if the universe is so big and so cold (close to the absolute 0) how can it be that inside it there are small (compared to it) things like stars and planets that are way hotter than its temperature? how can Earth climate get hotter and hotter if it’s surrounded by such a cold environment?

Question

if everything that is surrounding us and everything else (the sun, other stars, planets etc) is cold to the point of beeing at absolute zero, how can things be at such a higher temperature? how can, for example, a spaceship keep a confortable temperature in the inside if outside there is such a massive temperature drop?

sorry for the many questions, but they all are part of the same big one 😀

In: 10

Answer 1

The initial energy comes from work done by the gravitational field. Widely separated particles fall towards each other, and when they finally collide their kinetic energy becomes heat. Every part of a star initially falls on top of the rest, increasing the strength of the field, so it has a snowball effect. Eventually it contracts under its own weight enough to start a nuclear reaction.