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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?
(Score: 2) by Lester on Saturday October 06 2018, @09:26AM (1 child)
String theory is not a theory, it is an hypothesis. To became a theory it has to be proven with experiments.
In fact, it is not even a hypothesis. A hypothesis needs to be falsifiable [wikipedia.org], but no one has yet come out with "I predict that if we try this experiment, according with strings theory, we'll get this result, contrary to current physics expected results". Not even "That observed phenomenon that is unexplainable with current physics, can be explained with strings hypothesis". Moreover. They still haven't formulate a clear hypothesis. They are still building the math structure that fits in current known reality, that explains current observations.
String theory is just a research path that maybe some day become an hypothesis. The most brilliant minds have been exploring that path for more than 20 years and still don't have a hypothesis. Maybe it's time to say "This was the wrong path"
(Score: 2) by Immerman on Monday October 08 2018, @04:23PM
There are theories and there are Theories. Even many scientists talk about their pet theories, which have none of the rigorous, independently confirmed experimental evidence to be generally regarded as a Theory.
As for saying "this was the wrong path" - why would you do that when you have a theory that is completely consistent with observed evidence and offers solid explanations for the "magic numbers" that plague the QM? Nothing in the universe guarantees that an accurate explanation will be easily testable.
And it's not like *all* the most brilliant minds have been chasing testable hypotheses for the same theory - we've got several QM theories being explored, *none* of which have come up with a definitively falsifiable hypothesis (well, except that, if this new data is taken as valid, it's just falsified any theories that require that gravity be able to "leak out" into other macro-dimensions.)