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

It’s not absolute zero, but I get your point.

It’s a question of mass.

There’s three ways to transfer heat.

There’s conduction, where two things are transferring heat by physically touching each other. This is the fastest way of transferring heat. For example, an electric stove heating element is physically touching the pot.

There’s convection, where two things are transferring heat by physically touching a medium that moves between them. For example, if you’re baking something in your oven the heating elements are heating up the air which circulates inside the oven where the air touches your food and heat it up. This isn’t quite as fast as conduction, but it’s still pretty good.

The last is radiation. Every object releases light based on its temperature (this is called black body radiation and it’s how infrared thermometers work and how we can tell what temperature stars are). This is not a very efficient method of heat dispersion, and it gets less efficient the larger an object is because the ratio of mass to surface area results in a smaller and smaller percent of the energy being able to radiate out because the surface area is smaller compared to the mass.

So to bring this back to your question: There’s no stuff in space, relatively speaking. There’s only a couple of *atoms* per cubic meter in deep space. No stuff means no conduction or convection, or at least not enough to matter. That leaves radiation. Which is how the sun heats the earth.

>how can, for example, a spaceship keep a confortable temperature in the inside if outside there is such a massive temperature drop?

Fun fact: We have to use heaters! Spaceships are designed to radiate out more heat than the stuff inside generates (people and equipment) and the supplement that heat loss with heaters. We do this because vacuum is an incredible insulator for the reasons stated above (the best insulated cups and coolers, like Yeti, are insulated by nothing at all – by vacuum.) so it’s safer to run cold because if you ran hot you’d cook everything inside.