A light year is a distance.
It's the distance that light travels in a year, through vacuum.
The distance is about 5.875 trillion miles.
The nearest star outside our solar system is about 4.2 light years from us.
Sorry to have rambled on for so long.
Hot air rises<span> because when you </span>heat air<span> (or any other gas for that matter), it expands. When the </span>air<span> expands, it becomes less dense than the </span>air<span>around it. The less dense </span>hot air<span> then floats in the more dense cold </span>air<span> much like wood floats on water because wood is less dense than water.</span>
It produces oceanic crust,
