1. Relativity

2. Light Clock
Einstein’s postulate is that the speed of light is constant in all inertial frames.
Use light to keep time.
Official standard

3. Moving Clock The light on the moving rocket takes a longer path.
The apparent time is longer on the moving rocket.

4. Lorentz Factor
The relation between the two times is known as the Lorentz factor.
This results in time dilation.
Confirmed on Shuttle

5. Length Contraction
Light traveling the length of B’s ruler takes less time as A sees B.
Time dilation
Constant light speed
Lengths are shorter in motion.

6. The Twin Paradox Consider twins Gozlo and Spedo.
Gozlo stays and Spedo travels.
Gozlo sees Spedo’s clock run slow, so Spedo is younger.
Isn’t Gozlo younger by Spedo’s clock?
No, since Spedo accelerated to change direction.
Not inertial frame

7. Energy from Mass We think of energy due to motion.
Relativity uses Lorentz factor
Gamma = 1 in rest frame
Rest energy exists in an object’s inertial frame.
No velocity
Just mass 7

8. Light Curve An accelerating object would see light bend.
Gravity must bend light, too.
Equivalence principle
Measured in 1919 solar eclipse

9. Space Curve Mass in space cause space to stretch nearby.
Gravity causes time dilation like velocity.
GPS clock corrections