Light is this stuff made out of photons and that makes it a really funny thing.
Why is it funny? Well for one we don't know if photons don't have a tiny bit of mass after all...if they do then light can't move with the speed of light.
Everyone knows there's antimater, so protons have anti-protons, electrons have anti-electrons and so on. But photons have photons, they are their own antiparticles.
It takes any photon 100 mln years to get from the core of the sun to its surface, and only 5 minutes to get from there to Earth.
The Univers started 13.5 mld years ago, so if nothing moves faster then light then the cosmos should be 13.5 mld lightyears across? Right?
Wrong! In fact it is way larger.
Funny.
About 13.7 is closer than 13.5. Also, it takes a little more than 8 minutes for light to get to Earth, not 5.
And that would be radius of the universe, not the full diameter. It would 13.7 * 2, or 27.4 billion light years. But really, those are all theoretical models - some scientists would say it is a perfect sphere, some would say it is relatively flat, some would say it is hyperbolic. Some would say the matter expanded in just 1 direction, not in every direction. You can't say that it is larger than the speed of light allows it to be, though.
