What Happens to Wave Measurements When You Sail at the Speed of Light?

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Discussion Overview

The discussion revolves around a thought experiment involving wave measurements from a boat moving at a specific speed relative to the waves. Participants explore the implications of motion on wave properties such as wavelength and frequency, and how these concepts relate to the constancy of the speed of light.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant proposes a scenario where they measure wave properties from a stationary boat and hypothesizes that sailing into the waves at the same speed as the wave speed would result in observing the waves at twice the speed, leading to a halving of the wavelength and a doubling of the frequency.
  • Another participant questions the initial hypothesis by asking why the wavelength would change and whether it would double if the boat moved in the opposite direction.
  • A third participant identifies the classical Doppler effect in the original argument and points out that the speed of water waves is not invariant across observers, contrasting it with the speed of light, which is an axiom supported by experimental success.
  • A later reply reiterates the original hypothesis about wavelength and frequency changes while suggesting that something else must be changing, inviting further contemplation on the matter.

Areas of Agreement / Disagreement

Participants express differing views on the effects of motion on wave properties, with no consensus reached on the implications for the speed of light or the nature of wave behavior in this context.

Contextual Notes

Participants reference the classical Doppler effect and the constancy of the speed of light, but the discussion remains unresolved regarding the application of these concepts to the thought experiment presented.

Gaz
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Hi I want to create a thought experiment involving waves of any kind. I am going to create a thought experiment I am on a boat that is at rest in the ocean. I am standing on the boat measuring the size of the waves and the frequency. So I measure the wave along the side of my boat to have a length of 6 meters and a frequency of 1 per second. So i deduce the wave is traveling at 6 m/p/s (6 meters per second).

Now I sail my boat at 6 m/p/s into the waves what is the outcome ?

My Hypothesis is I would see the waves passing me by at twice the speed so the wavelength is 3 m/p/ half s (3 meters per half second) and as the wavelength half's the frequency doubles to 2 per second.
So I conclude when you measure a wave you cannot add your speed to the wave as your motion has to be added or deducted from the wavelength which will effect the frequency and that is why the speed of light is constant to all observers. Any speed added by your motion is simply deducted from the wavelength and added to frequency. So the speed of light remains the same regardless of your motion. And it is not time that changes?
 
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Gaz said:
as the wavelength halves
Why would the wavelength be different ? Would the wavelength double if you go in the opposite direction ?
 
First, what you are describing is called the classical (non-relativistic) Doppler effect. If you read about it, in any standard physics textbook, you will see where you are missing the point.
Second, you made a big leap when you concluded that the speed of light is the same for all observers, by the strength of your argument, which is based on material (water) waves. The speed of water waves is not the same for all observers. You should know that there is no explanation for the speed of light being the same for all (inertial) observers. It is an axiom, the truth of which is borne out by the success of experiments.
 
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Gaz said:
My Hypothesis is I would see the waves passing me by at twice the speed so the wavelength is 3 m/p/ half s (3 meters per half second) and as the wavelength half's the frequency doubles to 2 per second.

so as the other two have suggested, the wavelength isn't changing, and for you nor is time
so that leaves one choice for what is changing ... can you think what that is and why ?
You have answered it without realising :wink:
Dave
 

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