Thread: Heat conduction in space

If I touch a hot frying pan in space, will I feel how hot it is?

You sure will -- if you touch it. But in the vacuum of space there is no conduction. The only way a body in space can rid itself of heat is through radiation. If near enough you will feel the radiation the body emits.

Yes. And even if you place your hand near it, you will feel the thermal radiation it emits.

One more thing: space does have a temperature. It's about 4 degrees K -- the background microwave radiation left over (and red-shifted) from the big bang.

There are three ways heat can be transferred: conduction, convection, and radiation.

A body in space in the shadows will cool down, via radiation, to the "ambient" temperature of the space around it, which can vary depending on the amount of radiation present. A body in space in the sun (let's say near the Earth) will heat up from the Sun's radiation to a pretty high temperature -- not sure the exact value.

The surface of the Moon gives a good answer about what you're speculating on, PumaMan; it's a body in space, just like you're looking for, with no air, and with well-documented surface conditions. (I happen to have used the temperature on the surface of the Moon a lot in global warming arguments.) It's in the sidebar of the Wikipedia article on the Moon.

Also, that temperature varies with distance from the Sun, as you'll have realized long ago.

Enjoy.

Originally Posted by Schneibster

about what you're speculating

I wasn't "speculating". I was stating facts of thermodynamics.

You said "not sure of the exact value." That's the exact value, for this distance from the Sun. Convenient.

Be calm; I was just helping out.

You must have been in some bad places. This place is better.

Originally Posted by PumaMan

There are three ways heat can be transferred: conduction, convection, and radiation.

A body in space in the shadows will cool down, via radiation, to the "ambient" temperature of the space around it, which can vary depending on the amount of radiation present. A body in space in the sun (let's say near the Earth) will heat up from the Sun's radiation to a pretty high temperature -- not sure the exact value.

Only if it approximates a black body. If it has a high reflectivity for visible radiation and near black body emission in the IR--it could be quite cold even much closer to the sun than Earth.

Originally Posted by Lynx_Fox

Originally Posted by PumaMan

There are three ways heat can be transferred: conduction, convection, and radiation.

A body in space in the shadows will cool down, via radiation, to the "ambient" temperature of the space around it, which can vary depending on the amount of radiation present. A body in space in the sun (let's say near the Earth) will heat up from the Sun's radiation to a pretty high temperature -- not sure the exact value.

Only if it approximates a black body. If it has a high reflectivity for visible radiation and near black body emission in the IR--it could be quite cold even much closer to the sun than Earth.

Yes, thanks. I was trying not to delve too deep into TD for the OP.

Entertain me with two more answers so that I may fully grasp this.

1. If I take a quick dip into the galactic drink... I mean, if I go into space, without a space suit, would space itself feel cold, even though I am not convecting/conducting my body heat?

2. And then let's say you retrieved my body and put it into a pressurized cabin. I feel like I know the answer to this, but I will ask anyways. Would my body seem cold to touch?

Well, going naked in space isn't your only problem.

If you decompress instantly, you will have massive tissue damage from explosive decompression. You therefore have to decompress slowly. In order to last long enough, then, because it will take longer than the 5 minutes before brain damage sets in, you will have to have an oxygen mask. This will preserve your life long enough so you can suffer maximally.

Even if the decompression is slow, you will still experience broken capillaries all over your exposed tissue. If your eustachian tubes are blocked, or you forget to open your mouth, then your eardrums will perforate. You will fart a lot and for a long time. And belch. But the worst will be your skin, which will first experience popping capillaries everywhere, then be frozen. If you are in the Sun, you will in addition be sunburned at about 20x the normal rate; a minute would be equivalent to a half hour laying on the beach, on each side.

If you were not strong, young, and healthy, you would die. If you were, you'd be blinded and crippled for life. And that's if you didn't die of hypoxia. Not to mention lesser brain damage that didn't take your life.

As for your second question, you'd probably be about as nasty as a drowning victim after several days. You can go read about that elsewhere, for example in police procedural fiction.

There is some information here:
Human Body in a Vacuum
New Scientist Space Blog: How long can you survive in the vacuum of space? - New Scientist
Survival in Space Unprotected Is Possible--Briefly - Scientific American (doesn't make for pleasant reading)
Could You Survive for 14 Seconds in the Vacuum of Space Like in Kubrick’s ’2001′?

Just remember to keep breathing out...

The most important thing is to protect your eyes.

Originally Posted by hencook

Entertain me with two more answers so that I may fully grasp this.

1. If I take a quick dip into the galactic drink... I mean, if I go into space, without a space suit, would space itself feel cold, even though I am not convecting/conducting my body heat?

2. And then let's say you retrieved my body and put it into a pressurized cabin. I feel like I know the answer to this, but I will ask anyways. Would my body seem cold to touch?

Leaving aside the other problems though, you would feel cold on the side of you that was in shadow, as you would be radiating body heat into space and getting no radiation back. How cold I am not sure, as you would not be in thermal contact with any cold air or surface - it would just be pure radiative loss. If the other side of you were exposed to the sun then that side would feel pretty hot I think. But to find out how much we'd need some data on comparative rates of heat loss/gain typically experienced by the human body on Earth, and then do the calculations on the rates of heat loss/gain due to a pure radiative process.