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February 8, 2007

David: Ask Dr. Science

“No, it actually isn’t cold in space,” the astronaut lectured to his companion. “Temperature is a property of mass, the amount of chaotic kinetic energy possessed by the molecules of a substance. Deep space has no mass. Ergo, no temperature. Instead, it is a heat sink, drawing heat away as infrared radiation.”

“Shut up, please.”

“I’m just saying if you want to complain, get the technicalities right.”

“Okay, so we’re going to freeze to death not because space is cold, but because it sucks.”

“Heavens, no. This capsule is far too small. We’ll run out of oxygen long before that.”

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Comments

Super good. "Heavens no" hahaha

Posted by: kasac at February 8, 2007 2:49 PM · Permalink

Feh, Deep Space isn't even close to a perfect vacuum.

Posted by: Jeff R. at February 8, 2007 3:24 PM · Permalink

Close enough for the story, and for a guy who has to keep talking or he'll go bibbledy.

Once you're in a place where mass density is so low that radiative heating/cooling becomes dominant by orders of magnitude, discussing the temperature of that place becomes pretty pointless.

Besides, I didn't have room to put in "almost."

Posted by: David at February 8, 2007 5:04 PM · Permalink

Geekfight!

Posted by: Stacy at February 8, 2007 5:30 PM · Permalink

Even if you're just talking radiative, there's still the temperature of the Cosmic Microwave Background Radiation to consider...

Although that takes even more words than 'almost' to deal with...

Posted by: Jeff R. at February 8, 2007 6:34 PM · Permalink

"Geekfight!"

Hehe.

Posted by: Jim Parkinson at February 8, 2007 7:36 PM · Permalink

Radiation can't have a temperature. It can transfer energy, but that's not the only criterion in the definition of temperature. Temperature requires mass, in a strict scientific sense.

If you stick a thermometer out the window of the space shuttle, it's like you're dividing by zero. Undefined. (Except that it's still close enough to the atmosphere to...bah, it's complicated.)

Posted by: David at February 8, 2007 7:57 PM · Permalink

Again, there's mass out there. And energy, which is the same thing. Not to mention the stew of virtual particle/anti-particle pairs everywhere. And it's all still hotted up from the big bang to a balmy 2.75 Kelvin in the shade; downright sweltering if your physiogonomy happens to be comprised of Bose-Einstein condensates...

Posted by: Jeff R. at February 8, 2007 8:29 PM · Permalink

So, Timmy, do you like gladiator movies?

Posted by: Jim Parkinson at February 8, 2007 8:41 PM · Permalink

*falls down laughing at Jim*

Posted by: Stacy at February 8, 2007 9:03 PM · Permalink

Not enough mass to matter, compared to radiative effects, on a practical human scale. It's a million particles per cubic meter or so, mostly hydrogen, compared to 6.022x10^23 particles per 22.4 Liters for air at atmospheric pressure.

There's almost nothing there to conduct heat through. For practical purposes, it doesn't happen. It's negligible, so we neglect it.

Also, energy transferring from one object to another without use of an intervening medium is a completely different mechanism than conduction through a medium. "Energy = mass" doesn't mean anything in this context. You can't conduct heat through a photon stream. And virtual particles don't last long enough to matter, except near a black hole, kinda by definition.

But yeah, if you measure on a big enough scale, what we see as vacuum can be considered a gas. It's just that that's generally irrelevant for heat transfer.

Posted by: David at February 8, 2007 9:34 PM · Permalink