[NRA]Outer Space Temps [NRA]

Let'sgoflying!

Let'sgoflying!

Touchdown! Greaser!
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Dave Taylor
NRA= not really aviation

I am having a hard time coming to grips with what the temp is above the tropopause and beyond...
Wiki says

"The few particles of gas in this area can reach 2,500°C (4500°F) during the day."
and
" A normal thermometer would read significantly below 0°C."

So, is it hot or cold out there?

It seems like a riddle; "What feels cold to the touch, but is really as hot as blazes?!"
 
Now, I'm really rusty on this, but....

Heat is energy.
A thermometer measures energy in that energy transfer will make a metal (mercury) or liquid (alchohol) expand/contract linearly over the accurate range of the thermometer.

Way up there, you have very few particles (and I assume they mean molecules) of gas. Each individual molecule may be very warm, but the energy per molegule is very low. So, unless you've got a lot of them, you don't have a lot of energy to affect a thermometer.

Analogy: fourth of july sparklers - they send off blazing pieces of magnesium, but you can get hit by the sparks and not be burned, because each individual piece is teeny tiny, so the net energy per piece is low. Grab the burning sparkler, however, and you're gonna get burnt badly.

Proof: Boyles law and the Kinetic Theory of Gases, both of which basically interrelate temperature, pressure, and volume. So, a certain volume of gas at higher pressures will have a higher temperature, and at lower pressures (in the example above) the overall system will have a lower temperature.
 
atmprofile.gif


The above is the dry adiabatic lapse rate (you know, the -1°C per 1000 ft) to show how a packet of dry air cools as it is lifted. For reasons mentioned about, once you get past the mesopause, the temp increases due to an increase in energy but the molecules are so far apart (near vacuum) that you don't fry.
 
Let'sgoflying! said:
So, is it hot or cold out there?"
Click to expand...

Yes.

Thermometers are designed to measure the temperature of the substance surrounding them - they use convection to transfer the ambient heat into the body of the thermometer. There's no substance to speak of out in space, so the thermometer doesn't work. That doesn't prevent the thermometer in space from giving you a reading, however. If it's in the shade it'll loose heat through radiation and give you a cold reading. If it's in the sunlight it'll absorb radiation and give you a high reading. The thermometer really should be flagged. :D

In chemistry and physics, temperature is a measure of the mean speed of the molecules (at temperatures where you have molecules). If the few molecules that do exist in the vacuum of space happen to be whizzing around really fast, then they're consisdered to have a high temperature. Beats me how one measures that, though.

Regards,
Joe
 
Joe B said:
(at temperatures where you have molecules)
Click to expand...
What do you mean by that statement?

There are molecules in space, those molecules may have motion which is then a measure of their 'heat'. The only time molecules are not in motion is at absolute zero. Then they have no 'heat' but they still exist.
 
If I could step outside the spacecraft with my jeans and t shirt on, would I bake off, or would I rush back in for my jacket?
 
Dave, you'd explode, and your blood would boil.
 
PhantomCougar said:
atmprofile.gif


The above is the dry adiabatic lapse rate (you know, the -1°C per 1000 ft) to show how a packet of dry air cools as it is lifted. For reasons mentioned about, once you get past the mesopause, the temp increases due to an increase in energy but the molecules are so far apart (near vacuum) that you don't fry.
Click to expand...

And we all know that the Menopause is MUCH hotter than this :rofl:
 
joeb said:
(at temperatures where you have molecules)
Click to expand...

smigaldi said:
What do you mean by that statement?
Click to expand...

When temperatures get high enough molecules and atoms fall apart. I'm not sure how one defines or measures temperatures under those conditions - plasma physics is way above my pay grade.

Regards,
Joe

PS: Kevin, great observation!
 
smigaldi said:
What do you mean by that statement?

There are molecules in space, those molecules may have motion which is then a measure of their 'heat'. The only time molecules are not in motion is at absolute zero. Then they have no 'heat' but they still exist.
Click to expand...

AFaIK, when things get "hot" enough you have nothing but Quarks.
 
OK I just read a story about the French parachutist jumping from the limits of the atmosphere. They say at a certain point, and thence into space, it just feels cold and you need heated gear, not cooling equipment.

I can live with some theoretical aspects saying 'there is extreme heat, but you just can't feel it'.
 
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