cross-posted from: https://feddit.uk/post/44126927
Goldilocks
Space isn't cold. It isn't hot either.
this post was submitted on 12 Feb 2026
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I forget sometimes that while space isvery cold, it's also an incredible insulator.
I know its memes, but the astronaut tim peake discussed the space suits on No Such Thing As A Fish where he said that the whole get-up is like 16+ layers thick, and the only heating inside is for your fingertips, so you dont lose fine motor function. He said you can be sitting working on a panel outside the station, with one hand facing the sun and one hand facing the shade, and the delta-T of your two hands could be something like 500°C.
Maaaaadness! (It's been a while since I listened to this episode, my memory of numbers could be skewed.)
What is a "delta-T?"
Difference in temperature.
a massive plasma cannon.
The Sun is a mass of incandescent gas, A giant nuclear furnace.
Where hydrogen is built into helium at a temperature of millions of degrees 🎵
Goldilocks space is like "my breath immediately turns solid in the shade and my body is turning to charcoal in the direct sunlight"
You need a giant buffer of atmosphere to help average the temperature a bit. Maybe some kind of large rock with a dense atmosphere?
That or a giant space turtle with elephants holding a flatten rock on it's back.
But what's holding up the elephants?
More elephants, obviously
WRONG! It is turtles actually. It's elephants alternating with turtles (and then every tenth level is capybaras) all the way down.
I stand corrected.
If you go that way you gotta have at least 8 colors.
A strong thaumic field slows down the sunlight too. Doesn't change the heat but it's nice to see sunrise pour across the landscape like honey
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If that blows your mind then think about this: As the universe expanded after the Big Bang, it cooled from unimaginably high temperatures. In principle, this suggest that there could have been a very short window much later, tens of millions of years after the Big Bang, when the background temperature of the entire universe was capable of sustaining life everywhere. Some physicists have suggested this might have created a brief, universe-wide “habitable epoch,” though this remains theoretical.
I'm not an expert, so this is probably not a muture understanding, but it's cool to imagine a universe where life was incredibly abundant.
I'm skeptical of this. Life doesn't just need a certain temperature, it needs to convert lower entropy energy to higher entropy. A uniform environment temperature does not provide any usable energy. You would still need a star or some other energy source.
but it’s cool to imagine a universe where life was incredibly abundant
There was probably nothing but helium, hydrogen and a tiny bit of lithium at that period.
Those are some of the best elements though.
They surely are popular...
Top 3 probably
Yeah, season 8 of helium is just chef's kiss.
Well, "life as we know it". But for all we know energy rather than matter-based beings could have existed more readily back then, and perhaps struggle to exist now under lower density conditions. Thereby making that earlier era more habitable for their type of life, even as our current era is more habitable for our own type.
More weird to me is that, at some point before the first stars, the entire universe glowed through the entire rainbow, so there is a moment when, were you to travel back in time, the entire universe would glow blindingly green.
It probably would never appear green, due to the black-body radiation distribution. When the peak is at green, it just looks like white to us. Our sun is kinda a "green" star due to this
But it would go from blue to white to red. Similar colour progression that we can find in the distribution of stars
Indeed! Good point! For some reason, I was under the impression that the CMB was monochromatic (corresponding to a red shifted equivalent of the precise energy of W and Z boson annihilation to produce photons). Thanks!!
Interesting theory, I'd never heard of it before. All of the sudden, "a long time ago, in a galaxy far, far away", actually seems plausible (although this theory looks like it came well after SW in 2014).
The actual paper about it: https://lweb.cfa.harvard.edu/~loeb/habitable.pdf
This is not completely correct though. It is our atmosphere/albedo/geological and natural processes that help maintain consistently livable temperatures, not just living in the habitable zone. No atmosphere? We'd be like the Moon, where it is too hot in sunlight and too cold in shade despite being similarly far from the sun as Earth.
Also its not true that space is "very very cold".
If you are in space wearing space suite that doesn't radiate heat properly, you could die from the excessive heat. Once dead your body stops producing heat and the existing heat eventually radiate away and your body freeze.
Space is neither hot or cold because these are property of matter. Since space has very little atoms, it technically has no temperature.
Can't ignore bosons; photon wavelength is a measure of temperature too.
Space has a temperature, which is based on the average of incoming radiation through that space; i.e. the thermal equilibrium to emit as much energy as is absorbed by a theoretical perfectly thermally conductive black body at that point in space.
Based off CMB radiation, space on average is a little over 2.7 kelvin. It'll be hotter near stars, but the void dwarfs matter on a cosmic scale
TIL.
I guess it depends on definition of the word "temperature".
I was referring to the classical definition
In classical thermodynamics and kinetic theory, temperature reflects the average kinetic energy of the particles in a system, providing a quantitative measure of how energy is distributed among microscopic degrees of freedom.
71763 notes
what this mean?
It's analogous to a combined count of how many people have commented on the post, or shared it (or "reblogged", to use the Tumblr term). It might also include likes? I only use Tumblr occasionally so I'm not sure.
I don't know why Tumblr counts things like this. I sort of like it though — it makes it feel like a distinct place. Tumblr hasn't escaped enshittification, but it makes me happy that it still exists as a little pocket of weirdos
Vacuum doesn't have a temperature~
But you will if you sit in a vacuum for a while without a radiation source nearby, and it will be quite low.
Are you dissipating heat in a vacuum, though? Pressure shenanigans aside, would someone's body heat slowly, continually build up, or would they freeze?
If you could somehow prevent yourself from dying due to lack of pressure, without blocking heat, you would radiate about 650W more than you generate.
That's using the Stefan Boltzmann law, at normal body temp, perfect blackbody and 1.5m2 of skin. (~ 750 Watt) And then assuming 2000kcal a day (~100W)
You'd cool down pretty quickly.
So how long do I have? Also, if you guys could hurry with the answer...?
RIP
I can't really find a good number for how cold you can get and not die, so let's say 20 degrees. That gives 16 degrees to lose.
Meat has a specific heat of about 3.5kJ per kilo per degree, so say you weigh 70kg, that's about 4 million joules to lose before you die.
At 650 joules per second, you've got slightly over 10 minutes. Of course, shivering will burn more calories and stuff, and the panic of impending death will likely stretch it a few more.
I didn't include clothes, because then the maths would make me cry.
Your skin isn't at core temp tho, so the loss rate should be lower I think
At that point, you'll have to calculate the heat transport of the human body, and answer questions like "how long can a person live with frozen skin" and other fun questions I'm not equipped to answer.
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Heat buildup is actually a problem in space, yeah. You need heat sinks on long term space flights.
You constantly radiate heat. The warmer you are, the faster you radiate it away. In space this is the primary way you lose heat.
In your living room you are constantly bombarded by radiated heat from all the objects that surround you, even if they're just at room temperature, which lessens the effect. In space, not so much.
Someone who knows better might chime in, but as far as I know the trope of rapidly freezing out in space is exaggerated. You would definitely freeze eventually, but perhaps not as dramatically fast as portrayed in The Guardians of The Galaxy for example.
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The dark side of your body in space is freezing cold while the light side gets hot. You really need to rotate to get that even crispy layer.
Not anymore, there's a blanket
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