Why is space cold if there’s no matter in it?
In: Physics
Basically there isn’t much to heat up because it is empty and any heat will fly off into empty space.
Heat is how much atoms are vibrating. Fast vibrations are hot and slow vibrations are cold. No movement is absolute zero. Space doesn’t have many atoms because it is mostly empty and the ones that are about have very slow vibrations and aren’t moving about.
Because there isn’t much atoms about in space the heat from the sun doesn’t have much to heat up, so it stays cold.
The atoms that are about in space will get heated up by the sun but will quickly cool back down without much chance of passing that heat onto something else nearby (unlike on earth where there are lots of atoms for heat to “move” into).
In space the heat kind of flies off into empty space by radiation, which is a slow process where the vibrating energy kind of gets released with nothing to cling to.
The vacuum of space itself isn’t really cold, it’s empty. The things *in* the vacuum tend to be cold, because they are usually in space for long enough that they have radiated all of their heat away and aren’t getting much new energy. You tend to gain or lose heat in two different ways – through direct contact or through radiation. In space, you can’t gain or lose heat through direct contact most of the time, so you’re well insulated in that regard, but you can gain and lose heat by radiation. Since you radiate energy away faster than you gain it (unless you’re close to the sun), you will eventually cool down, but it’s nowhere near as fast as portrayed in movies.
In direct sunlight you might actually never freeze, since you can gain energy a lot quicker than you would radiate it, but again that depends on your distance from it. If something is blocking the sunlight, you’ll freeze in around 12-24 hours from radiating your heat away.
Cold is just the lack of heat. They aren’t two opposing forces; heat is the force, cold is what you get when heat is missing.
Without anything to warm it up (the sun, hot molten planetary core, a radiator), everything gets cold. That’s the natural way of things. Areas completely devoid of any sources of heat whatsoever sit at absolute zero.
Heat travels through particles (picture warm particles “vibrating” with warmth, so much so that they make their close neighbours vibrate too, which makes *their* neighbours vibrate). This means you need a lot of particles at a reasonable density in order for things to be warmer.
Space has so few particles that the heat that exists in the universe has no way to travel. The few particles that do exist out in the void of space are very spread out, and unable to transmit warmth to their neighbours.
Space is basically a vaccuum. In space you can only lose energy to radiation. Since nothing heats you up (unless if you are close to and in direct sight of a star) you will continually lose your thermal energy (heat) until you have no energy left. This is all it takes for anything in space to reach extremely low temperatures around 2.7 degrees kelvin.
Space itself contains a few atoms per square meter that has undergone the same effect which is why space is said to be 2.7 kelvin. But these few atoms are not enough to cool you down when you are in space so don’t expect space to cool you down like cold air. You will slowly lose your energy to radiation. Practically no energy is lost because of being in contact with these few cold atoms.
It doesn’t matter. There’s just not much heat in it either and that’s what ‘cold’ means.
Cold is not matter or energy. If you go out in space, the only ‘heat’ you’ll get is extremely weak – coming from faint light from stars mostly unless you get too close to one.
I would say the chance of two specific things hitting anything is very very small. The chance of once audition thing hitting anything is small, and the chance of anything hitting something else is common. If you’re traveling through space, you are far more likely to die from starvation or dehydration than something colliding with you.
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