How is space “cold” when it’s a vacuum? Isn’t temperature transferred between mass? If anything, shouldn’t you overheat when in a vacuum, because your body generates heat?
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Yes and yes. Space is cold in the sense that there’s very little to conduct heat, but objects in space are at a serious risk of overheating (because other types of radiation can be transformed into heat) as it can be so difficult to get rid of.
NASA has a page about this and the International Space Station:
– https://science.nasa.gov/science-news/science-at-nasa/2001/ast21mar_1
Space is not a true vacuum, and it’s cold because the few molecules that are there don’t have a lot of energy, which is by definition cold.
That said, you are not wrong in that overheating is a real problem in space. While it might be cold, there’s not enough around to give off heat via convection faster than we build it up, so both space suits and the space station have systems built in to actively shed heat in other ways – like having big metal radiators on the side of the space station that radiate heat away.
Things can be very cold but almost not conduct heat. Touching metal at -100 °C can hurt a lot, and cause serious damage to the skin. Meanwhile, touching plastics is relatively fine; with aerogel, you possibly won’t even notice the cold. That is due to their low thermal conductivity, which your body can overcome. Stuff feels hot or cold when it transfers heat to or from you.
It’s the same with the vacuum of space. Stuff in space (this includes entire planets, astronauts, satellites, asteroids, you name it) cannot conduct heat away in any immediately notable manner.
However, there is another method for things to exchange temperature: light, thermal radiation in particular. Everything emits light, the hotter the more and brighter. You can feel the radiating heat of a campfire even upwind. It’s also what makes very hot objects such as molten steel, incandescent lightbulbs or the sun itself glow brightly. Even your body does so, just at a significantly lower intensity, and effectively all of it as light our eyes cannot see.
It typically takes much longer to radiate heat away as light as to conduct it. Hence your body will heat itself up. Even worse, any sunlight will also add to that. Your own light is just too weak to counter those; it only changes long after you would have boiled to death. Or you stay in the shadow of a planet, in which case stuff will slowly cool down to deep freeze.
Why do you think they have to be mutually exclusive? Space is cold and also you would overheat.
You overheat because space can’t absorb and take that heat from you.
Space is cold because, well, it can’t absorb heat.
So, heat is the transfer of energy, mainly infrared radiation. Radiation is energy that radiates from a source. Here on earth, most radiated heat comes from the sun, with some heat being thermal generated from volcanic activity or other seismic movement.
In space, the radiated heat from the sun does not travel relatively far. While the earth is like 90 million miles from the sun, that’s not very far compared to Jupiter, Saturn, Uranus, Neptune, or the other millions of small ice objects floating around out there.
Now space has lots of stuff in it, but there’s a lot of empty space between the stuff. Heat will transfer either by radiation like with the sun, or through molecular transfer, like with a metal pan handle.
This is why bodies in space might get hot when directly facing a near by star, like how hot murky gets on the day facing side, but without an atmosphere, the dark night facing side releases all the surface heat and quickly becomes ice cold.
Here on earth, or any planet with a thick atmosphere, heat gets trap because of the air molecules acting as an insulator, this is one reason why temperatures get colder as elevation increases, air thins, and insulation qualities decrease, not the only reason, just an example.
Well space lacks that thick insulation atmosphere so heat doesn’t get trapped. This is why if a person floats around in space, the sun’s radiation will burn and boil the unprotected facing side while the side facing away from the sun would be freezing.
>Isn’t temperature transferred between mass?
Through conduction and convection, yes, but not only. There’s also radiation. Everything with heat emits electromagnetic radiation. And there is nothing in our universe with zero heat. Nothing is 0K.
So, everything will emit some heat, nevermind how little. Something is “hot” or “cold” depending on the balance of this emission. If you emit more heat than something next to you, it will receive more heat from you than you receive from it. The effect is that it will gain heat while you lose heat. But as it heats up, it radiates more heat. You cool down and radiate less heat. At some point you reach equal heat, you both radiate as much as you absorb. If you’re isolated, there’s nothing colder than you, that’s it. You’re in equilibrium.
Now to answer the questions you’ve actually asked:
Space is “cold” because without additional source of heat, like sunlight, you will radiate more heat into space that you will absorb. You will absorb some, because even “empty” space isn’t empty. There’s radiation there, the Cosmic Background Radiation. Everywhere, every bit of space. And it’s about 4K, or about -269 C. Pretty cold.
But can you overheat in space? Yes, you can, even without sunlight. Because radiating heat is, while unavoidable, very slow and inefficient compared to conduction and convection. So if you heat up, either internally or by absorbing sunlight, it will he very difficult to get rid of it at the same rate as you gain it.
Technically, “space” isn’t cold, it lacks thermal energy entirely. What we call “space” actually does have some matter in it, but it’s very spread out.
When you put an object in space, it loses thermal energy by radiating it as infrared light. As long as the object is not exposed to sunlight (or any other source of thermal energy) it *will* gradually cool down but it will take hours to days for it to drop below freezing and longer still to reach almost absolute zero.
Space is both very hot and very cold.
If your spacecraft is in the sun, it’s adding a lot of heat to it – at least on the side that is facing the sun. If there’s a part facing the earth and it’s daytime, you also gain heat from the light reflected from the earth.
If part of your spacecraft is facing deep space, you will be radiating energy back out to space and that will make that part cooler.
So you need to manage all of those different heat sources and heat losses, and it gets very complicated in practice. Many craft actually need radiators to get rid of excess heat both from the sun and from the electronics – both the ISS and shuttle had large radiators. Some craft will slowly rotate – usually known as a “barbecue roll” to keep the craft from getting hot on one side and cold on the other. Apollo did this when travelling to the moon.
As Neil deGrasse Tyson said, space isn’t cold, since there is no mass to transfer the heat energy to. However, it would feel slightly cold to the body, since your body would slowly radiate heat away. There are, however, areas of space filled with gas coulds that would feel as cold as that guy said in the infamous tweet that just popped up. He did a google search and didn’t check the source.
There are a few sides to this. Heat isn’t just transferred through contact. In fact, there are 3 main methods of heat transfer. But first, what do we mean by “heat” or “temperature”?
Really, temperature is just how quickly all the particles in something are vibrating, i.e. the how much the tiny stuff that makes up big stuff is wobbling. Heat is just these wobbles getting passed on to something else.
This transfer can happen through conduction, where neighbouring bits of stuff make each other wobble. If you heat one end of a metal bar, the atoms in that end vibrate quicker. They pass these vibrations onto their neighbours, who also vibrate quicker. So, the heat gets conducted along the bar. Or, we could put two different objects of different temperatures together, and the heat conducts from one to the other.
The next method is through convection. Rather than the heat being passed on between neighbours, the different particles actually move about as they vibrate. In a pot of water, the heated molecules at the bottom move up to the top, and let other particles take their place at the bottom to get heated there. Or, you could think of a mascot at a game moving around in the crowd and hyping them up.
The third method is radiation. Everything that has heat energy is giving off radiation: light which is (partly) beyond the visible spectrum. Infrared light shoots off of stuff, hits other stuff, and warms it up. That’s why it feels so hot next to a fire. The glowing hot coals/logs are firing infrared radiation at you, making your face get hot quickly.
In space, we can’t transfer through convection or conduction because there isn’t any contact. However we can still emit radiation. But, as you say, heat can still get trapped in things. So why do we say space is cold?
Well, it’s really because the stuff *in* space is cold. Space isn’t a perfect vacuum. And the particles in space are wobbling with some temperature. It turns out that the average temperature of the stuff in space is something like 3K, or -270°C. (If you want to work that out in freedom units, feel free!) That’s pretty darn cold!
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