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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, @12:00AM (8 children)

    by Anonymous Coward on Saturday October 06 2018, @12:00AM (#744853)

    It was predicted that graviational waves would lose amplitude if there are extra dimensions.

    Anyone could watch waves on a lake or ocean and see they lose amplitude. This is not an impressive prediction.

  • (Score: 0) by Anonymous Coward on Saturday October 06 2018, @01:23AM (1 child)

    by Anonymous Coward on Saturday October 06 2018, @01:23AM (#744886)

    No what he means is that if gravity is passing through dimensions that EM is not, then it would lose amplitude faster than EM.
    Since EM is adequately described by models containing 3+1 dimensions, it is assumed that if EM and Gravity were passing through a different number of dimensions then there would be a greater dropoff in the higher dimensional force relative to the lower dimensional force.

    What was found was that gravity and EM both drop off at the same rate, ergo they share n-dimensionality and since EM is known to be 4 dimensional, then gravity must be too.

    One of the major explanations thus far for gravity's weakness has been that perhaps it was as strong as the other forces, but most of that force was leaking into a higher dimension.
    This is now disproven to a high degree of certainty

    • (Score: 0) by Anonymous Coward on Saturday October 06 2018, @04:41PM

      by Anonymous Coward on Saturday October 06 2018, @04:41PM (#745081)

      EM is adequately described by models containing 3+1 dimensions

      Pretty sure there is no spacetime in quantum mechanics.

  • (Score: 0) by Anonymous Coward on Saturday October 06 2018, @04:01AM (3 children)

    by Anonymous Coward on Saturday October 06 2018, @04:01AM (#744951)

    Yes, we know. It'll never be as snazzy as the grand unified theory known as electric universe. Damn those NASA scientists for refusing to fund an expedition to the Antarctic ice wall and for refusing to give out telescope time to test... whatever pre-dictions electric universe makes.

    Where's our electric universe AC? I'm not going to click a video, so fuhgeddaboudit. I just want to know one thing falsifiable thing that electric universe predicts. I'm certain there must be a mountain of those, so just give us one without telling us to sit through a half hour of some butthurt incel going on and on about how much smarter he is than those dumb scientists.

    Though I find it interesting that string theory can be seriously considered when it doesn't make any predictions (I know of anyway) either. (Or rather, string theory's problem from what I understand is that tweaking the parameters allow it to predict every possible thing imaginable without helping us understand which set of parameters fits the observable universe and why nature set the parameters that particular way.)

    • (Score: 0) by Anonymous Coward on Saturday October 06 2018, @11:14AM (1 child)

      by Anonymous Coward on Saturday October 06 2018, @11:14AM (#745005)

      String theory makes loads of predictions. The problem with string theory is that the predictions it makes that go beyond the standard model are very hard and possibly impossible to test at the moment.
      In fact one prediction of an extension of string theory called "brane theory" was just disproven by the above paper although they don't say it directly.
      In essence, brane theory posited that the string are higher dimensional and sitting on n-branes.

      2 possibilities for higher dimensions, either they are essentially everywhere like the 3+1 we know of, or they are curled up.
      This just disproved the "essentially everywhere", and thus greatly limits extensions to string theory, specifically any that rely on higher dimensional branes.

      Oddly enough something that was killed earlier called Kaluza Klein theory wherein gravity was unified with electromagnetism by extending electromagnetism into an additional dimension, just gained support. This is because the test has verified that electromagnetism and gravity share n-dimensionality.
      It did not actually verify that there are only 3+1 dimensions, it merely verified that EM and G slog through the same dimensions.
      https://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory [wikipedia.org]

      • (Score: 0) by Anonymous Coward on Saturday October 06 2018, @04:49PM

        by Anonymous Coward on Saturday October 06 2018, @04:49PM (#745085)

        Every time a string theory "prediction" is disproved they say: "Oh. Well, in this other version of string theory we predict exactly the result you just observed". String theory is infinitely flexible and has never successfully predicted anything beforehand, only post-dictions.

    • (Score: 0) by Anonymous Coward on Saturday October 06 2018, @04:45PM

      by Anonymous Coward on Saturday October 06 2018, @04:45PM (#745084)

      whatever pre-dictions electric universe makes.

      They predicted the philae lander would bounce off the comet (Rosetta Mission) since the scientists told the engineers the surface would be icy. The EU people said that's BS, the surface will be much harder rock.

      That's when I started paying attention to them. Real world consequences.

  • (Score: 2) by wonkey_monkey on Saturday October 06 2018, @10:53AM (1 child)

    by wonkey_monkey (279) on Saturday October 06 2018, @10:53AM (#744996) Homepage

    Anyone could watch waves on a lake or ocean and see they lose amplitude.

    Look at you, getting it all ass-backwards just like the other guy.

    --
    systemd is Roko's Basilisk
    • (Score: 0) by Anonymous Coward on Saturday October 06 2018, @05:19PM

      by Anonymous Coward on Saturday October 06 2018, @05:19PM (#745099)

      Is this that flat earth theory? Are you saying that because I'm watching something through curved eyeballs and camera lenses it creates an illusion that the earth is curved?