Black Hole Vacuum Cleaner of the Universe

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

Mass of Star Outcome < 1.4 solar mass White Dwarf > 1.4 solar mass & < 3.0 solar mass Neutron Star > 3.0 solar mass Black Hole Formation of Black Hole

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

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

Photon sphere

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 Structure of Black Hole (2) Kerr black hole – a rotating black hole

Structure of Black Hole (2)

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

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)

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

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

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

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

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

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

Falling into the black hole (Observing inside event horizon)

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

E=mc^2

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

Light rays passed through a wormhole are defocused

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

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 b/ch10_modern/twin.html b/ch10_modern/twin.html

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

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

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