprises of about 96 per cent of the area and population of the Union Territory (UT)of Delhi. The Delhi Municipal Corporation Act, 1957 was amended in August, 1994 to bring it in tune with the Constitutional provisions of Part IXA. In respect of New Delhi Municipal Council, which consists of only 3 per cent of the area and 3 per cent of the population of National Capital Territory of Delhi.( http://www.ndmc.gov.in/AboutNDMC/NAboutus.aspx) (ii) NDMC 1. Grants: 2. Public: 2.1 Property tax :The Property department is one of the tax revenue-earning departments of NDMC. Revenue is realized as (i) property tax from about 12,000 private properties and Government properties constructed prior to 26th January, 1950 and (ii) service charges from the government properties constructed after 26-01-1950. Property tax is an obligatory tax levied on all lands and buildings in New Delhi. It is a percentage of the rateable value of lands and buildings. The rates of taxes are determined by the Council from year-to-year basis. Facilities available online: Application Procedures http://www.ndmc.gov.in/services/PropertyTax/Images/img_bullet.gif Download-Forms http://www.ndmc.gov.in/services/PropertyTax/Images/img_bullet.gif Rate List/ Method of Calculation of Property Tax APPENDIX transport department irrigation and flood control department planning department SC/ST/OBC/Minorities welfare department informations and public relations department industries department land and building department police department forest department administrative reforms department directorate of audit economics and statistics department chit fund department art, culture and language department directorate of education directorate of training and technical education environment department development department health and family department excise, entertainment and luxury tax department public works department weights and measures department sales tax department tihar prisons services department directorate of prevention of food adulteration directorate of agricultural marketing labor department social welfare department

Penelope and Odysseus of Homers Odyssey Essay -- Homer Odyssey Essays

Penelope and Odysseus of Homer's Odyssey    Penelope and Odysseus, being kin spirits, soul mates, and a great husband and wife in their own right, are very much alike.   They have many of the same qualities.      Ã‚  Ã‚  Ã‚  Ã‚   Both Penelope and Odysseus are very quick thinking and cunning.   Odysseus, for example, devises the plan to get the Cyclops to drink the wine so the crew could stab him in the eye.   Another example of Odysseus' cunning is his elaborate plan to massacre the suitors.   Odysseus orders that all the weapons be taken out of the room where the arrow contest was being held, then that the women of the household to be locked in their rooms, as to not interfere, then for the doors to be locked by his allies, then to...

Educational Reform in a Pluralistic Society :: Teaching Education

Educational Reform in a Pluralistic Society My personal philosophy of education is that every child has the right to an education. This education should be such that every student has the equal opportunity to succeed and learn at the highest level they are capable. I believe that the purpose of education is to educate people who are well-rounded individuals. By well-rounded, I am referring to graduates who will be able to apply their education to numerous aspects of life. This includes people who are going to college and people who will be entering the work force directly from high school. Every person should have a wide base of knowledge to draw from and add to throughout their life. This type of education allows those who wish to pursue a higher education to draw upon their education in a more intellectual way, and those that choose to work can draw upon their education in a more â€Å"practical† way. Those people who do not pursue education further will still have a knowledge base that allows them to view many aspects of life with an open mind. A second reason I believe that education should be geared toward creating well-rounded individuals is that I think this will greatly improve the state of our nation. A majority of our most productive, happy citizens are those ho have had a wide variety of experiences and have a broad knowledge base. Being able to accept many differences that occur throughout the human race occurs more readily among those with a broad educational background. When deciding what level of government should be responsible for education, I believe that the primary responsibility should rest on the federal government. The role of the federal government should be to regulate the standards of education. This should include monitoring every school in the United States of America to make sure that all students are receiving comparable education. As a result, curriculum standards should be set at a national level. The federal government should keep a establish a national council to decide the standards for each subject area. Representatives from each state would be appointed to monitor their own state’s progress. At the state level, state appointed committees would oversee the progress of the national curriculum. State committees should decide which textbooks will be adopted. By letting states adopt their own textbooks, this keeps some local control. On a local level, each school district would be responsible for deciding how the federal curriculum standards should be implemented. I believe that every school should strive for both excellence and equality in public education.

Admiration Of Anne Bradstreets :: essays research papers

Admiration of Anne Bradstreets values as compared to those of Ben Franklin and Johnathan Edwards The relationships that people have with others has a severe impact on that person’s life, albeit many are good, some, though, are bad. How we choose to form, maintain and use these relationships is up to us, just as what they mean is up to us too. I will show the relationships of some writers and how they treat others, as an important value to me. Three writers of our era, Benjamin Franklin, Jonathan Edwards, and Anne Bradstreet are most notable with their relationships with people. My thoughts on Benjamin Franklin’s work were unfortunatly on the negative side. To sum his writings up, they were long, boring and not concise. His writing varied heavily. He was known for writing on one topic and then changing to another then skipping to yet another. The following paragragh is an exerpt of his writing’s to show the long, varied writings that changed from subject to subject: “I have been the more particular in this Description of my Journey, and shall be so of my first Entry into that City, that you may in your mind compare such an unlikely Beginning with the Figure I have since made there. I was in my working Dress, my best Clothes being to come round by sea. I was dirty from my journey; my pockets were stuff’d out with shirts and stockings; I knew no Soul, nor where to look for lodging. I was fatigu’dwith Traveling, Rowing and Want of Rest. I was very hungry, and my whole stock of cashconsisted of a Dutch Dollar and and about a Shilling in Copper. The latter I gave the People of the Boat for my Passage, who at first refused it on Account of my Rowing; but I insisted on their taking it, a Man being sometimes more generous when he has but a little Money than when he has plenty, perhaps thro’ the Fear of Being thought to have but a little. Then I walked up the Street’ gazing about, till near the Market House I met a boy with bread…'; (p. 241) Because of the skipping around, to often unrelated topics, it is very difficult to pay attention, read and keep straight as to what is Franklin’s point. One could almost call the style of writing a form of rambling. From Franklin’s work one is able to deduce that he is a good man with good intention and is a upbeat and optimistic person but he doesn’t really care for people and treats them like object and tools.

Causes of Prejudice

Prejudice is an opinion that is not based on actual evidence or experience. In â€Å"Causes of Prejudice,† Vincent Parillo describes the psychological and sociological reasons of prejudice. Among these causes, frustration is defined to produce a prejudicial attitude towards others. Parillo explains in his work that throughout history, minority groups have been used as scapegoats to take the blame for certain events. He clarifies that scapegoating is the act of blaming others for an incident that is not their fault.This idea is also visible in the novel To Kill a Mockingbird by Harper Lee, in the art where a lawyer named Atticus tries to prove an African American innocent who has been falsely charged with raping a white woman. Therefore, both Parillo's â€Å"Causes of Prejudice† and Harper Lee's To Kill a Mockingbird support that frustration is a cause of prejudice because of an increase in aggression towards a scapegoat. To begin with, frustration is caused by relative deprivation, which is the lack of resources in an individual's environment when compared to others.This results in aggression towards a scapegoat in order to relieve this tension. â€Å"Frustrated people ay easily strike out against the perceived cause of their frustration. However, this reaction may not be possible because the true source of the frustration is often too nebulous to be identified or too powerful to act against† (Parillo 583). His view is also seen in To Kill a Mockingbird, when Mayella Ewell claims Tom Robinson has raped her. Atticus tries to prove to the Jury that Tom Robinson in fact did not rape Mayella and that she, a white woman, kissed Tom, a black man.Mayella is an Ewell; a very poor family in the town of Maycomb and therefore she has to live through tough onditions which include living behind the garbage dump, barely having any money to support her dad and seven siblings, as well as being beaten by her own father. Most importantly, she is frustrated t hat she always feels dissatisfied with her life since she was never able to experience any happiness by being isolated from the rest of the world. Therefore, she tries to at least kiss a black man to feel some sense of happiness.When she realizes it is condemned by society, her frustration increases partly because society is not allowing her to have a small amount of happiness, and o she shows her aggression by blaming Tom Robinson for raping her. In addition, aggression resulted from frustration is pinpointed towards scapegoats because they share similar characteristics of being vulnerable to blame. â€Å"The group must be (1) highly visible in physical appearance or observable customs and acations; (2) not strong enough to strike back; (3) situated within easy access of the dominant group .. † (Parillo 584). To Kill a Mockingbird takes place in southern Alabama in the 1930's. This was the time period where prejudice against African Americans was present. Segregation was pre sent because having white skin was een to be better than having black skin. This simple difference in skin color resulted in an unfair treatment of African Americans. Separate bathrooms, drinking fountains, churches, and schools resulted for African Americans and whites. Also, since whites felt that the blacks were inferior to them, they tended to assume all blacks were unintelligent.When Mayella copes with her frustration of being isolated from the rest of the world by blaming Tom Robinson, the court looks at his skin color instead of the evidence given tor this case. Even though Atticus provides plenty ot evidence that roves that it was impossible for Tom to commit the rape of Mayella, Tom is still found guilty because even if Mayella is part of the lower class of Maycomb, she is still a white woman, making her superior to Tom Robinson.It is evident that frustration plays an important role in determining prejudicial attitudes. Both the novel To Kill a Mockingbird by Harper Lee and â€Å"Causes of Prejudice† by Vincent Parillo, agree that frustration is caused by relative deprivation and when aggression forms, the blame is placed on scapegoats. These scapegoats share similar characteristics which allow them to be vulnerable to the blame that falls upon them.

Meteors Case Study Essay

Meteorites are rocks from space, which land on Earth, attracted by her gravity. The shooting stars that you see at night, are actually burning meteors that fall on Earth from outer space! This is the first of many interesting facts that are going to follow. Why do meteorites fall? For the same reason why anything falls on Earth – ‘Gravity’. Very few can escape it! Meteorites have their origin in outer space. They are relatively small pieces of dust and debris, usually left behind in the wake of a comet. Meteorites, that are huge in size, have their origin in space, as asteroids. They are left over pieces of matter from formation of the solar system, which could not clump together to form a planet like our Earth. There is a dense belt of such asteroids outside the orbit of the planet Mars, called the ‘Asteroid Belt’. Asteroids are huge in size and their lengths can number to kilometers! Once in a while, small pieces of rock or dust, come into range of Earth’s gravitational pull and fall on Earth as shooting stars. An asteroid dislodged from its trajectory and falling on Earth is also called a meteorite. However, an asteroid being huge in size, causes a cataclysmic explosion on Earth on impact. Origin ‘Meteor’ and ‘Meteorite’ facts are interchangeable terms and we shall see why they are so. When these rocks and pieces of dust are floating in space, they are called ‘Meteoroids’. When they make a blazing entry into Earth’s atmosphere, they are called ‘Meteors’. Finally, if they survive the burning entry into Earth’s atmosphere and fall on Earth, they are called ‘Meteorites’. So a meteorite could originate from comet debris called meteoroids or larger objects called asteroids! Here are some basic facts about meteorites, meteors and meteoroids. Comets leave tons of dust and debris in their trail as they travel along long orbits round the Sun. When Earth, while revolving around the Sun, passes through some patches of this comet debris, it enters the Earth’s atmosphere causing meteor showers. Meteor showers are periodic events. One can see thousands of meteors or shooting stars, as they are called, dur ing such a shower. The most popular meteor showers are ‘Perseids’ (which peak around August 12) and Leonids (which peak around 17 November). During these showers, you can observe a shooting star at the rate of 1 meteor per minute on an average. A falling meteor can travel at speed of as much as 44 miles per second ! One of the facts is that they have some of the oldest rocks in the solar system among them. They could be older than the Earth and date from the period when Sun was forming! Every day, about 4 billion meteoroids fall on Earth! Majority of them are very tiny and therefore do not cause much harm. If a meteorite is observed while falling and recovered from the place of fall, it’s called a ‘fall’ meteorite. If a meteorite is not observed while falling, but found from any location, it’s called a ‘find.’ Till 2006, there have been roughly 1,050 witnessed falls while there are about 30,000 documented ‘Finds’. Falling meteors which are large in size, can create an intense electromagnetic pulse, which temporarily disrupt radio communication in the region of fall! With a properly designed radio antenna, you can actually ‘hear’ meteorites falling as radio noise. Types and Composition Here are some facts about their types and composition, that you should know about. Recovered meteorites are classified into three main categories which are ‘Chondrites’ (Make about 86% of all recovered meteorites), ‘Achondrites’ (8%) and ‘Iron’ meteorites (6 %). The name ‘Chondrites’ comes from features called ‘Chrondules’, which are melted silicate materials from their past. Chondrites are about 4.55 billion years old and are the types of rocks from which our own planet formed! Certain chondrite meteorites fallen from outer space contain traces of amino acids and organic matter, bolstering the theory that life may have been planted on Earth! This is one of the most astounding facts. Achronidtes are relatively younger meteorites of the igneous rock type and are pieces of asteroids, the Moon and Mars! Iron meteorites are composed of iron-nickel alloys and silicate materials. They are also thought to be pieces of asteroid s! Every one of these meteor facts are intriguing. Earth has been pounded by the impact of many meteorites, ranging from the very tiny to gigantic meteorites. The meteorites impact craters that are found on earth are testimony to this. It is time for the last of our facts. One gigantic meteorite impact occurred millions of years ago on Earth which brought on the extinction of dinosaurs! One question that may come to your mind is, ‘Where do meteorites fall?’. They could fall anywhere on Earth. Meteors have been found all over the world. The recent findings have been mostly in Africa and accessible parts of Antarctica. If you could find one, you are bound to be rich as private collectors and museums pay millions of dollars for them! The reason is that they are very rare and are made up of minerals, which are never found on Earth! So keep looking! You may never know, when one might pop out of the sky, making you rich. So it’s actually profitable to know some meteor facts. Originating in the outer space, an object reaches Earth and gets a place in the list of meteorites. There have been many instances of extraterrestrial bo dies impacting the Earth’s surface while some have only passed through the Earth’s atmosphere before they were destroyed. Meteorites have been arousing interest of the masses as there is an element of mystery that surrounds them. Where do they originate? What makes some of them enter the Earth’s atmosphere? How dangerous can they get? Space research and astronomy have revealed some interesting information about some of these questions and researched thoroughly on the different types of meteorites. Most of the meteorites disintegrate before reaching Earth while some reach the planet’s surface. Huge meteorites form craters on Earth while the smaller ones involve less danger. Meteorites containing small round particles are known as chondrites and form about 86% of those falling on Earth. Those similar in appearance to small igneous rocks are called achondrites and believed as being the crustal material of asteroids. Meteorites originating from the core of asteroids are known as iron meteorites and form about 5% of the meteorites, which fall. History has recorded a number of instances of meteorites impacting the Earth. ALH 84001: It was found in the Allan Hills, Antarctica in December 1984. Meteorite hunters of the United States working on ASMNET project discovered this meteorite. When discovered, its mass was 1.93 kilograms and its rock was reportedly one of the oldest forms. This meteorite was supposed to have come from Mars. Later it was believed to consist of some traces of the life on Mars and this made ALH 84001 more famous than ever. Hoba: This meteorite lies on the farm Hoba West in Namibia and has never been moved elsewhere because of its exceptionally greater mass. With a mass of about 60 tons, it is the largest meteorite known to mankind. It is tabloid in shape and composed of metal. It is believed to have landed on Earth about 80,000 years ago. In 1955, it was declared as a national monument and has since then been attracting visitors from different parts of the world. Tunguska Event: The Tunguska explosion took place in June 1908 near Tunguska River, now a part of Russia. Most probably, the air burst of a large meteorite caused this explosion. The energy emitted from this explosion was about 1000 times greater than that of the bomb blast of Hiroshima. According to the eyewitnesses of this explosion, the event started with a flash of bright blue light and a sound originating from east and moving northward. Later the sound was accompanied by shock waves that broke windows miles away. This was one of the famous disintegrating meteorites that remain in the list of world’s most famous meteorites. Willamette Meteorite: This is an iron-nickel meteorite that was discovered in the United States near Oregon. It is the largest of the meteorites found in the United Sates as also the sixth largest in the world. Probably the meteorite had landed in the region, which is now known as Canada. This meteorite weighing about 15.5 tons is one of the very large meteorites of the world. Orgueil: This meteorite fell in France in 1864 and is a relatively older meteorite. The fall of this meteorite consisted of small stones that covered a massive area. This is one of those eight meteorites that belong to the CL chondrite group. A striking feature of this type of meteorite it that its composition is similar to that of the Sun. This meteorite is one of the most researched ones. For purposes of deeper study of the composition of this meteorite, it was split into pieces. Currently, it exists in the form of pieces kept in different museums in Europe and the United States. These were some of the famous meteorites of the world. They have always been a subject of interest for researchers around the world. Meteor showers A meteor shower is a celestial event wherein it is observed that a group of meteors radiate from anyone point in the sky. This phenomenon is also known as ‘Meteor Storm’ or ‘Meteor Outburst’. The meteors that are present in the showers are actually cosmic debris that enter the Earth atmosphere at very high speed and vaporize very quickly due to friction leaving behind a streak of light which is known as the meteor shower. An identified meteor shower is usually an annual affair as the Earth will encounter the same meteors at approximately the same time and same speed every year. Causes Meteor showers are a result of interaction that takes place between the planet Earth and a comet. Comets consist of ice and rocks (often termed dirty ice balls) that orbit around the sun like planets. Every time the comet gets close to the sun, some of the ice present in the comet melts which produces a large amount of debris. This debris moves away from the comet and becomes a part of its tail which is visible part of the comet. The solid parts of the tail are the meteoroids and they spread along the entire orbit of the comet which is termed as a meteoroid stream. As the Earth orbits around the sun, its path may cross the meteoroid stream and a meteor shower follows. When the meteoroid stream is particularly dense, then we get to witness the meteor storm and having witnessed one myself, I can guarantee that the sight is truly spectacular. People Behind the Concept It is believed that Irish astronomer George Johnstone Clooney collaborating with the British astronomer Arthur Matthew Weld Downing and Adolf Berberich belonging to the Royal Astronomical Computation Institute in Berlin, Germany offered the very first idea of the meteoroid stream in the 1890. They were able to calculate as to how the meteoroids once freed from the comet would travel at low speeds when compared to the comet itself would start drifting after completing one orbit. This effect was attributed to simple orbital wherein the materials drift laterally away from the comet as some particles make a wider orbit when compared to other particles. The gravitational pull of the Earth’s atmosphere would decide where the dust trails would pass the Earth’s atmosphere. It is a fair possibility that some years, the dust particles can completely miss the Earth’s orbit. Major Meteor Showers If you want to watch meteor showers then the best time of the year is the night of January 3. The shower has been named Quadrantids and this particular shower can produce over a close to 140 meteors per hour. The source of this shower is not a comet but a minor planet, 2003 EH1 which suffered a catastrophic breakup in 1490. However, the showers are very faint and the peak hours last only for a few hours. Hence, you will have to be in a good spot and at an ideal point to watch the shower in all its glory and the best place to watch this particular shower is from the Northern Hemisphere. But people in Southern Hemisphere need not be disappointed. As a matter of fact, they get to witness a meteor shower termed Eta Aquarids which consists of debris from the famous Halley’s Comet. This shower peaks on the night of May 5 and the rate of meteors is about 30 per hour. The meteor shower ‘Geminids’ is considered to be the best annual shower. It peaks around the night of December 13 and the rate of meteor is around 70 per hour. The source of this shower is also a minor planet, 3200 Phaethon. It is best visible from the Northern Hemisphere and it is believed that due to the extreme cold conditions, the air tends to be more transparent and this is the reason as to why this particular shower is spectacular. Sporadic Meteor Showers When the meteoroids collide with each other and can become a part of the sporadic meteors background. They form isolated meteors and are not a part of any shower. Asteroids Asteroids are considered to be remnants of an early broken planet of the solar system. Asteroids have no fixed shape and are too small to be spherical in shape. They are ellipsoids (two dimensional figure), dumbbell or irregularly shaped. As they have different shapes, they also vary in their size. The first asteroid Ceres, discovered in January 1801 by Italian astronomer Giuseppe Piazzi, is the largest known asteroid and is 940 km in diameter. Some of the smallest asteroids are just 6 meters in diameter. The mass of all the asteroids added together, is believed to lesser than the mass of the Moon. Only 200,000 asteroids have been discovered so far, but billion more undiscovered asteroids still exit in our solar system. Asteroid Belt Most asteroids lie in the asteroid belt between Mars and Jupiter, however there are more belts in the solar system, namely the ones beyond Neptune’s orbit. The belt itself has interesting origination theories. Most astronomers believe that the belt is a broken planet, while some say that the belt is primordial material that never coalesced into a planet because of Jupiter’s gravitational pull. The asteroid belt lies between the orbits of Mars and Jupiter and contains more than 200 asteroids larger than 100 km in diameter, and more than 750,000 asteroids with diameters larger than 1 km. Most asteroids are found in this belt because of the gravitational interaction between the solar system and the celestial bodies in it. As opposed to the fiction made popular by various depictions of the asteroid belt, it is not at all dense. The region is so vast that asteroids are hundreds of thousands of kilometers away from their closest neighbor. The asteroids are so small and far away from each other that they appear as faint stars, and except for Ceres, are not bright enough to be seen without some telescopic aid. Only the asteroid Vesta, on rare occasions of an extremely clear dark sky can become visible to the naked eye. What are Asteroids Composed Of? Asteroids are made of different minerals and substances. This depends on the planet they broke away from in a collision, as well as the chemical reactions they might have experienced while orbiting in the solar system. The asteroids closest to the Sun are mostly carbonaceous and the ones further away are composed of silicate rock. The metallic asteroids are made of 70-80% iron and the remaining is nickel with many other metals such as iridium mixed in. Some are also made of half silicate and half metallic. The asteroid Ceres is composed of a rocky core covered by an icy mantle, whereas Vesta has a nickel-iron core, basaltic crust and a covering of magnesium iron silicate (olivine mantle). Asteroids composition has been classified as the following: C class asteroids: They are found in the Earth’s outer belt and are darker and more carbonaceous than the ones found in the S class. D class asteroids: They are also known as Trojan asteroids of Jupiter and are dark and carbonaceous in composition. S class asteroids: They are found in the Earth’s inner belt, closer to Mars and are composed of mostly stone and iron. V class asteroids: They are a far-out group of asteroids that follow a path between the orbits of Jupiter and Uranus, and are made of igneous, eruptive materials. A near-Earth asteroid collided with the Earth about 65 million years ago, which triggered environmental changes, leading to the extinction of the dinosaurs. This asteroid created a huge circular depression called the Chicxulub Basin and is centered in Mexico’s Yucatan Peninsula, a major tourist attraction. Though the chances of asteroid collision with the Earth is very rare, they do come very close to our planet due to collisions and gravitational tugs on the highly elliptical Sun’s orbit. Most asteroids burn up in the atmosphere and never reach the Earth. NASA projects, such as the Lincoln Near-Earth Asteroid Research (LINEAR) and the Near Earth Asteroid Tracking (NEAT) main objectives are to detect and intercept asteroids or other celestial bodies coming close to the Earth before they cause untold damage to our planet. Asteroids are small celestial bodies composed of rock and metal, that revolve around the Sun. Their size can vary: some asteroids are large and roughly spherical in shape, due to which they appear like miniature planets; while the others are small and irregularly shaped. The matter of these celestial bodies also differs. The asteroid ‘Vesta’, is believed to have a nickel-iron core, olivine mantle and basaltic crust, while the asteroid ’10 Hygiea’ is composed of carbonaceous chondrite. Most of the small asteroids are piles of rubble held together by gravity. Some asteroids supposedly have traces of amino-acids and other organic compounds, and it is assumed that the impact of asteroids on the Earth could have initiated life on the planet by seeding it with the necessary chemical substances. Although, it is believed that the asteroids may have planted life on the Earth, they are capable of having catastrophic effect on the planet as well. Asteroids with a diameter of 5 to 10 meters, and energy equal to 15 kilotons of TNT, enter into the Earth’s atmosphere approximately once every year; while, those with a diameter of over 50 meters enter the Earth’s atmosphere approximately once in a thousand years. Their impact can be devastating if they hit the Earth, but they disintegrate in the upper atmosphere and most of the particles are vaporized, thus rendering them harmless. In the distant past, our planet has experienced a massive climate change and large-scale extinction of animal and plant species, ascribed to the impact of some large asteroids on the planet. The exogenesis theory suggests that origin of life on the Earth must have been triggered by the impact of some asteroid, carrying organic chemicals needed to initiate life form. The Cretaceous-Tertiary extinction event, which led to the end of dinosaurs and the Permian-Triassic extinction event that led to the end of the Permian period finishing off 90% of the species on the planet, are believed to be the result of an asteroid impact on the Earth. The craters on the solid bodies in the solar system, which were attributed to volcanic activities till 1960s, were actually formed due to the impact of celestial bodies. Researchers have determined that in the last 600 million years, 60 objects with a diameter of five km or more, have struck the Earth. Even the smallest of these object possessed energy of ten million megatons of TNT, and would have formed a crater, approximately 95 km in diameter, on the surface of our planet. The Rio Cuarto craters in Argentina are believed to have formed due to the impact of asteroids that struck this area around 10,000 years ago. In 1490, ten thousand people reportedly lost their lives due to a hail of stones from the sky. This hail of stones is assumed to be result of the disintegration of a large asteroid, after it entered the Earth’s atmosphere. In 1908, a mid-air explosion of an asteroid destroyed 80 million trees, within an area of 830 miles, near the Podkamennaya Tunguska River, in Si beria. In many cases, the sighting of a foreign body, such as an asteroid or a meteoroids is reported as a fireball in the sky. Millions of asteroids will pass by the Earth in the years to come. Though, they are unknown now, they are detectable as they come closer to the planet. The Lincoln Near-Earth Asteroid Research (LINEAR) and the Near Earth Asteroid Tracking (NEAT) are projects initiated by NASA to detect asteroids or other such foreign bodies coming close to the Earth. The need of the hour is to develop an intercept system in space, to destroy or deflect foreign objects heading towards our planet, before they prove catastrophic. Asteroids are celestial bodies consisting of rocks and metals. They are mainly concentrated in the region known as the asteroid belt which lies between the orbits of Mars and Jupiter. Asteroids can be as big as Ceres, which is close to 1000 kilometers in diameter, or can be just a few feet in diameter. Whatever the size, asteroids are neither big enough to be called planets nor are they as small as comets. They are classified as minor planets that include the Kuiper Belt Objects. Discovery On January 1, 1801, Giuseppe Piazzi discovered the first asteroid which he initially thought to be a comet. He named this asteroid Ceres, after the Sicilian Goddess of grain. Ceres is also the largest asteroid to have been discovered so far. Soon, other large asteroids like Pallas, Juno and Vista were discovered. By the end of the 19th century, several hundred asteroids were discovered. Formation of Asteroids It was once believed that asteroids were formed by the explosion of a planet orbiting between Mars and Jupiter. However, according to present day astronomers, asteroids are debris left behind by the Big Bang that could not come together to form a tenth planet because of the effect of Jupiter’s gravitational pull. Asteroid Hits Asteroids have been hitting the Earth since millions of years. However, due to the friction with Earth’s atmosphere most of the asteroids get burnt. The asteroids that enter the Earth’ s atmosphere are called meteors while the ones that get burnt and appear as shooting stars are called meteorites. According to the Giant Impact Theory, the Moon was created when Theia, an asteroid of the size of Mars, collided with the Earth in the early days of the solar system. However, some consider Theia to be more of a planetoid than an asteroid. The largest crater caused by an asteroid hit is the Chicxulub Crater in Mexico that is 180 km in diameter. The asteroid that formed the crater had a diameter of 10 km. This collision is supposed to be responsible for the extinction of a large number of flora and fauna including the dinosaur. However, the evidence of the largest asteroid hit is in the Vredefort crater in South Africa that is 300 km in diameter. Impacts of Asteroid Hits The damage that an asteroid’s impact can cause depends mainly upon its mass and velocity, as these are the two factors that determine the energy that is released when an asteroid hits the Earth. While some asteroids are capable of sending thermal waves that can incinerate most flora and fauna within a few hundred kilometers, some larger asteroids can create huge impacts causing magma to cover areas as big as continents. The worst effect of an asteroid hit is the blocking out of sunlight for months together due to formation of dust clouds and soot in the upper atmosphere. This would hamper the green plants’ ability to prepare food through the process of photosynthesis and the food chain would be disrupted. Near-Earth Asteroids Near-Earth asteroids are those that have moved closer to the Earth’s orbit as they have been knocked out of the asteroid belt due to collision with other asteroids or comets, or due to the gravitational forces of Jupiter. They are classified into the following three groups: The Amors: These are near-Earth asteroids that cross the orbit of Mars but do not go out of the Earth’s orbit. The Apollos: The orbits of these near-Earth asteroids cross the Earth’s orbit but have an orbital period of greater than one year. The Atens: These near-Earth asteroids have orbits that cross the Earth’s orbit but have an orbital period of less than one year. Asteroids are currently being monitored for their probability of colliding with the Earth. Such studies have predicted that asteroids may hit the Earth on February 1, 2019 and March 16, 2880. The probability of the 2880 collision is as high as 1 in 300. A number of projects in the field of astronomy, like Spacewatch, Near-Earth Asteroid Tracking and Catalina Sky Survey are being carried out to detect any threat of such catastrophes. Comets A comet is a small body in space. It was matter of great interest to astronomers like Sir Edmond Halley. Many decades later, comets still remain a challenging mystery for the field of astronomy. Space research institutes around the world have reported the existence of 3628 comets that are known and studied. Annually, an average of one comet is sighted by the naked eye from the surface of the Earth. According to the definitions given by the various space research organizations, a comet can be defined as a space body that travels in an elliptical orbit around the sun. Most of the comets travel in elliptical orbits. When the comet comes in the vicinity of the star it is orbiting around, its comma-like tail gets illuminated. A majority of comets are visible only through telescopes and other aids. There are however, some comets which are also visible to the naked eye. What is a Comet Made Up of? A comet is principally made up of ice, dust and different forms of gases. The nature of the components differs from comet to comet. The central part of a comet that looks like a ball is termed as the nucleus. The nucleus is principally made up of ice and frozen gases. The frozen components also include many other compounds like ammonia, methane and carbon dioxide. Rocks are another component of the nucleus. Due to such composition, the nucleus of the comet often resembles a huge ball of dirt and snow. It is also believed by some astronomers, that the nucleus of a comet is rather fragile because several comets have split into parts without any explainable reason except immense velocity. The huge elliptical orbit takes the comet in the range of heat of the star around which it is orbiting. When the comet enters the inner parts of the solar system, the frozen content of the nucleus starts melting. The gases and water within the nucleus vaporize as a result of radiation from the star and the solar wind. The immense velocity of the comet and the solar wind, push the vaporized matter away from the nucleus. This gives the comet it’s distinct tail and the comma-like appearance. The high amount of heat and the ions (charged particles that are formed due to the heat of the sun) cause the tail of the comet to glow. How are Comets Formed? According to their formation or birth, the comets can be classified into two types. The first type is short-term comets which originate in the Kuiper belt as space bodies beyond the orbit of Pluto. The gravitational pull of the planets in the solar system, causes the origin of short term comets. These comets enter the solar system and take the form of active and glowing comets. Long term comets originate as traveling bodies in the Oort cloud (located around 50,000 light years away from the sun). The gravitational attraction of the planets in the solar system and other gravitational forces cause these comets to form elliptical orbits. Death of a Comet The study of comets has revealed that they have a fragile structure. Sometimes, comets split into parts due to sheer velocity. The entry and exit of comets in the solar system in course of its orbit, reduces the amount of matter (ice and frozen gases) in it. Due to this reduction in matter, the comets break-up and disperse into clouds. A dead comet is nothing but an asteroid or a similar form of a space body. Sometimes the comets also crash in other planets when their orbits cross each other. The most famous example of such a comet is the Shoemaker Levy 9, that crashed into Jupiter. For astronomers who have spent their lives studying comets, it a very heart-breaking moment to gaze at a dying comet. The Halley’s Comet is said to be one of the most beautiful comets. Another very beautiful comet is the Hale-Bopp, that was discovered in the year 1995, on 23rd July. It was predicted by astronomers that the Halley’s Comet would be sighted in the November of 1835. Mark Twain, the famous writer, was born just two weeks after the sighting. He developed a very special liking towards the Halley’s Comet. In his biography he comments,†I came in with the Halley’s Comet, and expect to go with it. The Almighty has said no doubt, Now here are two unaccountable freaks; they came in together; they must go out together.† Halley’s Comet was next sighted on 20th April, 1910. Twain ended the journey of his life the very next day. The journey of any comet is indeed like that of Mark Twain. It is remarkably long, fast, adventurous as it streaks across the dark sky. Haley’s comet Historical Spottings British scientist, Edmond Halley who observed the comet in 1682, was the first person to establish its periodic reappearance after every 75-76 years. He studied the comet and quite accurately predicted that it had earlier appeared in 1531 and in 1607. It was named ‘Halley’ in his honor and was observed again in 1758 as stated by him. It was last seen in February 1986. However, this was not the first time the comet was in focus. The first sighting recorded, was way back in 240 BC, by the Chinese and was mentioned in a chronicle, ‘Records of the Great Historian’. The comet also finds a mention in a Babylonian clay inscription of 164 BC. It has always been a subject of great interest, since it was believed to have an influence on the contemporary events. Armenian king Tigranes II, had its image printed on the coins issued in his regime after it was sighted in 87 BC. Therefore, even though the recurrence of the comet was an unknown fact, people were fascinated b y its appearance. The bright star that appeared in the night sky in 12 BC, coinciding with the birth of Jesus, is widely believed to be the Halley’s comet. Giotto Di Bondone, the famous Italian painter, who lived before the renaissance era, painted it in his work ‘The Star of Bethlehem’ in the Nativity, in 1305. He had seen the comet appear in 1301 and was impressed by the spectacle. In the middle ages, the appearance of a comet was considered to be a warning sign of a forthcoming danger. The most famous incident of spotting a comet during this period, was in 1066, before the Battle of Hastings. King Harold who had lost the battle, was believed to have seen the comet due to which he was cursed. In fact, the Bayeux Tapestry in Normandy, France, signifies the Norman victory in this battle with an image of King Harold looking at the comet in the sky. In 1456, Pope Calixtus III had condemned its appearance considering it to be an evil omen. Three years prior to this, Europe was defeated by the Ottoman Empire. Human beings have always blamed celestial phenomena, whenever they have not been able to explain the causes of certain unfavorable events. Historically, the presence of a comet in the night sky was commonly cited as the reason behind difficult situations that were beyond the reasoning of common man. A French physician, Ambroise, had described the pitiful conditions of middle ages, when a comet was seen just before the spread of a big epidemic. According to him, some people were scared to death while others fell sick on seeing the comet. It was believed to be some ‘evil form’ leaving behind a trail of blood, believed to be a sign of misery. Recent Spottings In the 16th and the 17th century, scientists learned to calculate the speed and distance at which comets travel around the Sun. Once, Edmond Halley had established the year of its reappearance, Halley’s comet became a matter of great interest. Although, he didn’t live to see his prediction coming true, his observation had a significant impact on the way society perceived comets. The sighting of a comet, especially Halley’s comet became less of a concern and more of a curiosity among people. Once people realized that comets are orbiting bodies just like planets, they became less apprehensive on the arrival of a comet in the Earth’s visibility zone. The change in the attitude of the people was seen in the depiction of the comet in the contemporary pictures. Halley’s comet was a subject of scientific study and was depicted as a beautiful heavenly body in the sky. Famous American writer Mark Twain was born in 1835, the year when Halley’s comet ha d appeared. He predicted in 1909 that since he had ‘come’ with the comet he will ‘go out’ with it. Sure enough, he passed away a year after the comet reappeared in 1910. In the 1900s, it had appeared twice; once in 1910 and then in 1986. Further studies gave us a deep insight into the structure, composition and orbital journey of many different comets. Halley’s comet has one of the shortest orbital paths. It is classified as a short period comet, i.e. comets having an orbit period of 200 years or less. Once upon a time, it belonged to the long period class, but due to the gravitational force of planets, its orbit shortened over a period of time. Today, it is known that comets like ‘Hale Bopp’ which appeared in 1997, will reappear after 4200 years! Thus, Halley’s comet is the most frequently spotted one. Recently, it was seen in February 1986. During this visit, it was subjected to its biggest scrutiny ever. Five spacecrafts from The European Space Agency, Japan and the USSR were launched to study its surface. Structure and Composition of Halley’s Comet Halley’s comet is a big mass of ice and dust, having an elliptical orbit and shaped like a peanut. It has a highly elongated orbit, taking it very close to the Sun. It flings off far in the outer solar system, similar to a slingshot motion. The composition is mainly of water, sodium monoxide, methane, ammonia, hydrocarbons, iron and sodium. Its closest distance from the Sun was found to be just 0.6 AU (astronomical unit) and the farthest distance was calculated to be 35 AU, roughly the same distance as that of Pluto. It orbits the Sun in a retrograde or in the direction opposite to that of the planets’ revolution. The speed with respect to the Earth is quite high, since it is highly eccentric and inclined. The day time is relatively more on its surface and its maximum temperature rises up to 77 degrees celsius. Due to its large size and a well-defined and regular orbit, it was easy for the probe missions photograph it closely and study its surface. The mass of the comet is 1.7Ãâ€"1015 kilograms and the size of the nucleus has been estimated to be 15 km Ãâ€" 7 km Ãâ€" 7 km. Winds blowing near its surface are so strong that 1 gram particle of dust which hit the Giotto space probe, briefly destabilized it. Halley’s comet will next appear in 2062. Comets have always been a fascination for human beings and will continue to mesmerize generations to come, as we discover more interesting facts about these spectacular fireballs, the comets. Comet lullin Comet Lulin was discovered on July 11, 2007, by the duo of Ye Quanzhi and Lin Chi-Sheng. A non-periodic comet, Lulin appears to be greenish in color. This green color is attributed to the presence of gases such as cyanogen and diatomic carbon, which produce a green glow when illuminated by sunlight in the vacuum of the space. Officially designated as C/2007 N3 (Lulin), it is also known as the ‘Comet of Cooperation’ in China and Taiwan, as the two individuals involved in its discovery, were from these two countries. This comet was first photographed by Taiwanese astronomer Lin Chi-Sheng on July 11, 2007, while he was working on the Lulin Sky Survey Project (LUSS) at the Lulin observatory in Nantou, Taiwan. The Lulin Sky Survey Project aims to identify the numerous small objects in the solar system, particularly those that pose possible hazards to our planet. Lin used a 16-inch telescope to photograph this comet, which was initially assumed to be an asteroid. A few days later, Ye Quanzhi, a 19-year old student of meteorology from Sun Yat-Sen University, China, recognized this comet while going through Lin’s photographs. Its status of being a comet was confirmed after the presence of coma, the nebulous envelope around the nucleus of the comet, was noticed. Both, Lin and Quanzhi were accredited with the discovery of this new comet. As it was first noticed from the Lulin Observatory, it was named as Comet Lulin. Comet Lulin was seen in the Libra constellation from January to March 2009. In January, it was getting brighter and could be seen just before dawn; while in February, the brightness reached its peak. Eventually, in March, it started to fade as it went farther away from the Earth. While it was approaching the Earth, it had a typical tail pointing away from the Sun, as well as an ‘anti-tail’ which was directly pointing towards the sun. Although, it was assumed that this anti-tail was observed only in photographs, so me observers reported that it was visible even from a telescope in February 2009. According to Brian Marsden, an astronomer at Smithsonian Astrophysical Observatory, Massachusetts, this comet’s closest approach to the sun was on January 10, 2009 when it reached a distance of 113 million miles from the sun. He noticed that the comet was moving in a retrograde orbit that is near-parabolic. On February 24, Comet Lulin came the closest to the Earth, at a distance of 0.41 AU or 38 million miles to be precise. On February 4, 2009, a team of Italian astronomers, under the leadership of Ernesto Guido, witnessed a strange phenomenon taking place in comet Lulin. While photographing the comet with a remotely controlled telescope in New Mexico, they saw that its tail suddenly disconnected. Ernesto attributed this odd phenomenon to magnetic disturbance of the solar wind hitting the comet. Earlier, this had been observed with Comet Encke too, when coronal mass ejection occurred, due to such magnetic storms. Photographs taken by NASA’s Swift Gamma-ray Explorer satellite in ultra-violet and X-rays show that Lulin is shedding 800 gallons of water every second. Observations by NASA also revealed that the surface material of the comet was burning away due to sun’s heat. This sighting of Comet Lulin was a once-in-a-lifetime opportunity for the whole world, as there is no possibility of this comet returning to the inner solar system, at least not for the next thousand years. Human kind has always looked to the heavens in awe and wonder, and sometimes in fear. Perhaps no other astronomical phenomenon except a total solar eclipse has historically evoked as much fear as comets. When the specter of fear is removed, however, they emerge as strikingly beautiful objects in the sky. It was once believed that if earth passed through a tail of a comet, its inhabitants would die; this theory has been discredited. Comets are messengers from a time long past. Most are chunks of dirty ice, locked away in the Oort cloud for billions of years. (Oort cloud: – It is the source for long period comets, with orbital periods of greater than two hundred years.) Comets are familiar to nearly everyone as striking star like objects with long tails stretching across a wide band of the sky. The most famous comet, Halley’s comet makes its return to the skies every seventy-five years. The word â€Å"comet† is derived from a Greek word meaning â€Å"long haired† Comets were greatly feared before the twentieth century as bad omens. Since then, they have been identified and cataloged as objects that come from deep space. Most of them occupy orbits that carry them far outside the solar system. Many of them make only a single approach to the sun and never return again, while others exist in stable, but highly elliptical orbits that allow them to return after an extended period of time, su ch as the Halley’s comet. In 1986, the European space probe Giotto passed about 600 kilometers from the Comet Halley as it made its close approach to the sun. The probe verified existing theories that comets are made up of ices covered by black dust or soil. The spacecraft confirmed a theory that had been advanced prior to the reconnaissance that described comets as â€Å"dirty snowballs.† Using data taken by the spacecraft, scientists determined that the dust is composed of carbon, hydrogen, oxygen, and nitrogen. Other metals have also been discovered in comets, such as iron, calcium, nickel, potassium, copper and silicon. Halley’s comet was one of the darkest objects ever seen in the solar system; it was basically flat black. Comets are composed of a mixture of ices and dust. As a comet approaches the sun, it absorbs the suns energy and warms up. The main body of the comet is called the nucleus. As the nucleus warms, the ice beneath the comets soil evaporates. Because the comet has no atmosphere, the evaporated substance (also called a volatile) escapes into the vacuum of space as a gaseous envelope that surrounds the comet called â€Å"coma.† As the coma grows, it forms a plume of vapor that carries away some of the comets surface as well. This mixture of evaporated volatile particles and dust is carried away from the comet by solar wind, is ionized by high-energy particles, and creates the spectacular tail of the comet. The comet’s tail, glowing in the solar wind, can stream behind the comet for millions of kilometers. The nucleus of the comet consists of mostly volatile ices and dust. The ice is nearly all water ice, but there is also evidence of ices composed of carbon dioxide and methane. More elementary compounds of nitrogen, oxygen, and carbon monoxide may exist as volatile ices. Comets are typically small bodies (comparatively!!). Halley’s comet is a potato shaped object, 14 by 17 kilometers. The largest known comet is Chiron, which is estimated to be approximately 200 kilometers in diameter. Comets are thought to have formed as the solar system evolved. The material of which comets are composed was constructed by accretion at the outer edge of the disk of material that ultimately became the sun and planets. Because the comet material was fashioned at the outer edge of the solar system, the sun did not evaporate the volatiles in the cometary material. At the same time, the giant planets of the solar system formed at what would become the outer orbits of the solar system. These massive planets encountered the newly formed comets, and the ones that were not engulfed by the giant planets were, over the first billion years, catapulted into interstellar space by the planets massive gravitational fields. Not all comets met that fate, however. Some were gently nudged into stable orbits closer to the sun. Others were flung into the inner solar system and impacted the inner planets. Relevance: – The study of comets involves detailed knowledge of its composition of the outer regions of the solar system and the space between the last planet and 100,000 astronomical units onwards. Cometary study also seeks to understand complex gravitational interactions between bodies separated by wide distances and even gravitational interactions between tiny comets, their behavior when approaching the sun, and something of the makeup and evolution of the early solar system. New comets approaching the sun for the first time have been held in deep freeze in the Oort cloud and are thought to be composed of primordial material of the newly forming solar system. They have been tied up in the Oort cloud for billions of years at temperatures slightly above absolute zero. As they approach the sun, their internal gases begin to steam away. A detailed study of an approaching comet may tell cosmologists about the composition of the early solar systems. Comets and their approach have also hinted at the existence of the elusive brown dwarf, thought to be one of the most common bodies of interstellar space. Because they are so dim, they are all but invisible from Earth. On the other hand, because brown dwarfs are thought to be so plentiful, the study of comets and their orbits may give the first real clues to the former’s reality and abundance. In the early 1980s the existence of the galactic tidal action was merely speculation. Since then, careful study of cometary orbits and approaches has favorable supported the theory of galactic tides. In the close approach of Halley’s comet by an unmanned spacecraft in 1986, a wealth of information was recovered on the shape, behavior, and composition of comets. The existence of the Oort cloud and the concept gravitational interactions by passing objects in space have led to the theory of periodic comet showers. Such comet showers, separated by periods of tens of millions of years, may be responsible for the mass extinction on Earth. There is a wide speculation that Earth was struck by one or more comets 70 million years ago, which wiped out the dinosaurs. Some scientists have speculated that this extinction was the result of a shower of comets from the Oort cloud, sent on their close approach to the sun by a passing star or brown dwarf through the Oort cloud. Comets have been used to judge vast distances, evaluate the composition of the solar system as it was being born, and even test the idea that the gravity of the entire galaxy can make a difference to the smallest objects in space. Comets have been used as yardsticks to evaluate what may be the most type of star in the galaxy-the brown dwarf-which ironically is one that may never be seen. They have also been called dirty snowballs. Halley’s comet was so black that it was the darkest object ever seen in space. Yet, from these dirty specks of ice, cosmologists have witnessed some of the most spectacular light shows. Ultimately comets may also generate clues to some of the most fundamental secrets about the solar system and planets. From these tiny messengers, cosmologists may unlock and examine pristine elements from creation itself.