0
$\begingroup$

When we say the universe is flat, we mean just the observable universe. So that doesn’t mean the shape of the whole universe is also flat (ie. it can be curved on much larger scale)

Is Flatness problem still considered a problem?

$\endgroup$
1
$\begingroup$

Yes, it is. It's a problem because of the cosmological principle, which says, effectively, that we are not observing the universe from some special, privileged position: what we see is what any observer (at the same distance in time from the big bang) would see. So if we observe the universe to be spatially flat so does anyone, and so it is spatially flat.

$\endgroup$
  • $\begingroup$ I mean the universe can be curved/not flat on large scale even the observers on any position see it as flat. $\endgroup$ – parker Feb 8 '18 at 11:58
  • $\begingroup$ If the curvature was low enough no observer could detect without really sensitive equipment. $\endgroup$ – PyRulez Feb 9 '18 at 4:56
  • 1
    $\begingroup$ @parker well yes, measurements can only ever place bounds on values: I had assumed you meant something more interesting than that. $\endgroup$ – tfb Feb 9 '18 at 10:23
1
$\begingroup$

Well yes, but that is how inflation proposes a solution to the flatness problem. It suggests that the universe is locally flat (where local means the bit we can see - the observable universe) and that any curvature could only be apparent on much larger scales.

So if you accept the inflationary hypothesis then the flatness of the observable universe isn't a problem.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.