Oct. 28 – 2B03 28/10/2011 9:33:00 AM
Once you pass event horizon, you would have to accelerate to a speed
greater than c to escape.
Tidal forces (differential forces) – force on feet different than force on head –
Larger black holes – don’t necessarily get stretched
More dramatic w/ small black holes
Because of effects of TD and GR, you don’t see anything fall inside a black
But stuff does fall in
Last photons we see, infinitely time dilated
o Closer to event horizon, blows up to infinity
Black holes – small in astronomical scales
we never see anything close to the scale of the event horizon.
we see material close to the black hole -> many swarchild radii
really hot gas emits x ray radiation.
No light can escape the event horizon.
Systems with orbits – good place to look for black holes
If you see stars orbiting something, but cant see anything, it might
be a black hole, especially if its orbiting quite strongly.
If a black hole is close to the companion star, it is possible that it can strip
the outer layer of gas of the star. Good way to look for black holes.
Super-massive black holes
Something in the centre that has a lot of solar mass.
AMount of mass and volume -> gives us density.
How do you make big black holes in the centre of galaxies?
Merging smaller black holes. THey send out gravity waves - we should be able to detect them
Spirals into elipticals.
As 2 galaxies merge, they will orbit and lose energy in their orbit. If
you take 2 really dense objects, lose energy, and do something
with angular momentum.
Hawking radiation – black holes can lose mass and energy.
For all purposes, black holes GROW. Hawking radiation negligible.
LHC – possible that they are creating black holes (tiny though; short lived)
Particle collider -> theoretically possible to create them – very
quickly evaporate away.
Wormholes – something that is possible thr