On a cosmic scale the notion of distance is more subtle than you might think.
New observations of lensed quasars show the Universe is expanding faster than expected. But these results raise questions about the assumptions of our cosmological models.
Matter and antimatter emit the same spectra of light. So how do we know that distant galaxies aren’t made of antimatter?
Was the speed of light much faster in the early universe?
The relativistic effect of gravitational lensing allows astronomers to see the faintest galaxies.
The Universe has no preferred direction, and that’s a good thing.
The rate of cosmic expansion has changed over time. So why does it look like a constantly expanding universe?
Perhaps the Universe began with a big bounce rather than a big bang.
A new survey of more than a million galaxies supports the standard model of cosmology.