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# Black holes (2)

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### Transcript

• 1. Black Holes Presented by- Jyotsana Sharma Btech (hons.) CSE RA1803A10
• 2. Black Holes Contents---
• History.
• Formation of black holes.
• Gravity deforms space time.
• Gravity bends path of light.
• Event horizon
• Falling into black holes.
• Rotating black holes.
• Techniques
• References
• 3. History-- The idea of preventing light from escaping as described by general theory of relativity was given by John Michelle. Even the British astronomer Pierre -Simon Laplace came with the same conclusion.
• 4. The intense gravitational field left when a giant star collapses. It is called a black hole because not even light can escape. Objects too heavy to be neutron stars collapse to black holes. Formation-
• 5. Formation Continued… As the mass increases, so does the gravitational pull. If the gravitational pull is such that even light can escape , then a black hole is formed.
• 6. Gravity deforms space time Diagrammatical representation
• 7. Gravity bends the path of light
• 8. Event horizon The point at which no light can escape.
• 9. A nonrotating black hole has only a “center” and a “surface”.
• The black hole is surrounded by an event horizon which is the sphere from which light cannot escape
• The distance between the black hole and its event horizon is the Schwarzschild radius (R Sch = 2GM/c 2 )
• The center of the black hole is a point of infinite density and zero volume, called a singularity
• 10. Falling into a black hole Falling into a black hole gravitational tidal forces pull spacetime in such a way that time becomes infinitely long (as viewed by distant observer). The falling observer sees ordinary free fall in a finite time.
• 11. Falling into a black hole
• Signals sent from the freely falling observer would be time dilated and red shifted.
• Once inside the event horizon, no communication with the universe outside the event horizon is possible.
• But incoming signals from external world can enter.
• A black hole of mass M has exactly the same gravitational field as an ordinary mass M at large distances.
• 12. Seeing black holes
• 13. Rotating black holes
• A rotating black hole (one with angular momentum) has an ergo sphere around the outside of the event horizon
• In the ergo sphere, space and time themselves are dragged along with the rotation of the black hole
• 14. 1-Accertion disks and gas jets. 2-Strong Radiation emissions 3-Gravitational lensing Techniques for finding black holes
• 15. Types of Black Holes-- 1-Supermassive Black holes. 2-Stellar- mass black holes. 3-Intermediate mass black holes.
• 16. Advantages and Disadvantages-- They can be significant in this way: 1-Individual modes may dominate the time evolution of some perturbation, and a whole set of them could be used to completely describe this time evolution. The disadvantages are that – 1-when a black hole evaporates information is really gone. 2-Due to this there is trouble in energy conservation. 3-Invariance in time predictability.
• 17. References--- 1-www.google.com. 2-www.wikipedia.com. 3-Anatony on Black holes.
• 18. THANK YOU ANY QUESTIONS???? ???