Warning: off topic Science content: "is space cold?"

[fiksal]

all those discussion about "speed" in space made me think of something else

so, I had a long argument some time ago with few people about the popular sci-fi idea that space is "cold".

... feel free to correct my observations, since I am not citing any sources

Cant recall any space-based books, but movies in particular came out with many outrageous and not so outrageous effects of vacuum.

So, being interested in physics, but only being at the highest physics class offered in a two year college, I thought that calling space "cold" is beyond inaccurate. Though that movie with Tom Hanks, was based on a real event, had confused me... could I be wrong?

I went online and started looking for equations, facts, designs of life support systems on the space station, shuttles, space suits and many random physics articles.

My question was – obviously, space is not "cold", but what does happen to the temperature of an object in space.

What I found out was interesting.
So the objects do radiate heat into space. Different materials will radiate more than others.
How fast, and what kind of materials radiate how much - I still didn’t find, so it's a bit of a mystery. Personal I think it must not be much, if the internal temperature of the object is not high.
I also found out, that radiation depends on the reflectivity of the object - shiny metals radiate little, and reflect a lot, whereas darker materials radiate a lot and don’t reflect much... which is nothing new.

Then there's also all that radiation from the sun, which can heat things up.

Another contender, in my mind, was the air particles beyond or at the top layers of the atmosphere. Is it possible that they are extremely cold?

Turns out that, the particles at the outer atmosphere are extremely hot, due to sun's radiation. Though, there is so few of them (thus, low density), that they make no difference to launching/passing by shuttles/rockets.

Sun indeed can heat things up rapidly. Cooling system is big part of the life support on the shuttle / space station / space suit.

So, is space... "hot"? Or more accurately, - do objects in space tend to heat up?

Yes and no.

The key is apparently in how much heat is absorbed and how much heat is released.
If an object / space craft absorbs more than it releases - then it'll heat up. If it absorbs less than releases, then it'll cool down (like on that mission to moon).
The higher the internal temperature, the more energy the object will release.
So, the temperature of the object will change until it'll reach the equilibrium.

So, that makes me think that,
Lets say there’s a space craft. There are panels that absorb sun’s radiation. If they will get knocked off, then craft will heat up.
If an engine will shut off (provided that it is generating a lot of heat), then the space craft will cool down.


So how is that?

[cappedup]

ive been here long enough to know that i am about to be made look foolish.. however, in the absence of anyone else as drunk as me here is my account..

As i understand it, heat is simply joules of energy.. everything that has substance has joules of energy.. i have it, you have it.. we all have joules and they make us hot.. hey, some of us more than others a freezing cold river has joules of energy within it,, not many but they are there, hence geothermic energy techniques can extract that energy and warm up stuff.. it takes a lot of river to pass by before a decent amount of joules has been extracted but the potential is there..

now, space has nothing. actually nothing, there are no molecules, no air, no water, no river, no joules no nothing.. so its pretty cold.. it certainly isnt hot cos there are no joules of energy there.... fall out of a space shuttle in your speedos and you have an acorn of astronomic proportions


have i answered the question? is space cold? of course it is.. it has absolutly nothing in it, certainly not joules of energy.. being close to the sun is irrelevant because you need somthing to 'hold' the heat - probably..

[fiksal]

As i understand it, heat is simply joules of energy.. everything that has substance has joules of energy.. i have it, you have it.. we all have joules and they make us hot.. hey, some of us more than others a freezing cold river has joules of energy within it,, not many but they are there,

yep, you are right

now, space has nothing. actually nothing, there are no molecules, no air, no water, no river, no joules no nothing.. so its pretty cold..

I suppose I wanted to confuse the issue a little bit But you are on the right track.
Temperature is just an internal energy. If I remember my physics correctly it actually correlates to how “fast” the molecules vibrate. Thus the absolute zero is the state where no molecules vibrate.

However, "cold" and "hot" can’t be applied to space... or to be more precise - vacuum.

Aha, but there are gas clouds in space, you say! Yes they are, but the distance between particles is fairly huge. In fact, the vacuum chambers that we can make here on earth might contain more gas molecules than those clouds within the same volume... or so I heard

it certainly isnt hot cos there are no joules of energy there.... fall out of a space shuttle in your speedos and you have an acorn of astronomic proportions

Yep, that is another question, what would kill you and me in space?
Well, I think - it's the difference of pressure. All the gases within our body will want to expand/get out, including air in our lungs. Remember that our body contains gases at 1 atm.

have i answered the question? is space cold? of course it is.. it has absolutly nothing in it, certainly not joules of energy.. being close to the sun is irrelevant because you need somthing to 'hold' the heat - probably..

actually, closer to the sun will mean a lot more sun’s radiation. Certainly it doesn’t matter if there's nothing there. But if you place a thermometer, or a spacecraft - suddenly you'll realize that you are getting to be quite hot

[Zathos]

I guess it really depends on where in space you are.

If you were next to the sun, then the radiated energy would make you nice and toasty.

As you get further away the same radiated energy has dissipated over a larger area and there is less to heat you up.

Once you are far enough away from the sun you get very cold indeed.

Therefore if there is insufficient energy to supply heat space will be cold and as there is much more space than suns, on average space is cold.

[cappedup]

Therefore if there is insufficient energy to supply heat space will be cold and as there is much more space than suns, on average space is cold.

i couldve said that but decided to ramble on a bit...

[Paranoid66]

Glad my delusions havn't been entirely shattered just find the idea of corpsicles particularily amusing for some reason.

Basically in non scientific lingo if your not getting radiated by a sun your freezing your bits off!

[fiksal]

Basically in non scientific lingo if your not getting radiated by a sun your freezing your bits off!

right... though depending on the material, cooling down may happen quite slowly... as I understand.
The temperature won't keep on dropping either. It'll reach an equilibrium.

[Paranoid66]

Basically in non scientific lingo if your not getting radiated by a sun your freezing your bits off!

right... though depending on the material, cooling down may happen quite slowly... as I understand.
The temperature won't keep on dropping either. It'll reach an equilibrium.

Still we are still talking pretty seriously cold here far colder than it would get within planetary atmospheric conditions?

[gaiamark]

So, then, can we all agree that Arthur Dent and Ford Prefect would indeed be able to survive thirty seconds in space by holding their breath after being ejected from a Vogon airlock? [ external image ]

[Sutore]

IIRC, although space is regarded as cold, isn't the problem for us lifeforms that of over-heating if we get caught in space??

Because space is essentially nothing, there is nothing to transfer the heat away from our bodies so it all builds up inside. Hence why spacesuits have a cooling system . . .

Of course, this might be also because there's that big yellow thing pumping out loads of heat as well, which the body cannot get rid of in nothingness.

[pjknibbs]

Thing is, space isn't a perfect vacuum anyway. Even in the depths of interstellar space it's estimated there are 20 or so hydrogen molecules for every cubic metre of space--hardly a vast amount, true, but it's still not as empty as cappedup thinks.

As for temperature, all sorts of weird stuff can happen. For example, the temperature of the sun's surface is 6000C. The temperature of the corona (the sun's atmosphere) is into the millions of degrees, but you can't see it because it's so tenuous and dim compared to the Sun itself. Only during a total solar eclipse does the corona briefly become visible.

[Klyith]

Wow, I'm seriously impressed. A topic that I expected a lot of wrong ideas, but most everyone is more or less right. Woohoo, a victory for science education!


Space, as in vacuum, technically has no temperature. Temperature is defined by motion of matter, and vacuum is absence of matter. Heat is a type of energy, it's nice that everyone here seems clear on that. (It doesn't have to be joules though, that's just the SI energy unit.)

Vacuum is an excellent insulator -- witness vacuum flasks for hot drinks. In true space you can only get rid of heat by radiating it. That's way slower than conduction or convection transfers of heat. Efficiency of radiation is controlled by the difference in temperature between the object and it's surroundings, basic thermodynamics. The speed that you radiate away heat is a power law (I think quadratic), so the greater the difference the faster the rate of loss.

So scientists will often also use "temperature" in relation to vacuum as a shorthand for the point at which an object will be at constant temperature through equilibrium of incoming and outgoing radiation. Similarly, electromagnetic radiation can be assigned a temperature, which equals the temperature at which an object can radiate light of that quanta.

At most human-centric temperatures radiation is very very slow at transferring heat. Remember, absolute zero is only -273°C. So even if a room-temperature object was put in a 0K vacuum, it really is not that much warmer than it's surroundings... Room temperature is pretty cool from a radiation-producing perspective. Even a red-hot iron would keep glowing red for a surprisingly long time in a vacuum.

As said, near a sun space might be quite hot, though it really makes more sense to say the sun is hot. How about in deep deep space, like the voids between galaxies? Out there, the only radiation is the cosmic microwave background (CMB). It's miniscule, the CMB temperature average is 2.728 Kelvin. That's less than three °C above absolute zero. That's pretty cold, and those inter-galactic voids are the vast majority of space, as measured by volume.

So, on average, space itself is cold.
It's just really terrible at making other things cold.


...
Upper atmosphere of earth is very hot, true. But that's counterbalanced by the fact that it's very thin. It has high temperature, but actually a quite low amount of heat energy per unit of volume. If you were put unprotected into that environment, you wouldn't need to worry about being burned by the air. It's very similar to how you can put your hand into a 400° oven and not be hurt by the air. But if you touch a solid object you get burned.

...
As far as spaceships, satellites, and other manmade stuff in space. In spacecraft design the problem is almost never keeping your stuff warm. Most of the time you have plenty of waste heat generated by the operation of your ship/whatever, and the problem is radiating it away. There are a few exceptions... Moving parts that require lubrication often need little heating coils to keep the oil from freezing. Any time you have people on a ship, the energy needed to keep the life support functioning is probably enough to keep the interior warm just by the waste losses.

[Some Strange Man]

Yep. In space, theres not much convection heating. Theres also not a huge amount of conduction heating as objects need to be in contact.

Heat transfer is restricted to radiation.

The hotter you are, the more heat you radiate.

If you radiate more heat than you recieve (like a small hot object might do), then the temperature will drop. How much and how fast depends on the emissivity [normally equivalent to absorbtance].

[cappedup]

Even in the depths of interstellar space it's estimated there are 20 or so hydrogen molecules for every cubic metre of space

you learn something new every day..

[Jericho]

There is a book: Moonfall, about the moon being destroyed by a comet impact and chunks falling to earth. Not a bad book actually. Anyway: As people are fleeing the brand new moonbase, one guy has to take a spacewalk outside the wee transport shuttle (nothing like the Space Shuttle, just a tiny little box with an engine for going from the moon to moon-orbit and back). But he doesn't have a spacesuit. Initially he starts wrapping himself in as many clothes as he can find to protect himself from the cold. Then the pilot points out that he will have the opposite problem, he will feel far too hot. So he goes out in nothing but a g-suit (tight fighting suit worn by pilots to withstand high-g acceleration) and a plastic bag over his head. (He also has a straw in the bag to release the pressure periodically.

He is far from fine when he gets back, as he starts bleeding from every orifice (well, nearly)

[pjknibbs]

That wouldn't be a result of the temperature, though, it would be a result of the near vacuum. Having said that, you could survive for 30 seconds in a hard vacuum without too much trouble--it takes longer than that for the really nasty stuff like your blood boiling.

[Bishop149]

As far as spaceships, satellites, and other manmade stuff in space. In spacecraft design the problem is almost never keeping your stuff warm. Most of the time you have plenty of waste heat generated by the operation of your ship/whatever, and the problem is radiating it away. There are a few exceptions... Moving parts that require lubrication often need little heating coils to keep the oil from freezing. Any time you have people on a ship, the energy needed to keep the life support functioning is probably enough to keep the interior warm just by the waste losses.

Ai, from most of what I've read (fiction and non-fiction) its dumping heat fast enough that becomes the real problem. In the pure speculation that is sci-fi any FTL dive ever developed is likly to require HUGE amounts of energy, thus many sci-fi space craft with such drives are usally depicted by their authors has having very extensive and fancy ways of dissapating heat.

Even if we discount the fairly outlandish pospect of FTL, the energy required to accelerate to a useful % of light speed (you'd need about 99.999% to boost time dilation to the point wher you might get somewhere at that speed and still not have died of old age by the end) in a usefully short period of time whould be astronomical. . . . . and you'd need just as much to slow down.

In other words lots of heat will most likely need to be shed!

[apogee]

nicked from wiki regarding temperature in a vacuum. So it could be wrong!

The temperature of an object is proportional to the average kinetic energy of the molecules in it. In a pure vacuum, there are no molecules. There is nothing to measure the kinetic energy of anything, and temperature is undefined. Were a thermometer to be placed in a vacuum, the reading would be a measurement of the internal temperature of the thermometer, not of the vacuum which surrounds it.

All objects emit black body radiation. Over time, a thermometer in a pure vacuum will radiate away thermal energy, decreasing in temperature indefinitely until it reaches the zero-point energy limit.

In practice, there is no such thing as a pure vacuum since there will always be photons associated with the black body radiation of the walls of the vacuum. A thermometer orbiting the Earth can easily absorb energy from sunlight faster than it can radiate it away. This can lead to a dramatic temperature increase.

A thermometer isolated from solar radiation (in the shade of a larger body, for example) is still exposed to Cosmic microwave background radiation. In this case, the temperature will change until the rate of energy loss and gain are in equilibrium. At this point, the thermometer will have a temperature of 2.725 K, which is often referred to as the temperature of space.

[Paranoid66]

Really interesting stuff. Never really thought about the insulating effect of vacuum. So no instant corpsicles then but a corpse would freeze over time unless it is warmed up by a sun.

Sorry about my lack of physics knowledge. The option was ART or PHYSICS back when I was at school and ART won out as I had some ability with a pencil. Bit annoying really as I have always been fascinated by systems and how everything works.

[MrFrog]

Having read this thread quite thoroughly, I think the fully qualified answer is ;

Yes, Space would keep my beer cold, unless I was next to a star thingy.