# What were the intention/conclusions for Michelson-Morley experiment?

Which of the following were the intentions of M&M?

1. to disprove the existence of aether.
2. to show that the aether has no effect on matter and energy and therefore is as good as non-existent.

Feel free to insert more reasons/intentions.

Which of the following were the corollaries/conclusions?

1. Aether indeed does not exist
2. M&M does not prove or disprove the existence of aether.
3. M&M was a pointless experiment.

Feel free to add more corollaries/conclusions.

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I would like to tag this michelson-morley but I probably don't have enough points to create a new tag. – Blessed Geek Aug 22 '12 at 3:48
I'm not sure we need that tag, but anyway... I'm wondering, why do you have a given list of answers to choose from? This reads like a multiple-choice homework question; is it actually from a homework or self-study assignment, or something similar like a practice test? If not, what is the context? Such questions are strongly discouraged around here if you don't put some effort into them yourself. – David Z Aug 22 '12 at 5:00
Did you check Wikipedia before asking? – Qmechanic Aug 22 '12 at 8:59
This whole question is based on a oddly distorted, hindsight-driven view of how things were. It was the 1880's version of the Higgs search: a very hard, cutting edge, painfully technological, expensive, time consuming, delicate measurement of a fairly subtle effect predicted by the best theory going. – dmckee Aug 22 '12 at 15:43

The purpose of the Morley-Michelson experiment was to detect the motion of the lab relatively to the inertial system of the luminiferous aether, i.e. the "aether wind". The theory that the electromagnetic waves were waves of a composite medium – analogously to sound's being made of waves in the air – predicted that the speed of light should change to $c-v$ and $c+v$ if we move relatively to the preferred frame by the speed $v$ (in the direction of light or against it, respectively).

So none of your entries 1,2 in the first list describe the situation correctly. The intent was exactly the opposite (not that it matters too much). The conclusion is 1 in the second list of yours, aether indeed doesn't exist (or doesn't pick a preferred frame) and the electromagnetic waves are waves that don't require any medium and that violate the rules for the additional of velocities (the speed of light is always $c$, not $c\pm v$, regardless of the speed of the source or the detector), except that you should erase "indeed" because no one had expected that result, not even Einstein who was 8 at that time in 1887.

The MM experiment may be viewed as the primary experimental support for special relativity. However, it's also another historical fact that it hasn't played a key role for Einstein while developing special relativity – Einstein's reasoning was entirely theoretical, he didn't refer to the MM experiment, and the only historical evidence that he was actually aware of it was Einstein's reference to a paper by Lorentz that did mention the MM experiment.

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Historically MM didn't even prove relativity. Their calculations were off and so their detection limit on the aether would always be below the measurement error on the apparatus. – Martin Beckett Aug 22 '12 at 15:30
Martin, first, the MM experiment occurred 1887, well before special relativity in 1905, so it's nonsensical to talk about "proving relativity" which wasn't known yet by MM. Second, I think you're wrong, MM had enough accuracy to exclude the aether wind, assuming that the aether frame is heliocentric (or even more moving relatively to the Earth). – Luboš Motl Sep 21 '12 at 14:49
A lot of physical laws were experimentally 'proven' before the theoretical discovery was made. IIRC MM's theory was off and the predicted effect in their experiment was 2x what it would actually be - and their detection limit was only just capable of reaching even their over optimistic limit. – Martin Beckett Sep 21 '12 at 16:22

I think their intention was to detect/measure the aether and it was a surprise to them that there was a negative result.

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## protected by Qmechanic♦Mar 3 '13 at 18:57

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