# Black Holes Research and Report

Chris Baynes        Research and Report        A2 Physics

Contents

Page number

3                What is a Black Hole?

Black Hole anatomy

4                Types of Black Hole

6                 Mass of a black hole

8                What happens when Black Holes Collide?

Gravitational lensing

10                Einstein rings

Evaluation

11                References

Black Holes

By doing this assignment I aim to gain a better understanding of the physics behind

Black Holes

What is a Black Hole?

To understand a black hole, you must first have an understanding of gravity in space. Imagine yourself on a trampoline; you make an indentation in the trampoline fabric. If someone was to roll a ball past you on the trampoline, it would begin to spiral towards you, down into the indent you have made. This is very similar to the way gravity works in space and time. The ‘fabric of spacetime’ is an imaginary mesh running through space (see right) which can be deformed and warped by the gravity of stars and planets. This is the principle upon which black holes work.

A black hole essentially is an incredibly compact body which has warped space-time enough to make any escape from the force of gravity impossible. They are thought to be at the centre of galaxies, including our own Milky Way. As the name implies, a blackhole cannot emit or reflect any light; making them practically invisible. If enough mass is concentrated into a small enough region, the curvature of space-time becomes so harsh that nothing can continue to orbit stably; not even light. The ultimate fate of all incoming matter is to be destroyed in a singularity, a region of infinite density. The interior of a black hole is poorly understood because no form of information can ever leave. However new technologies are allowing us to receive a new phenomenon called hawking radiation, so this may be true for only a short period of time.

Black holes are formed by the gravitational collapse of a star, in which the pressure created by the core of the star becomes insufficient to resist its own gravity. This causes the star to collapse in on itself, known as a supernova. If the star was of large enough mass (at least 10 times the mass of the sun, depending on the type of black hole), it will collapse to form a black hole.

Black hole ‘anatomy’

• Singularity-lies at the centre of the black hole, where matter is crushed to infinite density. This means the mass of the black hole is compressed into an area with 0 volume.
• Ergosphere-a region located outside a rotating black hole. It drags spacetime around with it at a speed exceeding that of light.
• Event horizon-the boundary in spacetime. Due to the massive gravitational pull, an extremely strong deformation occurs in spacetime. This means that of all the possible paths a particle could take, none lead away from the singularity (see
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#### Here's what a star student thought of this essay

The quality of writing in this report is of a high standard, the candidate uses a good range of vocabulary, they use appropriate scientific terms and clearly show a very good understanding of physics. In addition this there are no issues with punctuation or grammar and only one or two spelling/typing errors.

The candidate has provided a table of contents which is often a good idea when you have many different topics to cover. This makes it clear to the reader which topics you plan to discuss. Furthermore the candidate has clearly taken the time to undergo independent research as they discuss complex theories relating to black holes. Sensibly they have also provided a list of resources they have used. It is always a good idea to state any sources you use when researching a topic. Finally the candidates conclusion could be improved. Though they give an evaluation and include a personal response, it is a little too brief. A good conclusion should summarise the key points you have discussed and state why these are important as this helps to draw the essay to a close.

The candidate gives a very in depth account and their report is interesting and easy to follow. An example of this is in the first paragraph, where the candidate uses a real life situation to explain the concept of a black hole, this engages the reader and helps explain the topic to someone with a lesser understanding of physics. When you introduce a scientific concept it is a very good idea to make it as simple as possible and define key terms and ideas before discussing the main points. As well as demonstrating your understanding this makes your work accessible to a wider audience.