Why would it only expand in one plane not every direction like you’d expect?
Also how is a flat universe even possible? Surely since we live in 3 dimensions the universe needs to be a 3 dimensional shape.
Im probably misunderstanding what physicists are trying to say but that’s why im here.
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The universe did not expand from a single point. We do not know if the universe is infinite or not. If it is infinite now, then it was infinite in the beginning.
The “observable universe” is a region of the universe that we can see from earth in some form, be it visible light or some other wavelength. We can never see anything beyond the observable universe so we can never directly know if the universe if infinite or not.
The observable universe started as a point-like region. That is, everything we can see was once squashed down into a very tiny region of space and expanded rapidly directly after the big bang.
When we say the universe is flat, we are not talking about the shape of the the universe as a whole, but the geometric properties of space. In a flat universe parrallel lines will never meet (think of parrallel lines on a flat sheet of paper clearly not meeting). In a non flat universe paralled lines could meet (think of lines of lattitude on a globe meeting at the poles).
It’s important to undertand if the universe is flat or not so we can correctly understand the movement of photons over a vast distance. Light always follows a straight line, and in a flat universe a straight line doesn’t follow a curve, where as in a non flat universe it would. So if we observe light following a curve we then know it’s due to a gravitational distortion of space rather than the geometric curve itself in space.
We believe the universe is flat because everywhere we look we see the same average density in space. If space was curved, places foar off in the distance would look more or less dense than or local space.
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