EINSTEIN’S THEORIES OF RELATIVITY

Dizon, Samantah LouiseLacanilao, Alezandria NicoleMembrere, Ingrid MaeHipolito, Yza Lennor

Special Theory of Relativity It was published in 1905. It deals with problems involving

inertial frames of reference (frames moving at constant velocity) with respect to each other.

General Theory of Relativity It was published in 1915. It deals with problems involving

accelerated reference frames.

The Search for the Ether: The Michelson-Morley Experiment

What is Ether?

It was believed to occupy all cosmos. It is undetectable by ordinary means. It was supposed to permeate all matter and

space. It was supposedly a medium to act as a

carrier of waves, including light.

The Michelson Interferometer

(c)RiA

Results of the Experiment

The results were negative, even after repeating it six years later.

The ether was not stationary but was dragged along with the earth.

The earth was fixed in the ether and everything else in the universe moved with respect to the earth and the ether.

The velocity of light was always at constant with respect to the source which emitted it.

Ether did not exist at all.

Hypotheses for the Results

Postulates of Special Theory of Relativity

Postulate 1: The speed of light is independent of the motion of the Light of source or receiver. This postulate concerns the constancy of

the speed of light to all observers. All measurements, whether stationary or

moving observers relative to a moving or stationary source always give the same value for the speed of light, c=3x10 m/s.

This postulated is supported by the results of the Michelson-Morley Experiments.

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Postulate 2: All inertial frames are equivalent with respect to all laws of physics

This postulate concerns “relativeness” of reference frames (principle of relativity).

It follows directly from the absence of a universal frame of reference.

A place moving with constant velocity are the same as those in a stationary place.

Uniqueness of light –the speed of light is the same for all observers whether moving or not. The speed of light is an invariant.

Irrelevance of Velocity –there is no absolute reference frame. All frames are equivalent with respect to the laws of physics.

Herman Bondi labelled the 2 postulates respectively:

Space, Time, Mass and Energy according to Einstein

Length/Space Contraction The length of an object is maximum when

measured in a frame which is at rest; the length is minimum when measured in a moving reference frame.

L = L √1 – v / c

0

_______22

Time Dilation Time is affected by relative motion. Time runs slower in a moving reference

frame than in a stationary frame.

t’ = t √ 1 – v / c

_______2 2

_______

Relativity of Mass Classical physics regard mass as

constant, but mass according to relativity is also dependent on motion. Therefore, the mass of a body changes as the body is set into motion.

m = m √ 1 – v / c

*Nothing can exceed the speed of light; it is the limit to which moving objects can approach.

0______________2 2

Equivalence of Mass and Energy Mass is a form of energy. E = mc shows that

1kg of mass = 9 X 10 J

Significance of the Special Theory of Relativity:

1.) Effect of Newtonian Mechanics 2.) The practical use of relativity is in atomic

and nuclear physics. 3.) Philosophical impact on the course of

physical theory. 4.) The idea of ether had to be discarded.

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Experimental results that support the Special theory of Relativity:

1.) Radioactive Particle Experiments

2.) Elementary Particle Experiments

3.) The Cockroft and Walton Experiment

The General Theory of Relativity

Einstein published the General Theory of Relativity which was an attempt to account for the properties of motion in accelerated and noninertial frames of reference.

The basis of this theory is the Principle of Equivalence:

A homogeneous gravitational field is

completely equivalent to a uniformly accelerated reference frame.

Four-Dimensional Space Time; Consequences of The General Theory of Relativity

Space and are dynamic quantities. Space-time is flat in free space. Space-

time is curved or warped near gravitational fields.

Objects that follow the shortest path between two points in a curved space (Geodesics).

Gravity is a consequence of the fact that space-time is curved.

Light rays also follow geodesics. Light is bent by gravitational fields.

Outstanding Consequences of the General Theory of Relativity

The principle of equivalence is the deflection of a light beam in a gravitational field.

Light will accelerate (hence, it is deflected) in a gravitational field.

Other consequences