Why is the Milky Way flat?
84229
Why the galaxies form 2D planes (or spiral-like) instead of 3D balls (or spherical-like)?
45057
How far away must a galaxy be for its light never to reach us due to the expansion of the universe?
143493
Will gravity pull together two bodies from the other side of an empty universe?
51742
What is the curvature of an empty universe?
2842
Photons from stars--how do they fill in such large angular distances?
92997
If dark matter only interacts with gravity, why doesn't it all clump together in a single point?
45708
Why do far away objects appear to move slowly in comparison to nearby objects?
114934
Bootstrap Paradox in Interstellar
56529
Why are there spectral lines at all?
58986
Why doesn't dark matter affect planetary motion?
142416
Why are stars white?
86302
If light rays obey to the wave equation, why can they be thought as straight lines?
69115
Imaginary line on the Earth is straight or not?
23347
Are all galaxies we see really our Milky Way? Any possibility?
62494
Can general relativity be completely described as a field in a flat space?
91341
Did anyone wonder why there was one planet fewer before beaming down to Ceti Alpha V/VI?
64734
Distribution of Dark Matter around galaxies