Special Relativity deals with objects or systems which are either moving at constant speed with respect to one another (unaccelerated systems) or which are not moving at all. (with a constant speed of zero)
Fundamental Postulates of the Special Theory.
- First Postulate - Ether cannot be detected.
How did Einstein propose this?
ex: 1. You are looking down into a stream from a bridge overhead. As you gaze into the water at your reflection, it won't be long until you believe that you and the bridge are gliding smoothly along and the stream is calm. However, you KNOW that the bridge is stationary and the water is moving.
ex: 2. You are traveling away from earth at 5000mph and you continue until the Earth is out of sight. Then another rocket appears behind you, overtaking you. That person thinks that you aren't moving. You know that he is moving at a different rate than you because you see him approaching you. There is no way to determine his or your speed without a motionless object.
Einstein: All motion is relative.
There is no ABOSOLUTE MOTION, just motion relative to something else.
A stationary ether would possess absolute motion because it would be the one thing in the universe which would be motionless.
- Second Postulate - The velocity of light is always constant relative to an observer.
A boy throws a baseball at 15mph relative to him.
ex: If he is standing on a railroad flat car, the velocity of the ball is 15mph to him; but the speed of the ball relative to the ground will be more or less depending on the train's velocity and direction of motion.
Contraction of length: L1 = Lsqrt(1-(v^2/c^2))
L1 = LengthA obtains for B
L = B's original lenght
V = relative velocity
C = velocity of light
Mass Increases with Velocity
M1 = M/sqrt(1-(v^2.c^2))
M1 = A botains for B's mass
M = B's original or rest mass
V = relative velocities
C = velocity of light
Addition of Velocities
Vab = Va + Vb
t1 = tsqrt(1-(v^2/c^2))
t1 = time A reads for B's clock
t = time A reads for his own clock
The higher the relative velocity of A + B, the slower B appears to go.
Time Dilation Effect - if two observers are moving at a constant velocity relative to each other, it appears to each that the others time processes are slowed down.
The Special Theory emphasizes that time is different for different at different positions not moving relative to each other.