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From a paper published at the Cornell University Library (published in Phys. Rev D):
There are very few direct experimental tests of the inverse square law of gravity at distances comparable to the scale of the Solar System and beyond. Here we describe a possible space mission optimized to test the inverse square law at a scale of up to 100 AU. This experiment would extend our understanding of gravity to the largest scale that can be reached with a direct probe using known technology. This would provide a powerful test of long-distance modifications of gravity including many theories motivated by dark matter or dark energy.
(Nb: the paper is published in Phys. Rev D, I link to the arxiv article. The form of publication is common where one publishes in arxiv before sending to a journal in order to provide open access to an article published in a subscriber only journal.)
(Score: 1, Interesting) by Anonymous Coward on Wednesday December 02 2015, @01:41AM
They mention Yukawa because it is the form that 1/r^2 forces take when their carriers have mass. In other words, if you can show that gravity takes a Yukawa form, it proves that the graviton has mass. The funny thing is that if gravity has a Yukawa form that can be detected bu such a probe, it might be able to explain dark energy (not going to try to run the numbers, myself), but it makes the dark matter problem worse. Likewise, if you modify gravity to eliminate the need for dark matter, the dark energy problem becomes worse.
Back to Yukawa - the form the potential takes in a Yukawa type theory, up to factors of hbar and c, is exp(-mass * r)/r. For the technically inclined, yes, that is a modified spherical Bessel function of the second kind.
The people who study background radiations would love to put a camera or two (or photometers, at least) on a mission like this because it would be well outside of the solar system's dust cloud that is thought to be the dominant cause of disagreement between the direct vs indirect measures of background radiation in the optical to mid-IR.
(Score: 0) by Anonymous Coward on Wednesday December 02 2015, @03:47AM
Thanks for the reply (I guess a Yukawa fanboi must have been the one to mark it "Troll" :) ). So I see how this makes for a nice test of graviton mass, but what if gravity is 1/r^(2+epsilon) or some sort of polynomial expression?
I'll have to dig into the paper a bit. It isn't very often those theory guys write a paper that talks about real measurements, which is something I can wrap my head around, so as an experimentalist I feel compelled to turn the tables on them and put their feet to the fire for a change. :)
You'd just have to put particle detectors and magnetometers on it. To measure the interstellar environment would be awesome.