Khan Academy

Scale of the universe 

We learn about how small we really are in the universe. 

Examples are…

it would take a bullet 40 hours to go around the world and it would take a bullet half a year to go around the sun.

He also took one video to explain how small some things are, like bacteria and hair.

After that he talk about the Orion Spur which is 10,000 light years long (part of the Milky Way), he then went to talk about how small that is, then he talked about the known universe, which is about 47 billion light years, and mean while we are a tiny little speck in the universe.

Stars, black holes and galaxies 

First thing we learn about is how stars are formed, the get formed by a massive clouds a atoms slowly getting pulled in by each other’s gravitational pull, until the pressure makes the atoms start to fuse together making heavy up to iron 56 and nickel 56.

The life of our sun 

The sun started out as any other (at this stage the only difference between stars is the sizes of gasses they start out with), where it will burn for several dozen billion years with the core getting smaller (more dense with a bigger mass) and the out side is expanding, until the sun cannot do fusion any more without loosing energy, so the core now consists of iron 56 and nickel 56, it now becomes a red giant, when our sun does this it will swallow up the earth. It will burn for a couple hundred thousand years, and then it will become white dwarf then a black dwarf (a black dwarf is when all the energy is out of the white dwarf). Dwarfs are tiny spaces of super condensed mass. Our sun will turn into a white dwarf the size of a city and the white dwarf will be 2.5 more massive (mass) than it is know.

Life of a Supernova

It first starts of with a bigger cloud of atoms, and it burns for a much shorter time, only a couple of dozen million years, it will then explode into a supernova.

Nebulas

The mother of suns, they are massive with some parts spanning a couple of light years.