# Thread: How would the Michelson-Morley experiment turn out if...

1. ..... if the entire interferometer apparatus were encased in solid glass?

Under those circumstances, the light would clearly be moving through a medium of some kind (glass), and not just the vacuum of space. Would the two beams of light still match up at the end of their trip, or would the passage through a medium that is being "dragged" with the apparatus still not create the desired effect?

2.

3. Originally Posted by kojax
..... if the entire interferometer apparatus were encased in solid glass?

Under those circumstances, the light would clearly be moving through a medium of some kind (glass), and not just the vacuum of space. Would the two beams of light still match up at the end of their trip, or would the passage through a medium that is being "dragged" with the apparatus still not create the desired effect?
There would be no relative motion between the apparatus and the glass, hence no effect on the experiment.

The speed of light in a medium is a completely different animal from the speed of light in a vacuum. In a vacuum you are looking at the speed of a photon. In a medium you are looking at a complex process of interaction between photons and electrons.

4. So, if Aether drag theory were true, it would fully account for the results of the experiment? (I'll admit that's a really big "if", unless someone could propose a sensible reason why the Aether is being dragged.)

5. The two beams of light would still match up at the same time at the end of the trip. The apparatus will undergo a physical contraction in the direction of its motion the same as it would if it was made out of any other material. The light beams are also slowed down the same amount in all directions, so there would be no difference, just a longer time for them to reach other.

PS: The Ether obviously exists, but it does not "drag". Dragging is not the right explanation as to why motion cannot be compared to the Ether.

6. Originally Posted by Waveman28
The apparatus will undergo a physical contraction in the direction of its motion ...
If that is true, then as the table rotates the shorter arm gets longer, and the
longer arm gets shorter, thus producing a varying sequence of wave intensities
from maximum to minimum. This was not observed!
The MM test was looking for interference which only requires a minimum 1/2 wave change.
It was not proving the distances were equal, in fact the test has been done with
unequal path lengths.

7. Suppose with the two slits experiment one slit is "closed" with glass the other not. I would think you could still see the lightspots on the screen behind it.
So why would the light that goes through a glass bar need to be a case of "different fotons" then the light that goes besides it ?

8. Originally Posted by phyti
Originally Posted by Waveman28
The apparatus will undergo a physical contraction in the direction of its motion ...
If that is true, then as the table rotates the shorter arm gets longer, and the
longer arm gets shorter, thus producing a varying sequence of wave intensities
from maximum to minimum. This was not observed!
The MM test was looking for interference which only requires a minimum 1/2 wave change.
It was not proving the distances were equal, in fact the test has been done with
unequal path lengths.
I dont think you know what your talking about. Physical contraction is still valid. Thats the whole point, when the apparatus is rotated 90 degrees, the path lengths change so that any change in wave intensities is cancelled, thus making absolute linear motion undetectable. It comes to the same conclusions as Special Relativity, it just explains the phenomena in a much more sensible, logical way. By the way, that second experiment you were referring to is called the Kennedy-Thorndike experiment, and making one arm shorter than the other makes absolutely no difference on the experiment.

9. Originally Posted by Waveman28
... and making one arm shorter than the other makes absolutely no difference on the experiment.
If that's true, then why say one length contracts?

10. Originally Posted by phyti
Originally Posted by Waveman28
... and making one arm shorter than the other makes absolutely no difference on the experiment.
If that's true, then why say one length contracts?
Im talking about making the two arm lengths actually different from eachother before the experiment even starts, not length contraction due to velocity. Thats what the Kennedy thorndike experiment did, and it made no difference. Physical length contraction due to velocity does make a difference. You cant say length contraction itself doesnt happen because it has been experimentally confirmed!!

11. Originally Posted by Waveman28
Im talking about making the two arm lengths actually different from eachother before the experiment even starts, not length contraction due to velocity. Thats what the Kennedy thorndike experiment did, and it made no difference. Physical length contraction due to velocity does make a difference. You cant say length contraction itself doesnt happen because it has been experimentally confirmed!!
First, don't take this as an assault on your opinion, you just happened to make the statement here about length contraction.
Second, I don't believe in a physical length contraction or expansion, it's just a measurement thing.

To help clarify the last post, if there is no interference detected when the path lengths are initially equal or different, or when they vary while they exchange orientations, then length contraction is no answer, because interference or
its absence becomes independent of length.
Also, the interference process is surely not prohibited by SR according to the 1st postulate!

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