2. Introduction:
When the word “PHYSICS” be pronounced, suddenly two
names were strikes on our Mind they are
Sir Isaac Newton
and
Albert Einstein
3. Why???????????
Because they made great impact on the field physics
Newton is famous for his Gravitional laws
Einstein is famous for his Relativity theories
These two are unnegligible in physics
5. How………………………….?
Sir Isaac Newton
Universal Law of
Gravitation
Any two bodies in the
Universe attract each
other with a force
proportional to the
masses and inverse of
the square of the
separation, along the
line joining them.
F = Gm1m2/r2
6. Sir Isaac Newton could describe
gravity but couldn’t explain it.
– For 200 years, science didn’t have
an explanation for gravity until a
clerk in a patent office in
Switzerland named Albert Einstein…
7. Some defects!
By the beginning of the 20th century, Newton's law of
universal gravitation had been accepted for more than
two hundred years as a valid description of the
gravitational force between masses.
In Newton's model, gravity is the result of an attractive
force between massive objects.
Although even Newton was troubled by the unknown
nature of that force, the basic framework was
extremely successful at describing motion.
8. Einstein.,,,,,
Albert Einstein was a German-
born theoretical physicist
He developed the general
theory of relativity,
It is one of the two pillars of
modern physics
9. Cont…….,,
Einstein's work is also known for its influence on the
philosophy of science
Einstein is best known in popular culture for his mass–
energy equivalence formula E = mc2
Introduced his Special Theory of Relativity in 1905 and
His General Theory of Relativity in 1915.
10. <Corrections>
The first showed that Newton's Three Laws of Motion
were only approximately correct, breaking down when
velocities approached that of light.
The second showed that Newton's Law of Gravitation
was also only approximately correct, breaking down
when gravitation becames very strong.
12. Special Theory of Relativity
Special theory was proposed on 1905
It is for non accelerated reference frame
A Reference Frame is the point of View, from which we Observe
an Object.
A Reference Frame is the Observer it self, as the Velocity and
acceleration are common in Both.
13. Postulates of Special Theory of
Relativity*
“The Laws of physics are same in all
Inertial Frame of reference”
“The Speed of Light in free space has
the same value in all Inertial Frames.”
14. The Major Consequences To This Theory are:-
Length Contraction
Mass Expansion
Time Dilation
15. Length Contraction
“It is the phenomenon of Shortening of Length which is in
the relative motion with respect to the observer”
Thus the length of a body appearing to an observer depends
upon the relative velocity of the body with respect to the
Observer.
It is given by l = lo /(1-v 2
/c 2
) 0.5
16. Mass Expansion , E = mc2
As an object's speed approaches the speed of light from
an observer's point of view, its relativistic mass
increases thereby making it more and more difficult to
accelerate it from within the observer's frame of
reference.
The energy content of an object at rest with mass m
equals mc2
. Conservation of energy implies that, in any
reaction, a decrease of the sum of the masses of
particles must be accompanied by an increase in kinetic
energies of the particles after the reaction. Similarly,
the mass of an object can be increased by taking in
kinetic energies.
E = mc2
17. Time Dilation
Time Dilation is the phenomenon of slowing down of
a clock , as determined by an observer who is in
relative motion with the Clock.” **
As it is an relative thus the Extent of Dilation
depends upon
the Relative Velocity of the clock w.r.t. the
observer.
It is an very important consequence of the Special
Theory of Relativity .And is given by t = to/(1-v 2
/c
2
) 0.5
18. General theory of Relativity
General relativity is a theory of gravitation that was
developed by
Albert Einstein between 1907 and 1915.
According to general relativity, the observed
gravitational effect between masses resultsfrom their
warping of spacetime.
19. Facts…………………
General Relativity, or GR, was created in order to better
understand gravity
It has helped us to answer why gravity exists
General Relativity has many predictions most of which
have been verified by experiment with amazing
accuracy
20. Facts…………..,
The special theory of relativity encompasses inertial
frames of reference moving at uniform relative
velocities
Einstein asked whether or not systems moving in
nonuniform motion with respect to one another could
be relative and came up with the idea of general
relativity
21. The History of GR
Developed between 1907 and 1915
The beginnings of GR germinate in 1907 with Einstein’s
thought experiment concerning a free-falling observer that he
called the happiest thought of his life: "For an observer
falling freely from the roof of a house, the
gravitational field does not exist"
22. The History of GR
1907- published first paper applying SR to accelerating
reference frames that also predicted gravitational time dilation
1911- published paper predicting gravitational lensing
1912- Einstein was focused on formulating a theory of
spacetime that was purely geometrical
23. The History of GR
By 1915 Einstein had developed what are known as the
Einstein Field Equations
General Theory of Relativity published in Annalen der Physik
in 1916
24. Basic concepts
General relativity is the extension of special relativity.
It includes the effects of accelerating objects and their
mass on spacetime.
As a result, the theory is an explanation of gravity.
It is based on two concepts: (1) the principle of
equivalence, which is an extension of Einstein’s first
postulate of special relativity and (2) the curvature of
spacetime due to gravity.
25. Principle of Equivalence
The principle of
equivalence is an
experiment in
noninertial reference
frames.
Consider an astronaut
sitting in a confined
space on a rocket
placed on Earth. The
astronaut is strapped
into a chair that is
mounted on a weighing
scale that indicates a
mass M. The astronaut
drops a safety manual
that falls to the floor.
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26. Cont…………….
Now contrast this situation with the rocket accelerating
through space. The gravitational force of the Earth is
now negligible. If the acceleration has exactly the same
magnitude g on Earth, then the weighing scale indicates
the same mass M that it did on Earth, and the safety
manual still falls with the same acceleration as
measured by the astronaut. The question is: How can
the astronaut tell whether the rocket is on earth or in
space?
Principle of equivalence: There is no experiment that
can be done in a small confined space that can detect
the difference between a uniform gravitational field
and an equivalent uniform acceleration.
27. Spacetime Curvature of Space
Light bending for the Earth observer seems to violate the premise
that the velocity of light is constant from special relativity. Light
traveling at a constant velocity implies that it travels in a straight
line.
Einstein recognized that we need to expand our definition of a
straight line.
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28. Cont………………………………..
The shortest distance between two points on a flat
surface appears different than the same distance
between points on a sphere. The path on the sphere
appears curved. We shall expand our definition of a
straight line to include any minimized distance
between two points.
Thus if the spacetime near the Earth is not flat, then
the straight line path of light near the Earth will appear
curved.
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29. Einstein's geometric gravity
In Einstein's theory of
general relativity, gravity is a
distortion of space-time.
Particles follow the straightest
possible paths in that space-time. But because
space-time is now distorted, even on those
straightest paths, particles accelerate as if they
were under the influence of what Newton called
the gravitational force.
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30. Consequence of general theory
Gravitational time dilation
gravitational time delay
Gravitational waves
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31. Gravitational time dilation
Assuming that the equivalence principle holds,
gravity influences the passage of time
Light sent down into a gravity well is
blueshifted,whereas light sent in the opposite
direction is redshifted; collectively, these two
effects are known as the gravitational frequency
shift.
More generally, processes close to a massive body
run more slowly when compared with processes
taking place farther away; this effect is known as
gravitational time dilation
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32. gravitational time delay
General relativity predicts that
the path of light is bent in a
gravitational field;
light passing a massive body is
deflected towards that body. This
effect has been confirmed by
observing the light of stars or
distant quasars being deflected as
it passes the Sun
gravitational time delay (or
Shapiro delay), the phenomenon
that light signals
take longer to move through a
gravitational field than they
would in the absence of that field
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33. Gravitational Waves
Fluctuation of spacetime curvature that is propagated as a
wave
Radiates away from accelerating bodies
Carries energy away from source
Predicts that two massive bodies rotating about their
center of mass will loose energy in the form of gravity
waves and the orbit will decay
34. Tests of General Relativity
Bending of Light
During a solar eclipse of the sun by the moon,
most of the sun’s light is blocked on Earth,
which afforded the opportunity to view
starlight passing close to the sun in 1919. The
starlight was bent as it passed near the sun
which caused the star to appear displaced.
Einstein’s general theory predicted a
deflection of 1.75 seconds of arc, and the
two measurements found 1.98 ± 0.16 and
1.61 ± 0.40 seconds.
Since the eclipse of 1919, many experiments,
using both starlight and radio waves from
quasars, have confirmed Einstein’s
predictions about the bending of light with
increasingly good accuracy.
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36. Gravitational Lensing
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When light from a
distant object like a
quasar passes by a
nearby galaxy on its
way to us on Earth, the
light can be bent
multiple times as it
passes in different
directions around the
galaxy.
37. Perihelion Shift of Mercury
The orbits of the planets are ellipses, and the point closest to the
sun in a planetary orbit is called the perihelion. It has been known
for hundreds of years that Mercury’s orbit precesses about the sun.
Accounting for the perturbations of the other planets left 43
seconds of arc per century that was previously unexplained by
classical physics.
The curvature of spacetime explained by general relativity
accounted for the 43 seconds of arc shift in the orbit of Mercury.
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38. Gravitational Wave Experiments
Taylor and Hulse discovered a binary system of two neutron stars
that lose energy due to gravitational waves that agrees with the
predictions of general relativity.
LIGO is a large Michelson interferometer device that uses four test
masses on two arms of the interferometer. The device will detect
changes in length of the arms due to a passing wave.
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NASA and the European Space
Agency (ESA) are jointly
developing a space-based probe
called the Laser Interferometer
Space Antenna (LISA) which will
measure fluctuations in its
triangular shape.
39. Black Holes
Black Holes are the most profound prediction of general
relativity
A black hole is a large body of matter that is so dense
that nothing can escape its gravitational attraction, at a
given distance, known as the Schwarzschild radius
40. Black Holes
Do they exist? FOR SURE!
Black Holes come in two different sizes: Stellar (5 to 20
solar masses) and supermassive (millions or billions of
times the mass of the sun)
Black Holes are detected by either their gravitational
influence on nearby bodies or through electromagnetic
radiation
41. Further Implications of GR
Cosmology-the ultimate fate of the universe
The Hawking Effect-the first combination of the
quantum theory with general relativity
42. Conclusion
What have we learned from general relativity?
What can we predict using GR?
GR is one of the most accurate physical theories to date
43. Time travel used to be thought of as just
science fiction, but Einstein's general
theory of relativity allows for the
possibility that we could warp space-time
so much that you could go off in a rocket
and return before you set out.
-(Stephen Hawking)
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