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

Two main reasons. The first is that a vacuum makes for an extremely effective insulator. The near nothingness in outer space makes it hard for thermal energy (i.e., heat) to radiate away quickly. It still does, but it takes a long time. The second reason is that stars (and even planets) produce their own heat – stars through nuclear fusion and planets through radioactivity (and they have lots of residual heat from formation and are heated by the energy from their stars too). Regarding spaceships – they are well insulated.

On Earth, where we are surrounded by air or water, distribution of heat happens easily as molecules of some hot thing come into contact with lots of air or water molecules constantly, allowing transfer of kinetic energy from the more energetic thing (the hot thing) to the less energetic air or water. Even so, isolated air is a pretty effective insulator too as long as it’s unable to mix with the air all around us. It’s how most insulation (everything from fiberglass to feathers) work – they trap the air keeping it from mixing with the atmosphere.