Craigus comments on Open thread, Oct. 5 - Oct. 11, 2015 - Less Wrong
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Potential crank warning; non-physicist proposing experiments. Sorry if I'm way off-base here, please let me know where I've gone wrong.
I was contemplating MWI and dark matter, and wondered if dark matter was just the gravitational influence of matter in other universes, where the other universes' matter is distributed differently to ours. Google tells me that others have proposed theories like this, but I can't find if anyone has ever tried to test it.
Has anyone ever tried to test this directly? We have gravimeters sensitive enough that one "detected the gradual increase in surface gravity as workmen cleared snow from its laboratory roof".
Imagine an experiment was run using a source of quantum-random binary data, with the protocol to move a large mass close to and further away from the gravimeter based on the quantum data. My expectation based on this theory is that the gravimeter would measure:
The experimenters would want to repeat the quantum mass movements many times, so that as many universes as possible are able to measure both the 'close to' and 'further away' positions of the mass at least once. (If the experiment only did 5 measurements, 2 out of 32 universes would have their experiment be 'mass is always close' or 'mass is always further away', and therefore don't get the full benefit of the experiment.
Interestingly if this theory were true, experiments could be run where the gravimeter and mass are used to communicate between universes.
MWI doesn't work that way. Universes are close iff the particles are in about the same place.
Is this the sort of experiment in which you would need macroscopically different 'universes' separated from each other by single quantum events, such that the thermal noise/interaction with the environment of the large experimental mass must be dealt with?
There have been some similar ideas, but not related to MWI - as DanielLC says, the "distance" that separates two different states of the universe does not behave like we commonly imagine distance between "parallel worlds" to behave.
However, something that can behave like that is these extra spatial dimensions proposed by string theory, brane theory, etc. See wikipedia. I'm sure someone has proposed this as an explanation for dark matter.