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Comment by teekert | Hacker News Reader

Lay people associate space with cold because nearly every scifi movie has people freezing over in seconds when exposed to the vacuum of space (insert Picard face-palm gif).

Even The Expanse, even them! Although they are otherwise so realistic, that I have to say I started doubting myself a bit. I wonder what would really would happen and how fast...

People even complained that Leia did not freeze over (in stead of complaining about her sudden use of the force where previously she did not show any such talents.)

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Well empty space has a temperature of roughly -270c...so that's pretty cold.

But I think what people/movies don't understand is that there's almost no conductive thermal transfer going on, because there's not much matter to do it. It's all radiation, which is why heat is a much bigger problem, because you can only radiate heat away, you can't conduct it. And whatever you use to radiate heat away can also potentially receive radiation from things like the Sun, making your craft even hotter.

> Well empty space has a temperature of roughly -270c...so that's pretty cold.

What is this “empty space” you speak of? Genuinely empty space is empty and does not have a clearly defined temperature. If you are in space in our universe, very far from everything else, then the temperature of the cosmic microwave background is what matters, and that’s a few K. If you’re in our solar system in an orbit near Earth, the radiation field is wildly far from any sort of thermal equilibrium, and the steady state temperature of a passive black body will depend strongly on whether it’s in the Earth’s shadow, and it’s a lot hotter than a few K when exposed to sunlight.

You know exactly what the term "empty space" means and of course it does not mean empty in absolute terms.

Wouldn't a body essentially freeze dry as a wet being exposed to vacuum? I.e. the temperature of the space is still irrelevant and the cooling comes from vaporization.

Any exposed fluids (mostly saliva) technically boils but you can think of it as evaporation to avoid layperson associations with heat -- it's all about low pressure, not about heat in layperson terms.

Whether you freeze or not depends on whether you're in the sun or not. Spacesuits are white to reflect as much light as feasible mostly to keep the astronauts from cooking. For example, surface of the moon can heat to 120° C / 250° Fahrenheit / 400 K.

Over time I'm sure all the liquids will manage to escape. Here's what happens to blood not contained by blood vessels and skin: https://www.youtube.com/watch?v=jU3MOLqA3WA

I'm reading through the Expanse books and a passage that I read after seeing your comment jumped out at me. It's a quote from Havelock:

"As a boy living planetside, he had always thought of space as cold. And while that was technically true, mostly it was a vacuum. And so a ship, mostly, was a thermos. The heat from their bodies and systems would bleed into the void off over years and decades of it had the chance."

So at least the books got it right!

It’s not that dumb- if a human gets exposed to space the water in their exposed tissues will boil off, leading to evaporative cooling. In a vacuum, evaporative cooling can get you ~arbitrarily cold, as long as you’re giving up enough fluids. I don’t know whether you freeze over or dry out first, but I’m sure someone at NASA has done the math.

2001 did it pretty close to right, but watch it with normies and they'll laugh at it because it doesn't meet their expectations.

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