Eli5 If the universe expanded from a single point why do scientists say its flat and not spherical?

Question

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.

In: 229

Answer 1

The universe is “flat” in a higher dimensional sense. When we think of our existence on Earth, we’re thinking of being 3D beings sitting on the 2D surface of a 3D object.

When physicists talk about the shape of the universe, they’re talking about the experience of sitting on the 3D surface of a 4D object. There is observable curvature in space-time due to black holes and such, but we’ve come to the conclusion that in the absence of gravity or energy, there is no curvature.

Edit: I totally failed at the “explain like I’m 5” part, I’ll admit.