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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, @12:01AM

    by Anonymous Coward on Saturday October 06 2018, @12:01AM (#744855)
    You don't fall through the floor when you stand on the ground. That kinda gives you an idea of how much stronger the electromagnetic force repelling the electrons of your feet from the electrons of the floor is than the gravitational force pulling you to the centre of the earth is. The difference in relative strength between electromagnetism and gravity is something like 41 orders of magnitude. Let that sink in for a minute. However, there are two more very important things about about gravity that make it somewhat special compared to the other fundamental interactions: 1, it has unlimited range, and 2, it is always attractive. Let those two more facts sink in for another minute. In comparison, the other three interactions are sometimes attractive or sometimes repulsive, or operate at only very short ranges, or both. That means that gravity dominates the larger scale interactions in the universe at the levels of planets and galaxies and governs the large-scale structure of the entire universe. In some cases, it can even win out against all the other forces, as in black holes.