# Is spacetime flat?

Is space-time flat and if the answer is yes then how can objects orbit vertically and diagonally(since gravity is the warping of space-time)? Or does it exist from all sides?

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Doug Huffman
Gold Member
Spacetime is not flat.

Matterwave
Gold Member
Space-time itself is not flat. If it were totally flat, the universe would be in a steady state, (well, if it were totally flat everywhere, it would also have to be empty) which it is not. The 3-D slices of space-time, which we call "space" is roughly flat as far as we can tell. This is the statement that the curvature parameter found in the FLRW metric is roughly 0.

Spacetime is definitely not flat. The two dimensional analogies you might see on television and on documentaries are misleading.

The two dimensional visual representation is this:

So just try picturing it better like this, instead:

Space-time isn't flat,
If spacetime is absolutely flat, then if you were to set off in a rocket ship and travel in a single direction, you would eventually get to the universe that's just like the one you're in now, but where you got up an hour later this morning, or where Michael Jackson is still alive. And if you continued on this journey, eventually you would start getting to the other universes with basic physical laws, the other universes of the multiverse. What I belive is It's close to Flat, But not absolute flat

3D of Space Combine with 1D of Time to Form Malinowski space

Matterwave
Gold Member
Space-time isn't flat,
If spacetime is absolutely flat, then if you were to set off in a rocket ship and travel in a single direction, you would eventually get to the universe that's just like the one you're in now, but where you got up an hour later this morning, or where Michael Jackson is still alive. And if you continued on this journey, eventually you would start getting to the other universes with basic physical laws, the other universes of the multiverse. What I belive is It's close to Flat, But not absolute flat

3D of Space Combine with 1D of Time to Form Malinowski space

What? I don't think Einstein talked about multiple universes to which you could travel if space-time is flat.....

Nugatory
Mentor
3D of Space Combine with 1D of Time to Form Minkowski space
You've misunderstood what you read. Minkowski space is the flat uncurved spacetime of special relativity.

What? I don't think Einstein talked about multiple universes to which you could travel if space-time is flat.....
I meant he talked abut Minkowsi space and lorentz transformation

What is the book called?

We visualize space-time in a two dimensional (flat) image, because it's easier to understand that way.
If you stack an infinite amount of those two dimensional space-time fabrics above and below one another, like stacking plates; then you have what would be the the space-time we have around us.

Chronos
Gold Member
You may wish to search the forum for similar questions. This one has been answered more than once.

Chronos