# An experiment.

1. Aug 27, 2008

### Hippasos

Let's experiment with:

A = a very distant source of light

B = pendulum at a given distance from the light source

C = a huge white wall

Let's suppose the pendulum vibrates at PHz.

Let's suppose the white wall is moving in the line of the light source and the pendulum at the very high speed of V.

Would the pendulum's shadow vibrate at the same speed (PHz) on the C regardless of V?

Thanks!

2. Aug 27, 2008

### granpa

if the pendulum and light source are stationary and the wall is moving toward the pendulum then the answer is no.

3. Aug 28, 2008

### Hippasos

Would it be error then if we say:

If the wall is traveling at half light speed towards the light source and the light source is traveling also at half light speed towards the wall the pendulum's (pendulum stationary at the middle) shadow would vibrate at the speed of light?

What would happen to the shadow if both were traveling say like 55% of speed of light?

Thanks again!

4. Aug 28, 2008

### JesseM

5. Aug 28, 2008

### OS Richert

Allow me to double check why. If someone is on the earth, and they speak to someone on the moon through a radio, that is approximately light speed communication. Now if I am flashing a laser dot on the moon, I can make the dot on the moon travel faster the light, but I am still not communicating faster then light, because it takes the time for the laser light to get to the moon before the effect is noticed, in this case, also at light speed.