What is a light year?
Light is the fastest thing we know of. For example light can travel about 7 times around the Earth in one second – that is 186,000 miles per second. A light year is the distance that light can travel in one year – about 5,880,000,000,000 miles.
How big is the Milky Way?
It is about 150,000 light years across.
How far is the nearest star?
It is about 4.3 light years away. That means that even if you were travelling at the speed of light it would take 4.3 years to reach it. The other stars and galaxies are even further away. Some are billions of light years away.