Universe is flat

Is the universe flat or donut?
The Universe is actually curved — either positively like a (higher dimensional) sphere or negatively like a horse's saddle — but the scale of its curvature is so large, at least hundreds of times the scale observable to us, that it appears indistinguishable from flat..
Universe theories
A spatially closed universe can expand forever if the vacuum energy density is not zero.
Yes, a universe without dark energy will expand decelerated and collapse into a big crunch.
This is still true if small amounts of vacuum energy, respectively ΩΛ is added..
Universe theories
the term “Flat” doesn't mean it's .
1. D flat surface like the table top, but it means that it's an euclidean space that every two parallel line will remain parallel if they extended to infinity, also any triangle stretched across the universe its angle always add up to 180 degrees
What does it mean that the universe is flat?
Most cosmological evidence points to the universe's density as being just right — the equivalent of around six protons per 1.3 cubic yards — and that it expands in every direction without curving positively or negatively.
In other words, the universe is flat._{Feb 23, 2021}.
Which dimension is flat?
Two Dimensions: A flat plane or shape is two-dimensional..
The Universe is actually curved — either positively like a (higher dimensional) sphere or negatively like a horse's saddle — but the scale of its curvature is so large, at least hundreds of times the scale observable to us, that it appears indistinguishable from flat.

In a universe with zero curvature, the local geometry is flat. The most obvious global structure is that of Euclidean space, which is infinite in extent. Flat universes that are finite in extent include the torus and Klein bottle.

The current theoretical belief (because it is predicted by the theory of cosmic inflation) is that the universe is flat, with exactly the amount of mass required to stop the expansion (the corresponding average critical density that would just stop the is called the closure density).

Thus, the universe has no bounds and will also expand forever, but with the rate of expansion gradually approaching zero after an infinite amount of time. This is termed a flat universe or a Euclidian universe (because the usual geometry of non-curved surfaces that we learn in high school is called Euclidian geometry).

Universe is flat

Is the universe flat or donut?

Universe theories

Universe theories

What does it mean that the universe is flat?

Which dimension is flat?