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posted by martyb on Friday October 05 2018, @09:55PM   Printer-friendly
from the 4-dimensions-ought-to-be-enough-for-anybody dept.

Scientists have managed to constrain the possible number of dimensions of our universe to 3+1 (3 spatial and 1 time).
According to a new paper on Arxiv https://arxiv.org/abs/1801.08160
A recent merger of neutron stars that was observed in the visible spectrum, as well as with gravity waves, was used to determine that there are no extra dimensions for gravity to leak into. This reinforces our current models based on 3+1 to an extremely high degree of certainty and essentially rules out any theory that requires extra dimensions in order to function.

Quoting the paper:

The observation of GW170817 in both gravitational and electromagnetic waves provides a number of unique tests of general relativity. One question we can answer with this event is: Do large-wavelength gravitational waves and short-frequency photons experience the same number of spacetime dimensions? In models that include additional non-compact spacetime dimensions, as the gravitational waves propagate, they "leak" into the extra dimensions, leading to a reduction in the amplitude of the observed gravitational waves, and a commensurate systematic error in the inferred distance to the gravitational wave source....

The short of it was that there was absolutely no evidence for electromagnetism and gravity to be propagating through a different number of dimensions than the expected 3+1.

These are just some really cool and unexpected results; in my case I was a big supporter of brane theory until this result came out. Now, I don't know what to think. Gravity is too weak to make any sense at all. What do you think?


Original Submission

 
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  • (Score: 0) by Anonymous Coward on Saturday October 06 2018, @11:54PM

    by Anonymous Coward on Saturday October 06 2018, @11:54PM (#745257)

    A neutron star doesn't have charge -- "neutron" - the star is so dense that distinct atoms and protons and electrons can't exist. Accordingly there's no real electromagnetic force, or at least not like we know it. If that is included in the calculations, then it's different from all other matter and its gravity should be different. So far as we have observed, this is not so.

    It's a weak argument. It doesn't involve the strong/weak force, but it "feels" incorrect. There's also the aspect of energy between bonds having mass (e=mc^2 stuff), where you lose mass converting it to energy when you break certain bonds within the atomic nucleus. This isn't the Higgs field, I don't think, and so isn't tied to the Higgs Boson (which is in everything? but not the Proton? I haven't read enough about the Higgs).

    Just.. doesn't feel right.

    "And what if we had gravity that repelled everything instead of attracted everything?" - then does it repel itself as well? Then it would be spread so thin throughout the universe we'd never be able to detect it.