Lorentz factor

When you move, your light clock is slower about T times. This is called Lorentz factor.

c is the speed of light.

2a/c=1

This is the light clock, so you always have 1 second.

When you move from A to C, your light clock move slower.

T=2L/c

T is time, and c is the speed of light.

You see Pythagorean theorem.

∴

You see 2a=c from the light clock.

This is called Lorentz factor.