Would the Pendulum's Shadow Vibrate at PHz on a Moving Wall?

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Discussion Overview

The discussion explores the behavior of a pendulum's shadow on a moving wall, particularly focusing on the implications of relativistic speeds and the nature of light and shadows. The scope includes theoretical considerations of physics and relativity.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant proposes a scenario involving a pendulum vibrating at PHz and questions whether its shadow would vibrate at the same frequency on a moving wall, regardless of the wall's speed.
  • Another participant argues that if the pendulum and light source are stationary while the wall moves toward the pendulum, the shadow would not vibrate at the same speed.
  • A subsequent post questions the implications of both the wall and light source moving at significant fractions of the speed of light, suggesting that the shadow could vibrate at light speed under certain conditions.
  • One participant asserts that shadows can move faster than light without conflicting with relativity, emphasizing that no actual particles exceed light speed and that faster-than-light (FTL) shadows cannot transmit information.
  • Another participant elaborates on the concept of FTL shadows, using an analogy of a laser dot on the moon to illustrate that while the dot can appear to move faster than light, it does not allow for faster-than-light communication.

Areas of Agreement / Disagreement

Participants express differing views on the behavior of the pendulum's shadow in relation to the speed of the wall and light source. There is no consensus on whether the shadow can vibrate at the same frequency as the pendulum or the implications of relativistic speeds on this phenomenon.

Contextual Notes

The discussion involves assumptions about the nature of light, shadows, and relativistic effects that are not fully resolved. The implications of speed and motion on the pendulum's shadow remain unclear and are subject to interpretation.

Hippasos
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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!
 
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if the pendulum and light source are stationary and the wall is moving toward the pendulum then the answer is no.
 
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!
 
There is no conflict with relativity, since no actual particles are moving faster than light here, and an FTL shadow cannot be used to transmit information FTL.

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.
 

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