Black Hole

1. Black Hole Vacuum Cleaner of the Universe

2. Formation of Black Hole • nuclear fusion - tends to blow the star's hydrogen outward from the star's center • gravitation - tends to pull all hydrogen back in the direction it had come

3. Formation of Black Hole

4. Formation of Black Hole • primordial black hole is formed upon extreme compression of matter by external forces • One possibility of the existence of such black holes are during the early stages of the universe where high temperatures and pressures existed

5. Structure of Black Hole (1) • Schwarzschild singularity: a point of infinite density • Event horizon: boundary of the region inside which light cannot escape • Schwarzschild radius: radius of the event horizon Schwarzschild black hole (史瓦西黑洞)– a non-rotating black hole

6. Photon sphere

7. Structure of Black Hole (2) • Outer event horizon: Boundary inside of which nothing can resist being dragged around with the rotating mass • Inner event horizon: Boundary inside of which nothing can escape • Ergosphere: A particle entering it will be split into two: one falls into the black hole, and the other ejected with more energy Kerr black hole – a rotating black hole

8. Structure of Black Hole (2)

9. Evaporation • energy is "borrowed" from the vacuum, creating a particle - antiparticle pair • One particle of the pair is pulled into the black hole, and the other escapes, carrying with it some energy • A black hole of 1 solar mass would take ~ 10^66 years to evaporate completely

10. Curvature of space-time • A small celestial body with large mass • Severe curvature of space-time • Not even light can get out (light loses all energy in climbing out of such holes)

12. Detection of Black hole If light is not given off by black holes, how do we detect them?

13. Orbiting around nothing • When a star changes into a black hole, the strength of its gravitational field remains the same • The planets in orbit would continue in their orbits as usual • The planets would appear to be orbiting around nothing

14. X-ray telescope • The dust particles near the black hole speed and heat up, emitting x-rays • Objects that emit x-rays can be detected by x-ray telescopes outside of the Earth's atmosphere

15. Gravity-lensing • Gravity lensing occurs when a massive object passes between a star and the Earth. • From an observer's point of view on the Earth, the star would appear to brighten

16. Measuring mass • If a region has large amounts of dark mass, one can suspect the presence of a black hole

17. Falling into the black hole (Observing outside event horizon) • Time dilation • Gravitational redshift

18. Falling into the black hole (Observing inside event horizon)

19. Wormhole • Developed by Albert Einstein and Nathan Rosen in 1935 • Einstein-Rosen bridge • A shortcut between two points in space • Connecting a black hole and a white hole

21. E=mc^2

22. Wormhole • Exotic matter is required to keep a wormhole opened • Exotic matter has –ve mass and energy • Gravitationally repulsive

23. Light rays passed through a wormhole are defocused

24. Faster-than-light travel • Special relativity says that one cannot outrun a light signal in a fair race • It might be possible to beat a light signal by taking a different route

26. The Twin Paradox • A person who leaves Earth in a spaceship, travels at near light speed and returns will have aged less than someone who remains on Earth • http://webphysics.davidson.edu/physletprob/ch10_modern/twin.html

27. Time travel • If the traveler manages to outrun a light ray, perhaps by taking a shortcut through a wormhole or a warp bubble, he may return before he left

28. Grandfather Paradox • What happens if I go back in time and kill my grandfather, thus preventing my future existence? 

29. Thank You