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# The shape of the universe

There are three possible geometries of the universe: closed, open and flat from top to bottom. The closed universe is of finite size and, due to its curvature, traveling far enough in one direction will lead back to one’s starting point. The open and flat universes are infinite and traveling in a constant direction will never lead to the same point.

Universe with positiveÂ curvature. A positivelyÂ curvedÂ universe is described by elliptic geometry, and can be thought of as a three-dimensional hypersphere, or some otherÂ sphericalÂ 3-manifold (such as the PoincarĂ©Â dodecahedralÂ space), all of which are quotients of the 3-sphere.

TheÂ universeÂ could be positively curved, like a sphere. … In aÂ flat universe, Euclidean geometry applies at the very largest scales. ThisÂ meansÂ parallel lines will never meet, and the internal angles of a triangle always add up to exactly 180 degreesâ€”just like you’re used to.

### Is there an edge to the universe?

BallooningÂ universe. But how can theÂ universeÂ be expanding ifÂ thereÂ is no end orÂ edgeÂ to it? … That is, the concentration of matter in theÂ universeÂ is decreasing as theÂ universeÂ expands, she said. That’s because galaxies aren’t moving away from each other through space â€” it’s space itself that is getting bigger.

### Is there an end to space?

WhetherÂ spaceÂ ever ends is a hard question.Â ThereÂ is a limit to theÂ spaceÂ that we can see, because ifÂ thereÂ is stuff beyond 15 – 20 billion light years (the age ofÂ the Universe) the light fromÂ thereÂ hasn’t reached us yet. So we don’t know.

### What is at the center of the universe?

FYI: Where Is TheÂ Center of the Universe? First, it’s important to know that the big bang wasn’t an explosion of matter into empty spaceâ€”it was the rapid expansion of space itself. This means that every single point in theÂ universeÂ appears to be at theÂ center. Think of theÂ universeÂ as an empty balloon with dots on it.