What shape is the Universe?
We don’t know—this is another big unanswered question in astronomy.
The good news is that we have some theories and we’re working on observations and experiments to test them. The bad news is that thinking about the shape of the Universe is extremely difficult. You have to forget simple shapes such as spheres and cubes, and start thinking about shapes in more than three dimensions.
If you imagine 3-dimensional space represented as a 2-dimensional surface, the Universe can be one of three shapes (pictured right):
- Closed and finite in size.
- Open and probably infinite in size.
- Flat and probably infinite in size.