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

If you have a bonfire inside a bedroom, the average temperature of the bedroom is quite high. If you have the same bonfire in a stadium, the average temperature of the stadium is much lower, because there is a much higher amount of non-bonfire (proportionally). In space, there is insanely a looot more non-bonfire (temperature of the void is absolute zero, to simplify it), so even if there are things as hot as stars, the average temperature is very low. However, vacuum is also not a good heat conductor: no direct contact or convection, so the only way to transmit heat is radiation, which for something with the temperature of a spaceship is a very slow process. But for something the temperature of a star, the amount of heat transmitted is much higher, therefore the Sun heats the Earth.