PCS 581 Lecture Notes - Lecture 6: Ergosphere, Global Positioning System, Kerr Metric
Lecture 6: Black Holes
Pair Annihilation/Production
There are matter and antimatter and if they collide they annihilate
If you have enough energy in one spot
otwo gamma rays colliding can turn into protons (production)
omatter and antimatter colliding can produce gamma rays – light (annihilation)
Matter hitting matter will do neither
Annihilation creates light
Hawking Radiation
When production happens closer to the event horizon, one particle would fall in and
other come out – it will look like something is coming out of the black hole
The production of matter and antimatter near the black hole results in one particle
falling in while the other escapes – it looks like something is coming out of the black
hole
Evaporation
This means loss of energy (mass), and shrinking
oThe particle falling into the black hole is actually removing energy from the black
hole – Energy = mass and since its losing energy it is also losing mass – As it loses
energy it is losing mass
Small ones emit more, evaporate faster
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Whatever energy it is losing, it gains it back from eating CMB in empty space – space is
full of CMB
To emit more than it would absorb from the CMB, need to be less than mass of the
Moon
oA car-mass black hole evaporates in a nanosecond
oSmallest mass for a stellar black hole? Black hole starts at 3MSun
Primordial Mini Black Hole
Born during the super-dense early universe
oOr during rapid expansion and compression of inflation
oTheoretical, but might be found via Hawking radiation
Radius is a cm
Mass of Earth
During primordial early universe when there was so much stiff everywhere, they
collided and created black holes, or inflation caused it
oIt is possible that mini black holes formed in vast quantities in early universe and
resulted in a lot of hawking radiation
oCan’t look back because beyond our limit to see
The “Firewall”
Theory from 2010
Ingoing/outgoing particles are quantum entangled
There is a real science of transportation with two particles entangles in two locations
This relationship is broken when one falls into event horizon – and if the relationship is
shattered at event horizon – the event horizon would be on fire and release a lot of
energy
The event horizon would be a very deadly place
Hawking vs. the Firewall
2014: Stephen Hawking says that the event horizon, as we know, can’t exist
oBlack holes / event horizon are there its just we don’t know the environment
around it and we can’t figure out our math – we don’t know and we don’t
understand
oWhoever figures it out will be the next Einstein
Some energy and information might escape…
Warping Space and Time
Gravity According to Newton
Gravity is the result of two factors: Action at a distance
What connects these two objects? Force between two objects – attraction
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Gravity According to Einstein
Einstein showed that what we perceive as gravity arises from curvature of spacetime
oBritish were pissed, some German guy comes around and throws away English
theory – Another English guy proved it right
oGravity is the bending/warping of space time by a massive object
oMassive objects on a rubber sheet will warp the surface – things moving around
on that sheet, their path will bend
Matter distorts spacetime in a manner analogous to how heavy weights distorts a
rubber sheet
Newton says pulled by the Sun, Einstein says comet turns because of that bend in the
path created by warp in space time by the Sun – this is complicated math and newton’s
theory is simple and clean that’s why taught in school
oThings will move around in a curved surface
oIt is not about a force between two objects, but that warp in space time by a
massive object
Orbiting Curved Space Time
No friction in space so everything stays and orbits in place instead of spiraling in (which
requires friction)
Earth creates own indentation
Sun will move a little bit because of the curvature of the earth but not so much
Near a black hole Einstein’s black theory works
Another thing it works best for is mercury’s orbit – does a precision – not a perfect circle
– as mercury precise we can’t figure it out with newtons theory – worked with Einstein’s
theory
General relativity is more accurate than newtons law
Gravitational Lensing
Lensing is not predicted by newtons law
If light is moving through space, if it moves through curved space, light will bend too
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Document Summary
There are matter and antimatter and if they collide they annihilate. If you have enough energy in one spot: two gamma rays colliding can turn into protons (production, matter and antimatter colliding can produce gamma rays light (annihilation) When production happens closer to the event horizon, one particle would fall in and other come out it will look like something is coming out of the black hole. The production of matter and antimatter near the black hole results in one particle falling in while the other escapes it looks like something is coming out of the black hole. Whatever energy it is losing, it gains it back from eating cmb in empty space space is full of cmb. To emit more than it would absorb from the cmb, need to be less than mass of the. Born during the super-dense early universe: or during rapid expansion and compression of inflation, theoretical, but might be found via hawking radiation.
