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As well as what ISL said, if the universe is toroidial it seems like it's larger than our visible horizon. While images of an individual galaxy might be hard to
by jerf 5y ago
As well as what ISL said, if the universe is toroidial it seems like it's larger than our visible horizon. While images of an individual galaxy might be hard to tell if they are repeated, we can see enough of the structure of the universe that if our visible horizon was much larger than the real value of the universe and there was wrapping going on, we'd see it. This isn't the exact sort of video I'm looking for, but it's close enough to what I'm talking about: https://www.youtube.com/watch?v=rENyyRwxpHo https://www.youtube.com/watch?v=rENyyRwxpHo Everywhere we look we see distinct structures.
It is not a bad thought, though. It may well do some sort of wrapping around, just at a larger scale than we can see. It's an open problem.
- hnthrowaway0315 5y agoWatching that video will make anyone humble.
- Keyframe 5y agoEverywhere we look we see distinct structures. This might be us being in an isotropic bubble where outside of the bubble is forever gone for us to see due to expansion of universe... Not sure how CMBR falls into that however.
- jerf 5y agoHence "it seems like it's larger than our visible horizon", "at a larger scale than we can see", and "It's an open problem".
- idealmedtech 5y agoIt's been over a decade since my cosmology class, so forgive any errors, but isn't there a constant that describes the curvature of the universe [1], which so far has been calculated as "flat"? That's not to say we'll ever truly know, since you need infinite precision to rule out hyperbolic or spherical geometry, but in a flat universe, how can you have toroidal geometry? Per [2]: > The actual value for critical density value is measured as ρcritical = 9.47×10−27 kg m−3. From these values, within experimental error, the universe seems to be flat. [1] - https://en.m.wikipedia.org/wiki/Friedmann_equations#Density_parameter https://en.m.wikipedia.org/wiki/Friedmann_equations#Density_... [2] - https://en.m.wikipedia.org/wiki/Shape_of_the_universe https://en.m.wikipedia.org/wiki/Shape_of_the_universe
- Keysh 5y agoIt’s actually no problem mathematically to have toroidal topology and flat geometry. (The classic Asteroids video game, where your ship can go off the top of the screen and come in at the bottom, or similarly with the left and right edges, is an example of a flat 2D space with the topology of a torus.)
- dm319 5y agoWe're talking about being toriodal or curved in a 4th spatial dimension I assume?