2. A huge great enormous thing,
like — like nothing. A huge big
— well, like a — I don’t know —
like an enormous big nothing ...
Piglet describes the Heffalump,
in Winnie the Pooh by A.A. Milne
3. HHuuggee GGrraavviittyy
• Black Holes are Gravity Centers of The
Universe
• Size ~ 0 and Density ~ a
• Two Types
– Static
• Karl Schwarzschild solutions
– Rotating
• Kerr solutions
4. CChhaannddrraasseekkhhaarr LLiimmiitt
• Death of Star
• Red Giant
• White Dwarfs
– Mass of star<1.4 Solar mass
– Electron Degeneracy Pressure
• Neutron Stars
– 1.4 solar mass<Mass of star<3.0 solar mass
– Neutron Degeneracy Pressure
• Black Holes
– Mass of star >3.0 Solar mass
5. TThhee TTrraannssiittiioonn
• Pauli Exclusion Principle:
No two electrons can occupy the same position in space
• Electron Degeneracy Pressure :- Electrons are packed
side by side in a white dwarf This prevents it from
collapsing any further
• Neutron Degeneracy Pressure : - Neutrons are packed
side by side in a Neutron Star This prevents it from
collapsing any further
• More Mass More Gravity :- Nothing can stop Collision
• -> Black Holes
6. EEvveenntt HHoorriizzoonn
• Area around Black Hole,
from where nothing can be
escaped to outside
• Inside event horizon escape
velocity is greater than
speed of light.
John Wheeler
7. SScchhwwaarrzzsscchhiilldd RRaaddiiuuss
Karl Schwarzschild
(1876-1916)
• Distance from
singularity to event
horizon is called
Schwarzschild radius
• Schwarzschild radius is
a measure of the size of
black hole
11. Singularity Theorem
• Every black hole must have a singularity
inside itself
• There is no existence of a naked
singularly in the universe
12. Naked Singularity
Roger Penrose
(b1931)
A singularity that is not inside a black
hole (not
surrounded by an event horizon), and
therefore
can be seen by someone outside it
22. First Law
• If a body with a fixed mass and angular
momentum is fall into a black hole then
the mass and angular momentum of the
black hole increases that much.
• Resembles with the First law of
thermodynamics
• Energy conservation theorem
23. Second Law
• The surface area of a black hole is not
reduced in any process
• If two black holes combined then the
resultant surface area is greater than the
sum of surface areas of each black
holes.
• Surface area ->Entropy
• We cannot reduce the entropy of a
system.
24. Third Law
• The surface gravity of a black hole is
never become zero.
• Resumbles to third law in
thermodynamics
• We cannot reduce the temp: to absolute
zero.
25. Virtual Particles
•In quantum theory, there is an intrinsic uncertainty
in energy and time: DE Dt ≥ h/4p
•This implies the existence of ‘virtual particles’
even in a vacuum
•Virtual particles appear in pairs, consisting of a
particle and its corres-ponding antiparticle
26. Hawking Radiation
Stephen W. Hawking
(b1942)
• One partner of a virtual-particle
pair could fall into a black hole,
carrying negative energy with it
• Effectively, the black hole appears
to be emitting particles and losing
mass!
27. But this effect is very tiny
for normal black holes
• For a solar mass black hole
– Temperature = 10-7 K
– Lifetime = 1067 years
(age of universe = 1010 years)
• Since T µ 1/M, this effect is more
pronounced for small black holes
• Mini black holes created during
the Big Bang?
34. Expanding Universe
• Gravitational Field Equations
Expanding universe
" l Steady Universe
• Edwin Hubble and Milton
Heumanson (Mount Wilson
Observery)
• Expanding Universe
• Red Shift
Edwin Hubble
35. Freedman-Robertson-
Walker Model • Critical Mass
• Closed Universe
– Mu <Critical Mass
– Universe started Contracting after a particular time
• Flat Universe
– Mu = Critical Mass
– Expansion rate of universe become constant
• Open Universe
– Mu > Critical Mass
– Expansion rate increases with time
37. Big Bang Theory
• Lemaither and Gamove
• Universe Formed from a Big Bang
• Singularity is Big Bang Singularity
• The total universe formed from
that. Lemaither
George Gamow
40. Big Bang Theory Proofs
• Background Radiation
• Large Scale of universe
• Distribution of Galaxies
41. Other Theories
• Stedy State Theory
• Inflation Theory
• Big Crunch Theory
• Oscillatory state Theory
42. Will the Universe
Recollapse?
• Gravitational pull of the galaxies on each other
is slowing down the rate of expansion
• Required density for the universe to
recollapse is 4.5 x 10-30 g/cm3
• Observed density of luminous material
(stars, galaxies) is about 3 x 10-31 g/cm3
43. Dark Matter
• But there may be about 10
times this amount
in the form of ‘dark matter’
• So the universe is very
close to the threshold
for recollapse!
Measurements of the velocities of stars in
a galaxy show that there must be more
matter in the galaxy than is apparent.
This ‘dark matter’ is known to form an
invisible halo around the galaxy
44. Gravitational Waves
• The Variations in space-time (When
body Accelerated) causes
Gravitational Waves.
• Speed of Wave = C
• Large gravity related Phenomena
• Supernova, Black Holes etc…
45. Gravitational Wave Detector
• When GW passing through a body it
will expands the body in that
direction and contracts in opposite
direction by measuring this we can
detect GW.
46. LIGO
• The Laser Interferometer
Gravitational-Wave
Observatory Caltech.
50. Unification of the Four Forces
• Electricity + Magnetism
= Electromagnetism
• Electromagnetism + Weak
= Electroweak
• Electroweak + Strong
= Grand Unified Theory
(GUT)
• GUT + Gravity
= Theory of Everything
(TOE)??
51. Gravity
• Due to geometry rather than exchange of
particles
• Remains impossible to incorporate within
the framework of quantum field theory
like the other forces
52. Quantum Gravity?
• Does space-time fluctuate in
a quantum fashion at very
small scales?
• Called space-time foam
• How to describe this
mathematically?
53. Superstring Theory
• Best candidate for a TOE is superstring theory
• Assumes all fundamental
particles are actually
string-like objects rather
than point-like objects
• Different particles correspond to different
vibrational modes of the same string
55. Extra Dimensions?
• Superstring theory
predicts that space-time
is 10-dimensional (9 space + 1
time)
• The extra 6 dimensions
are thought to
be rolled up to a very
small size
56. Unsolved Problems
• Why Gravity happens?
• No – Graviton in Standard Model
• Dark Mater