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## Physics library

### Unit 16: Lesson 1

Michelson and Morley's luminiferous ether experiment

# Potential ways to detect an ether wind

Thinking about how Earth's relative velocity to hypothetical luminiferous ether can be used to detect ether.

## Want to join the conversation?

• What exactly is an "ether"?
• The ether is a hypothetical medium filling all space for transferring both electromagnetic and gravitational waves. It comes from the Greek word αἰθήρ, meaning upper air. The luminiferous ether, the one Sal was referencing, is the hypothetical medium for light.
• Is medium always has a direction? Particles in solid material is not moving, so it means it's not having a direction, but it can be a medium for sound. Why can't we think ether wind like that?
• But the point Sal was making was that we are moving relative to the sun and to the center of Milky way. So if it's fixed in some way, then we are moving relative to it, and so it is moving relative to us. If the medium wasn't moving relative to us, then that would be a massive coincidence. And even then, it would have to be moving relative to the sun, in which case we would still see some effect as light passed through it.
• Did we know that light has a constant velocity in the nineteenth century? If we did shouldn't we be focusing on wavelength of light? Because speed of light in space is around 3*10^8 m/s and it will remain constant by adjusting its wavelength. Shouldn't we search for possible redshift or blueshift rather than speed ? Just saying but if we did not know the speed remained constant its a whole different story.
• Obviously that was not known, which is why there were efforts to find the effect of the ether. Maxwell determined his equations around 1870, and that was the first indication that the speed of light was constant in some way, but most people still understood it to mean that the speed was constant relative to some medium - the ether. That's how other waves work, so it would be reasonable to guess that light would work that way as well. But it doesn't.
• Could we plot our (the earth's) velocity/ position with respect to space graphically, if we find an origin point of the universe in space? (In this case an origin point means the "place" where the Big Bang occurred.)
• Of course we can't detect the exactly point where the big bang had occurred because velocity can work at any direction even with respect to space graphically but by observing our path around the sun we can use the probability to find the probable points where the big bang had occurred!
But I am to greet you for asking this interesting question!
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• this may seem weird, but how can scientist compare ether to the mediums present on earth??..,. ether might be having different properties from that to the mediums present on earth.
• It definitely would have to have different properties, if it existed. THat's the point.
• Would it not be possible that ether wind was affecting the frequency of light / photons instead of its speed?
• can the luminiferous ether be similar to the fabric of space and time?
• No, the luminiferous ether was a way to have an absolute rest frame against which you could measure velocity against. Space-time doesn't give you that.
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• How is it possible to know the speed of ether wind in order to compare with the speed of light ?
• what if the ether itself is stationary....and there is no ether wind?
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• The earth is moving through space. If the ether is all around in space, the earth must be moving through it. That's where the wind comes from.
• What is ether wind? I got from this video that it was the "wind"/"current" we circle the sun around, and the sun circles the earth around. If I'm wrong, please explain why and what ether wind is. Also, luminiferous ether is the medium, right? And the waves are the disturbance? Thanks to anyone who answer all the questions!
(1 vote)