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There are several cosmological models and ideas that deal with our universe's flatness problem, and they usually lead to topics like the Lambda-CDM model, the cosmological constant, vacuum genesis, and all the other interesting aspects of the ultimate fate of the universe.

It seems (maybe just to me) that these are all approaching (but never reaching) the same answer: namely, that the universe really is flat (i.e. Omega = 1, or k = 0), or at least we will continue to measure it as being flat, no matter how good our measurements get. We certainly have not proved that the universe is flat, but we have a lot of observations that suggest something very close to flat, at least for what we can observe.

So, is the current answer to "is the universe flat?" still "we don't know yet"?

What are some bleeding-edge research efforts that are addressing this question? Are there currently any strong movements in the scientific community to call this question one way or the other, or to declare it "unknowable"?

I'm not surprised that there's no consensus, but I have a hard time getting anyone to say "there's no consensus!", much less "there never will be a consensus".

Any help is appreciated!

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You're pushing up against the limits of what science is capable of stating.

Science never actually proves anything to be globally true in the universe. From a philosophical perspective, that's not what it's trying to do. What we do have are theories which could be falsified by future evidence.

What you could do is declare a scientific hypothesis: "the universe is flat." The currently known scientific evidence would not falsify this claim. It fits within the errors on all of our measurements.

If you think about it, to ever prove something to be "true," one would need to have infinitely precise measurement devices which can observe everything. We don't have those, so instead we take measurements and apply statistical models to them.

There's a famous argument in the science of philosophy that to disprove the statement "all swans are white," you merely need to find a black swan. At that point, it doesn't matter how many white swans you have observed, the original hypothesis is false. To prove the universe is not flat, all we need is one undiscovered or unobserved facet of our universe that shows it isn't flat. The swan example, thus, shows the fundamental limit of science. You can never scientifically prove "all swans are white" unless you can observe all swans.

You can, however, make strong arguments that the empirical evidence observed is in line with your hypothesis.

The most modern opinions on the philosophy of science suggest that the scientific community will announce "the universe is flat" as a true statement only once they have sufficiently exhausted the other possibilities such that a respectable scientist would not waste their time gathering further evidence in an attempt to refute the hypothesis. With the amount of unknown still percolating around the cosmological community regarding dark matter and dark energy, it's not too surprising that the elect not to announce a scientific truth at this time.

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  • $\begingroup$ thanks for the answer. It's that "tail of the curve" problem, whereby the "proof" of the flatness requires more scientific rigor than we can expend, but we just can't seem to leave it alone and call it done either. If I was a cosmologist I might feel rather insecure about this hopelessness, or perhaps I would just try that much harder to "observe" myself some dark energy :) $\endgroup$ – SlimsGhost Mar 6 '17 at 22:09

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