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Comment by kristopolous | Hacker News Reader

Let's assume space is curved in a way that it only appears vast and it's an irregular curvature. How would you be able to demonstrate if an object in a photograph is another cycle around the curvature?

For instance, you could be seeing an already observed object at a different incoming angle and thus a trivial comparison would be defeated

I'd think if this question is answerable you could also perhaps demonstrate there are no cycles or repetitions, even irregular ones.

I don't know though, anyone that knows things care to opine? I'm assuming this is theoretically arguable, such as a proof by contradiction or something.

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We can do things to measure the curvature of the universe, everything so far points to complete flatness so if there is curvature and the universe is closed, the radius is much much larger than the observable universe as to make it appear “locally” flat, where “local” is something like 100 billion light years.

How did the measure the curvature of the universe?

By looking at the remnant of the big bang -- measuring the power spectrum of the remaining cosmic microwave background energy, across large angles of sky.

Right, but how can you test assertions at that scale? In the same way that there's quantum physics, couldn't there be non-local or galaxy sized physics working in different ways? If not why?

Rewriting the rules would probably solve a few mysteries. It sounds like an easy out

You look for physics that explains multiple things. A new law to explain each specific phenomena and only that one is probably wrong. You want laws with several unrelated testable consequences.

Physics that boils down to “things are just the way we see them” isn’t much of an explanation. Physics that doesn’t change based on location, direction, scale, etc is important to look for.

Easy outs probably aren’t helpful.

Why isn't helpful? If it accounts for natural phenomena without mystery sauce then we're good. Our familiarity with the millennium long physics of parsec sized systems is rather limited and to presume there aren't factors at play that have variance at that size is rather presumptive.

Has there been an effort to sincerely discard everything, observe only large scale celestial systems, then try to derive things all over again? You may just get classical models but then again, you might not.

I'm familiar with that "shutup we know everything" response and not only do I find it thoroughly unconvincing but it's never been correct given a long enough timeline of scientific inquiry.

The idea that we can demonstrate all the physics of the universe given the surface of a single planet sounds a little irrational.

Look at the Voyager 1 AACS data for instance. Is the data incorrect or is it correct and things are just different in interstellar space?

There have been plenty of attempts to modify gravity, general relativity, etc to explain the anomalous behavior at very large scales. None so far has come close to a satisfying solution which has testable effects and doesn’t introduce inconsistencies with already observed behavior.

Clearly there is a gap between theory and reality, the best candidate right now is that there is a whole lot of matter out there which so far we can only observe through its gravitational effects and which does not interact with electromagnetism.

Without much knowledge it’s easy to say “why don’t you just” but plenty of people have been trying and finding nothing that works or explains anything.

Right, dark matter sounds like nonsense. Talk about undetectable magic stuff.

It sounds like I'll have to find this out the hard way and do the work myself.

I'd be much more likely to believe there's a bizarre almost random mess of an X factor that makes everything nonlinear and noneuclidean at a large enough scale and the reason there's inconsistencies is because there's observational mutations that aren't as obvious as gravitational lensing

Let's see if I'm motivated enough to do it.

I'm not expecting to find anything new but instead to satisfy my skepticism. I can be ridiculous on the level of demonstration I demand to be convinced

You’ll have to learn a whole lot more about what we do know before your skepticism about what we don’t know holds much weight with other people.

The Higgs field and neutrinos are examples of things which we now know definitely exist but are extremely difficult to detect or barely interact with the EM which makes up most of our experience of the universe.

Skepticism of something we can’t see simply because we can’t see it should be tempered because there is plenty of precedence for difficult to detect things which end up very confidently real.

PBS Space Time YouTube videos are a good way to get initial exposure to a lot of what we know now.

I know how you feel, i have some questions about black holes i haven’t found satisfying answers to myself. The only solution is going to be teaching myself general relativity math and doing some simulations, which may or may not ever happen.

> I can be ridiculous on the level of demonstration I demand to be convinced

Unfortunately we don’t always have the luxury of that level of demonstration in physics

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