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Black Holes

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Introduction

Research & Report Black Holes Contents Introduction 3 What is a Black hole? 4 Formation of Black Holes 4 Features of Black Holes 6 Discovering Black Holes 8 Where are they? 9 What would happen if an object falls into a black hole? 9 Theory of general relativity 10 Hawking Radiation 11 Evaluation & Conclusion 12 Bibliography/Reference 13 Appendix 14 Introduction For my research and report coursework topic I chose black hole as I've done a research on black holes for a presentation in the past so it would be fairly straightforward to do, and my current knowledge about black holes would help me to complete this coursework a lot easier. Moreover, I was always interested in astronomy, which includes black holes therefore doing a research and report coursework would enable me to expand ideas and knowledge. The fact that people are able to observe and analyse black holes in the boundless space also stimulated me to choose this topic because I was always curious about how people can analyse when black holes are millions of light-years away from where we live and unable to see. Also I wish to find out more about why there are so many theories associated with black holes and how the astronomers ended up making theories of their own, which are different to each other. I will be doing my researches on different areas of black holes. Firstly, I will find out how black holes were created in the first place, what they are consisted of and the size plus number of black holes in the universe, which will allow me to make a good start with basic explanations about black holes. Then I'll do some calculations for escape velocity to prove that the light cannot escape the black holes and make this coursework more reliable. Secondly, I will push this topic into more complicated areas of physics by bringing up the effect of black holes, ways of analysing and discovering black holes when even lights cannot escape because surely if light don't exist near the black holes they wouldn't be observable. ...read more.

Middle

The reason why the radius and mass are proportional is because G and c are constant therefore in the new equation an increase in m would cause r to increase too. So I thought it would be interesting to measure the Schwarzschild radius of Earth. In other words, how small does it have to be in order to turn into a black hole? G is (6.67 x 10-11), m is (5.9 x 1024) kg and c is (3 x 108) ms-1. If I put these into the equation I get (8.745 x 10-3) m, if I convert metres into millimetres and round up I get about 9mm of Schwarzschild radius. Therefore, the size required for the Earth to become a black hole is the radius of 9mm. Discovering Black Holes So how do we know whether black holes exist or not when Einstein's theory of general relativity proposes that the most densest and massive objects conceivable, such as black holes, have gravity that is so strong that nothing, not even light, can escape? Also even if we could know that they exist, how do we find out? As I explained earlier, massive amount of heat containing x-rays are generated from the pressure and friction within the accretion disks that surround black holes. These emitted x-rays are then picked up by the x-ray telescopes that orbit around just outside the Earth's atmosphere. This is one of the methods that astronomers use in order to detect and analyse black holes. The other method to detect black holes is called gravity lensing. It occurs when a massive object such as a black hole, passes between a star and the Earth. The black hole acts as a lens when its gravity bends the star's light rays and focuses them on the Earth. From an observer's view on the Earth, the star would appear to brighten and this is shown on the following diagram. ...read more.

Conclusion

In other words, I think an astronaut wouldn't necessarily be stretched because he is not big enough. Furthermore, it was hard writing this report because there were time and word limits to write a topic that is full of theories with very broad ideas, and for this reason I had to move on without any question or including my own ideas. Also some predictions would be easy to follow but never be able to understand in depth in terms of how the astronomer developed his idea or why it is believable. In addition, there were uncertainties about the description of the singularity for black holes because quantum mechanics is as well supported as general relativity and it does not allow objects to have zero size. But even though there isn't any well supported theory that combines these two, I decided to follow on general relativity because general relativity is a bigger scale theory that most articles follow. Apart from these problems I found everything else was fairly straightforward. On the other hand, there were several alternative ideas associated with black holes without the existence of singularity proposed such as the Gravastar, but they were thought to be artificial and no observable differences from black holes, and therefore denied. There were also a number of ideas based on quantum mechanics that black holes do not exist but are dark energy stars instead, again they were denied with little support. I already had basic ideas of black holes beforehand but after all the research and reading, I gained a lot more knowledge without myself realising. Moreover, I was pleased to have choice in choosing my own title to produce research and report, which I thought was good because I worked more enthusiastically than what I normally do. Although some people might think this is completely needless knowledge in our lives, but personally I felt doing this research and report coursework was beneficial because at some point in the future we will be expanding our ways into space. ...read more.

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