Like i understand there isn’t a lot of things for the heat from Stars to bounce off of but what causes Space itself to be cold? Is it naturally always cold and if so why?
In: Planetary Science
You have a backwards view in general.
Everything is cold. Absolute 0 infact unless it has a reason (energy input) to be warmer than that. Space is cold because not enough energy has been added to it to make it warmer – that’s the natural state of everything.
You answered it, there is essentially nothing at all to transfer heat. Rather, the gas and dust particles are too far apart. But to a point where there is nothing at all.
Basically everything is cold unless it’s heated. Most heat comes from the movement of atomic and sub-atomic particles, which most of space is notoriously short of because it’s a near perfect vacuum.
Technically speaking, space is actually neither hot nor cold.
In the parts of space where there is literally nothing, there is nothing to *be* hot or cold. Words like “hot” and “cold” talk about the motion of molecules and atoms. If they’re moving very fast, they’re hot. If they’re moving very slow, they’re cold.
Space has no atoms in it to be hot or cold.
In direct sunlight, things in space can actually get hot very fast. This is because the radiation from the sun heats up molecules it touches.
But when you aren’t in direct sunlight, there’s nothing to hold onto heat or bounce it back to you. You may lose heat very fast via your own form of radiation, and there’s nothing to trap it close to you.
So space gets a reputation for being cold, when it’s actually *neither* hot nor cold.
Well it is and it isn’t. We instinctually understand cold as the sensation of when heat moves from our body to something else. In a vacuum with no sun, there’s no air to warm up or anything to insulate us, warm things in dark space will radiate away all of their energy. However in a solar system the suns energy heats things up. Without air, all that energy is directly absorbed by things in space. That is why the moon is +200°f on the sun side and -200°f on the dark side.
So it’s not that space is “cold” or “hot” it’s more that space isn’t anything. So we lose all our heat and intuitively understand it as cold.
Heat comes from stuff moving around a lot. Space is a void, no stuff exists in most of space, hence, no little things (molecules) moving fast. So any heat that you put into space dissipates super fast, becoming cold.
Cold is the default state in a vacuum. Add matter and agitate the molecules, and now you can have heat.
Stick a hot rock in a vacuum chamber with a thermometer a foot from it. It is radiating some heat, so the thermometer may be slightly affected by that. The thermometer will not register convective heat because there’s nothing convect through, no air to warm so that the thermometer is exposed to the warmth. There’s no mass between the rock and thermometer to hold any heat, so it’s cold in that area.
Now we go to space, which is a pretty good vacuum. Tiny particles in it are being warmed by the Sun, but you’re not going to feel their heat, same as the rock. But you are getting pretty hot if you are in the Sun’s rays.
Heat is caused by energy, in absensce of energy there’s no heat, the void of space is so big that even if you can look the sun directly it’s energy won’t produce enough heat because there is not atmosphere to retain that energy, that doesn’t mean your skin can’t be burn due to UV rays.
Heat is not a substance, it is the motion of matter. Take the same coin, if its pieces are jiggling around very fast, it is hot, if they are sluggish, it is cold. Empty space is not hot or cold, the concept doesn’t apply; it is not made of matter.
Now, there is a thing called radiant heat, which is actually a way to move heat around, not heat itself. The pieces of hot things jiggling around smash into each other a lot, and when they do it it makes them glow just a little bit. That glow is infrared light, which bleeds off a little bit of their speed, which makes the hot thing colder. If that light hits another thing, the light will heat the other thing up, which is why it’s called radiant heat.
If a thing is alone in space shaded from sunlight, it shoots off its infrared glow, becoming colder, without getting warmed by anything else’s radiant heat. That is why we say it is cold in space. Not because space is cold, but because things get colder alone in space.
But space is not cold.
kinda contradicting some of the answers here, but not really, because it’s important to get the concept right.
strictly speaking, “space” isn’t cold, it’s hot. when we say something is “hot” or “cold” we’re talking about how fast particles are moving. and particles in space are *real* fast. the problem is, space is very very empty. so there’s very few little of these particles.
it’s important to distinguish these concepts because it has important ramifications – because space isn’t really “cold” it’s actually a challenge to get rid of excess heat when necessary – the ISS has these large things that jut out into space that are *not* solar panels (though they have them), they are just part of the cooling system, angled away from the sun, just to try maximize heat just radiating away (on earth, heat can convect away through the interaction of hold particles and cold particles, in space convection isn’t possible you can only radiate, which is much slower)
edit: to the folks saying that cold is simply the absence of heat, or that cold is the default state of a vacuum, that’s wrong. as i mention, what we conceive of as “cold” is simply lower on the spectrum of particles moving around. a pure vacuum has almost no concept of cold because there’s nothing to actually move around. if you were somehow put into a vacuum while alive, you wouldn’t feel cold, at least for a while – there’s nothing to take heat away from you in that vacuum the way air molecules could. in fact, if you were in the vacuum of space but with a clear line of sight to the sun, you would get really hot because the sun would be imparting way more energy to you via radiation than you would be losing heat via radiation.
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