It’s very odd to think of something extremely hot but with almost no density, and therefore very little heat transfer.
kadoban · 1h ago
Closer to home you can get similar things when you grind metals for instance. The sparks are at extremely high temperatures, but won't typically start fires or cause burns (it depends) because they're just too small to impart much actual energy to anything they touch.
You only get fire risks when the things they touch are themselves tiny (like dust), so they're unable to absorb and spread the heat.
A similar thing happens when you bake with tinfoil. The foil will be at like 350 F, but you can still touch it basically immediately if you're willing to gamble that nothing with thermal mass is stuck to it where you can't see. It just doesn't have enough thermal mass on its own to burn you, but if there's a good-sized glob of cheese or water or something on the other side you can really be in for a nasty surprise.
chasil · 1h ago
I wonder if actual tin foil would behave differently from the aluminum foil that we are all now using.
Tin foil and aluminum foil do have generally different properties. For instance, tin foil can disrupt mind control and aluminum foil can't, and corrosion effects are likely at least different. But any thin metal foil isn't going to be able to hold much heat, because there's just not that much material.
kosievdmerwe · 39m ago
The other thing that helps you is that you're made mostly of water, which is one of the substances with the highest heat capacity. So it's hard to heat up or cool.
jordanb · 2h ago
That's actually most of space. Space is a very hot environment, especially where we are so close to the sun. Think about it. When you stand outside in the sun you heat up. All that heat is coming from the sun. But a lot of it was filtered by the atmosphere, so if you're in space near earth it will be hotter than standing at the equator on a sunny day, in terms of radiation.
Then there's the fact that heat is very difficult to get rid of when in space. The ISS's radiators are much bigger than its solar panels. If you wanted to have a very-long eva spacesuit you'd have to have radiators much bigger than your body hanging off of it. Short evas are handled by starting the eva with cold liquids in the suit and letting them heat up.
All of the mockups of starships going to Mars mostly fail to represent where they're going to put the radiators to get rid of all the excess heat.
hwillis · 38m ago
> If you wanted to have a very-long eva spacesuit you'd have to have radiators much bigger than your body hanging off of it.
I was curious about this! The Extravehicular Mobility Units on the ISS have 8 hours of life support running on 1.42 kg of LiOH. That releases ~2 kJ per gram used, so .092 watts.
The 390 Wh battery puts out an average of 50 watts.
And the human is putting out at minimum 100 watts with bursts of 200+.
Long term it's probably reasonable to need at least 200 watts of heat rejection. That's about a square meter of most radiator, but it needs to be facing away from the station. You could put zones on the front/back and swap them depending on direction, as long as you aren't inside an enclosed but evacuated area, like between the Hubble and the Shuttle. The human body has a surface area of roughly 2 m^2 so its definitely not enough to handle it- half of that area is on your arms or between your legs and will just be radiating onto itself.
It's also not very feasible to have a sail-sized radiator floating around you. You'd definitely need a more effective radiator- something that absorbs all your heat and glows red hot to dump all that energy.
pomian · 1h ago
Reminds me of the book Saturn Run, by John Sanford - which has a lot of effort put into the technology and radiation of heat in their space ship. Fun science fiction book.
thom · 1h ago
See also: "let's build data centres in space, it's cold up there!"
hwillis · 53m ago
Per wiki: radiators reject 100-350 watts per m^2 and weigh ~12 kg per m^2. Not unlikely you would need 10x as much radiator as server. You need about as much area for radiators as you do for solar panels, but radiators are much heavier.
That also makes nuclear totally infeasible- since turbines are inefficient you'd need 2.5x as many radiators to reject waste heat. Solar would be much lighter.
Nuclear power is very feasible in space. Perhaps you're overlooking that radiated power scales with the quartic of absolute temperature (T⁴); it's not difficult at all to radiate heat from a hot object, as it is for a room-temperature one.
(How hot? I won't quote a number, but space nuclear reactors are generally engineered around molten metals).
hwillis · 2m ago
Yeah, fair to say its feasible. ROSA on the ISS produces 240 W/m^2 and weighs 4 kg/m^2.
The S6W reactor in the seawolf submarines run at ~300 C and produce 177 MW waste heat for 43 MWe. If the radiators are 12 kg/m^2 and reject 16x as much heat (call it 3600 W/m^2) then you can produce 875 watts of electricity per m^2 and 290 watts at the same weight as the solar panels. Water coolant at 300 C also needs to be pressurized to 2000+ PSI, which would require a much heavier radiator, and the weight of the reactor, shielding, turbines and coolant makes it very hard to believe it could ever be better than solar panels, but it isn't infeasible.
Plus, liquid metal reactors can run at ~600 C and reject 5x as much heat per unit area. They have their own problems: it would be extremely difficult to re-liquify a lead-bismuth mix if the reactor is ever shut off. I'm also not particularly convinced that radiators running at higher temperatures wouldn't be far heavier, but for a sufficiently large station it would be an obvious choice.
cma · 2h ago
But boiling water is just a few hundred Kelvin, this is tens of thousands. Would EVA spacesuits be able to radiate that much away if it was really that hot but for the atmosphere absorbing some?
I know it is much hotter, but that's way way hotter and they only find it at a "wall" way farther out.
This is more the temperature of the solar wind, dwarfing the steady state temperature you'd reach from the photonic solar radiation at any distance. The Sun's blackbody varies from like 5000K to 7000K, you won't see objects heated in the solar system heated higher than that even with full reflectors covering the field of view of the rear with more sun and being near the surface of the sun, other than a tiny amount higher from stellar wind, tidal friction, or nuclear radiation from the object's own material I don't think.
foxyv · 1h ago
> Would EVA spacesuits be able to radiate that much away if it was really that hot but for the atmosphere absorbing some?
Yes! The tiny number of particles are moving really fast, but there are very few of them. We are talking about vacuum that is less than 10^-17 torr. A thermos is about 10^-4 torr. The LHC only gets down to 10^-10 torr. At those pressures you can lower the temperature of a kilometer cube by 10 thousand kelvin by raising the temperature of a cubic centimeter of water by 1 kelvin. There is very little thermal mass in such a vacuum which is why temperature can swing to such wild levels.
This is also why spacecraft have to reject heat purely using radiation. Typically you heat up a panel with a lot of surface area using a heat pump and dump the energy into space as infrared. Some cooling paints on roofing do this at night which is kind of neat.
jamiek88 · 1h ago
To add to this: Most of the heat the EVA suits deal with is generated by the human inside not the giant ball of nuclear fusion 8 light minutes away.
rtkwe · 58m ago
Absorbed light too but that's a bit easier to deal with and is why most things are white or reflective on the outside of anything in space that's not intentionally trying to absorb heat.
semi-extrinsic · 1h ago
At this low density, temperature is very different from what you are used to experiencing. You have to work through a heat flux balance to really get a grasp of it.
Temperature is just the heat of particles moving. In the extreme case of a handful of N2 molecules moving at 1% the speed of light, it has a temperature of something like 9 billion Kelvin. But it's not going to heat you up if it hits you.
im3w1l · 1h ago
Okay this may sound silly but what about a solar powered ac for cooling? Like solar radiation is 6000K right, so if you used that to pump your waste heat into say a 1000K radiator (aimed away from the sun obviously) I'm thinking it might give you plenty of negentropy but also radiate away heat at a decent pace.
itishappy · 1h ago
Skip the Sun! There's an "atmospheric window" in the IR. If you make a material that emits/absorbs (they're reversible) only in that region, and don't expose it to the Sun, then it will cool down to the temperature of space, roughly 3K or -270°C. In practice, it won't cool down anywhere near that much. It'll steal energy from it's surroundings due to conduction/convection, and the amount of energy that's actually radiated in this band by a slightly below room temperature material is pretty minimal. Still neat, entirely passive cooling by radiating to space!
Acs don't get rid of heat, they just move it around. At some point you need to put the heat somewhere and then your just back to giant radiators
hwillis · 59m ago
Radiative heat transfer is proportional to T^4. If your suit is 300 K(80F), bumping the temperature up by 100 C lets you radiate 3.16x as much heat from the same area.
> An absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling process. Solar energy, burning a fossil fuel, waste heat from factories, and district heating systems are examples of heat sources that can be used. An absorption refrigerator uses two coolants: the first coolant performs evaporative cooling and then is absorbed into the second coolant; heat is needed to reset the two coolants to their initial states.
> Fishermen in the village of Maruata, which is located on the Mexican Pacific coast 18 degrees north of the equator, have no electricity. But for the past 16 years they have been able to store their fish on ice: Seven ice makers, powered by nothing but the scorching sun, churn out a half ton of ice every day.
Sharlin · 57m ago
Yes? That's in the atmosphere where heat rejection is a vastly easier problem than in vacuum, thanks to convection.
mrguyorama · 1h ago
It literally doesn't matter what your refrigeration process is. You have to "reject" the heat energy at some point. In space, you can only do that with large radiators.
There is no physical process that turns energy into cold. All "cooling" processes are just a way of extracting heat from a closed space and rejecting it to a different space. You cannot destroy heat, only move it. That's fundamental to the universe. You cannot destroy energy, only transform it.
Neither link is a rebuttal of that. An absorption refrigerator still has to reject the pumped heat somewhere else. Those people making ice with solar energy are still rejecting at minimum the ~334kj/kg to the environment.
An absorption refrigerator does not absorb heat, it's called that because you are taking advantage of some energy configurations that occur when one fluid absorbs another. The action of pumping heat is the same.
arscan · 1h ago
What is the temperature on either side of this “wall”? My mental model here, which is probably incorrect, is that the “temperature” on the outside of the wall could be higher but the density is much lower, thus even less heat transfer going on (but, still, high energy particles that can hit you, registering a high temperature). I get all kinds of mixed up regarding the difference between heat transfer and measured temperature.
pseudosavant · 53m ago
I thought the same thing too. It is very hot, without having very much heat - in a way.
The Parker Solar probe encounters a similar situation where it has to handle high amounts of direct radiation, but the latent/ambient environment is full of incredibly hot particles at very low density (because they are so hot) which means it isn't that hard to make the probe survive it.
DrBazza · 1h ago
Temperature is a totally valid measurement. For physicists. Not really for clickbait articles. High energy particles wouldn't attract as many views.
If it were really that hot we'd never observe the CMB at a balmy 2.7K.
LeratoAustini · 2h ago
I often think about how cold our lifeforms on earth are, relative to temperatures of things in the universe. 0 Kelvin is theoretical lowest possible temp, quasars are apparently > 10 trillion Kelvin (10,000,000,000,000K), yet all life we know of is between what, 250K and 400K?
Sniffnoy · 10m ago
Basically it's because the relevant structures are somewhat fragile. Matt Strassler has a good post about "why does everything we care about move so slowly compared to the cosmic speed limit?" (https://profmattstrassler.com/2024/10/03/why-is-the-speed-of...), and the answer is, it's because we're made of atoms, atoms are held together by the electromagenetic force, and that's only so strong, if things moved way faster then collisions would tear atoms apart. But of course life is dependent not only on atoms, but also on electromagnetic bonds much weaker than the ones that hold atoms together. So this limits how hot it can get.
robin_reala · 1h ago
0 Kelvin is theoretical lowest possible temp
Let me introduce you to negative temperature systems!
Negative temperatures are hotter than positive temperatures, though, so this isn't really relevant to the parent comment.
httpz · 4m ago
Well unless there's some ghost-like life form in a gas state, we sort of need the molecules to stay together to form life.
steve_adams_86 · 2h ago
I was aware of this, but you putting it into numerical terms rather than an intuitive understanding is really cool. Even a small fire is dramatically hotter than life, yet nothing in comparison to what happens outside of our relatively frozen little bubble here on Earth
Seems I no longer can edit it but that link doesn't directly reference the high temperature environment, unless I misread it?
cooper_ganglia · 2h ago
I remember being in school in 2006 and being told that outside of our solar system is a "wall of fire" that we would never be able to cross.
I don't know if any of this info was speculated at that point in time, but it turns out that teacher was at least partially correct!
jordanb · 2h ago
Probably true, in that if you try to travel interstellar distances you'll going to have to deal with very hot particles hitting your ship on occasion. If you travel slowly the more time you're going to be spend getting hit by high energy particles. If you try to travel quickly you're going to have to deal with more relatively high energy particles. It's potentially enough to make interstellar travel impossible.
strictnein · 1h ago
Systems we built in the 1970s were able to easily pass through this though. Which doesn't seem to indicate that it would make interstellar travel impossible.
andrewflnr · 1h ago
Systems from the 1970s travel at, by interstellar standards, agonizingly slow speeds. The voyagers will be exposed to hard radiation for thousands of years before they get anywhere interesting. They will not survive.
strictnein · 44m ago
Not sure exactly why you're responding to me. The comment I was responding to was talking about the hot particles that would be encountered, and that their existence could preclude future interstellar missions.
What level of "hard radiation" are they now getting bombarded by that we will be unable to shield systems from in far future interstellar space travel?
SoftTalker · 1h ago
It's impossible for many reasons unless there are physics we haven't discovered yet. To me that's the simple answer for the Fermi paradox.
andrewflnr · 1h ago
The Fermi paradox doesn't require travel, though. The lack of any sign of life at all is still surprising (no radio signals, etc), even if we knew it couldn't physically come here.
relaxing · 1h ago
That’s weird. What class was it and what was their motivation for telling you this?
anigbrowl · 41m ago
It's great that we're still getting data from these two probes 50 years later but it absolutely sucks that these are the only 2 probes we have out there. How long can they keep running, another 5 or 10 years max? It's already considered an engineering miracle that they are still going.
What of people growing up 10, 20, 30 years from now? They'll be taught in school about stuff from Voyager and then told 'and that was what we learned in the golden age of space exploration, which ended long before you were born because we couldn't be bothered to keep at it.' Having grown up in the 70s, I feel somewhat betrayed that we just just gave up on doing moon stuff, rendering a whole generation's aspirations on space exploration into a lie. The claims that 'there is nothing more to discover up/out there' is nonsense, much like the claims that 'chips can't be made any smaller' that I would hear back in the 32nm period.
The lack of long-term commitment to exploratory space is a terrible waste. To be sure we have been doing some stuff in system, but if he had kept putting out deep space probes every few years with more advanced instruments we would have learned a lot of other things by now, and we would have a long-term stream of new data coming in for the future. Now arguments for launching more deep space probes are dismissed with 'it'll take decades before we get anything useful back.' Yeah, because we stopped iterating! Meantime allowing that sort of exploration to become anachronistic is one reason we are overrun with flat-earthers and other science woo even at the highest levels of government.
jakeydus · 2h ago
Thought this was an interesting example of reading the headline vs reading the article.
Headline:
> NASA's Voyager found a 30k-50k Kelvin "Wall"...
Article:
> While not a hard edge, or a "wall" as it has sometimes been called...
kibwen · 2h ago
What sensor is Voyager using to measure "temperature" here?
It seems they use several tools - inferring from the descriptions, they can measure and compare the data when it gets back here to determine simple things like temps.
1970-01-01 · 30m ago
What happens when an object enters a solar orbit inside this wall? Theoretically, it could be heated to life-sustaining temperatures?
stuff4ben · 2h ago
Fascinating that we're still getting useful science out of almost 50 year old tech. I think New Horizons is the only other probe that's expected to go interstellar.
flippyhead · 1h ago
This is obviously the thing aliens have setup to obscure themselves from us. Obviously.
ElijahLynn · 2h ago
"While not a hard edge, or a "wall" as it has sometimes been called, here both spacecraft measured temperatures of 30,000-50,000 kelvin (54,000-90,000 degrees Fahrenheit), which is why it is sometimes also referred to as a "wall of fire". The craft survived the wall as, though the particles they measured were extremely energetic, the chances of collision in this particle-sparse region of space are so low that not enough heat could be transferred to the duo."
archermarks · 2h ago
Also, worth noting that these temperatures are not that high as far as plasmas go. This is 3-5 eV, which is firmly in the "low temperature" regime (like a fluorescent bulb).
dogma1138 · 2h ago
Is there a chance this is an instrument error? Seems a strange phenomenon.
gmueckl · 2h ago
This isn't strange at all, but rather an artifact of the nature of heat energy in a medium. Heat is the uncorrelated movement of particles that evens out to zero effective velocity. Temperature is the measure of the velocity magnitude of these individual particles. This is independent of the medium's density.
koolala · 1h ago
That's the best part of them sending two of them. It can't be a random error.
echelon · 2h ago
I'm just a layperson, but I'd suspect the research is sound.
I hate the telephone tag, livescience.com-type journalism. Instead, I'd love to read an abstract and methods. The research must talk about this in detail and explain how the conclusions are reached. It probably isn't too inaccessible.
I suspect that there may be many such measurements correlated between both probes taken against some other baseline signal or an observed return to the mean.
TheBigSalad · 1h ago
Can someone explain to me why this isn't melting Voyager?
threeducks · 1h ago
> why this isn't melting Voyager?
Same reason why you can sit in a sauna with very hot air or pass your hand through a flame quickly without severe burns. Low density matter does not transfer heat very well. And space is especially devoid of matter.
jandrese · 47m ago
There is no thermal mass. It's almost pure vacuum but the handful of particles that are out there are whizzing around at high energies that make them very hot.
Interesting to think that while it's not a concern to Voyager at its pokey 17km/second, a true interstellar ship traveling at some respectable fraction of C would compress the diffuse interstellar gasses enough to make them a potential hazard. You frequently see people saying stuff like "if we could accelerate to a high fraction of C you could get anywhere in the galaxy in a single lifetime", but it may not be so simple.
Terr_ · 1h ago
The average stuff is very hot, but there's also basically no stuff out there anyway, so you won't run into enough of it to care.
Imagine that there is one venomous and aggressive snake (in a cute little survival-suit) in some random spot in Antarctica. This means "the average snake in Antarctica" is ultra-dangerous.
But there's only one, and it's almost impossible for you ever to meet, so in practical terms it's still safer than Australia. :p
spiritplumber · 1h ago
High temperature, almost no actual heat because there are very few particles.
mvdtnz · 33m ago
This is explained in the article.
robin_reala · 1h ago
The craft survived the wall as, though the particles they measured were extremely energetic, the chances of collision in this particle-sparse region of space are so low that not enough heat could be transferred to the duo.
Temperature is a measure of the kinetic energy of a particle, so they can be both extremely hot and extremely diffuse.
mystified5016 · 1h ago
Because very few hot particles ever touched the craft. The gas is so incredibly thin that Voyager largely sailed straight through the space in between molecules.
righthand · 2h ago
Very cool, our solar system has an atmosphere, which seems obvious but isn’t discussed or taught at least when I was in high school.
knappe · 1h ago
One of my favorite quotes from one of my Astro professors is "Everything has an atmosphere, it is a matter of how tenuous".
I think the article shows how relevant this still is today.
IAmBroom · 2h ago
Basically, the Oort cloud. Except for the high temps, which are the surprise.
righthand · 1h ago
From my understanding the wall is not the Oort cloud but instead the solar winds bouncing off the exterior winds more like how the Pacific and Atlantic oceans don’t mix.
hotpocket777 · 1h ago
Well, not a surprise. They predicted it before measuring it.
acc_297 · 2h ago
In both Edge and Firefox I'm blocked for using Adblock but from what I can tell I do not have adblock on either browser.
danjc · 2h ago
Which side of the wall were you on?
redundantly · 1h ago
This made me giggle
jlarocco · 2h ago
That's funny... I'm using Firefox, definitely have an ad-blocker, and had no problem.
righthand · 2h ago
Firefox has enhanced tracking protection and I got through fine with it set to “strict”. Are you on a vpn?
acc_297 · 1h ago
Ah yes, I turned off a bunch of Kaspersky internet security settings and I'm through. This is my work computer I forget what's running in the background sometimes.
Made me think of this Brin book. The first ship to try to leave the solar system, crashes into an invisible crystal barrier. It's unbreakable.
IAmBroom · 2h ago
While in the very-much-breakable sphere around Earth category, there's Unsong (https://unsongbook.com) by Scott Alexander.
CamperBob2 · 2h ago
I'm confused. The plot summary talks about an impenetrable sphere around our solar system, but also says, "The main character takes part in an expedition to a newly discovered habitable solar system with a shattered sphere." How'd the character escape from our own system?
cosmicgadget · 2h ago
Says it right here:
> From studying the Nataral's artifacts and writings, they learn that the only way to break the crystal spheres is from the inside.
He just had to go to the other solar system to learn how to go to the other solar system.
throwawayffffas · 1h ago
> It is also discovered that the Nataral chose to go into a kind of suspended animation around a black hole, joining two even earlier species, to wait for the other civilizations of the universe to develop interstellar flight capabilities.
They used their interstellar flight capabilities to go wait for someone in the universe to develop interstellar flight capabilities. Checks out.
clort · 54m ago
If I recall (its been 25+ years and my copy is in storage), they went there to wait for other civilisations to develop. They were truly early life and there was literally nobody else and they determined that they would be waiting for millions of years, if not billions.
I don't know if it was this book, but the 'suspended animation' was basically pushing several large stars and neutron stars close enough together that the flat space between them was inside an encompassing event horizon, and there they waited, living their lives at an extremely slow (compared to the outside universe) pace.
pulvinar · 2h ago
It crashes into the sphere, but must have also broken it: "the only way to break the crystal spheres is from the inside".
throwawayffffas · 1h ago
Yeah found it online, the ship that crashed on it broke it.
You only get fire risks when the things they touch are themselves tiny (like dust), so they're unable to absorb and spread the heat.
A similar thing happens when you bake with tinfoil. The foil will be at like 350 F, but you can still touch it basically immediately if you're willing to gamble that nothing with thermal mass is stuck to it where you can't see. It just doesn't have enough thermal mass on its own to burn you, but if there's a good-sized glob of cheese or water or something on the other side you can really be in for a nasty surprise.
https://en.wikipedia.org/wiki/Tin_foil
Then there's the fact that heat is very difficult to get rid of when in space. The ISS's radiators are much bigger than its solar panels. If you wanted to have a very-long eva spacesuit you'd have to have radiators much bigger than your body hanging off of it. Short evas are handled by starting the eva with cold liquids in the suit and letting them heat up.
All of the mockups of starships going to Mars mostly fail to represent where they're going to put the radiators to get rid of all the excess heat.
I was curious about this! The Extravehicular Mobility Units on the ISS have 8 hours of life support running on 1.42 kg of LiOH. That releases ~2 kJ per gram used, so .092 watts.
The 390 Wh battery puts out an average of 50 watts.
And the human is putting out at minimum 100 watts with bursts of 200+.
Long term it's probably reasonable to need at least 200 watts of heat rejection. That's about a square meter of most radiator, but it needs to be facing away from the station. You could put zones on the front/back and swap them depending on direction, as long as you aren't inside an enclosed but evacuated area, like between the Hubble and the Shuttle. The human body has a surface area of roughly 2 m^2 so its definitely not enough to handle it- half of that area is on your arms or between your legs and will just be radiating onto itself.
It's also not very feasible to have a sail-sized radiator floating around you. You'd definitely need a more effective radiator- something that absorbs all your heat and glows red hot to dump all that energy.
That also makes nuclear totally infeasible- since turbines are inefficient you'd need 2.5x as many radiators to reject waste heat. Solar would be much lighter.
https://en.wikipedia.org/wiki/Spacecraft_thermal_control#Rad...
(How hot? I won't quote a number, but space nuclear reactors are generally engineered around molten metals).
The S6W reactor in the seawolf submarines run at ~300 C and produce 177 MW waste heat for 43 MWe. If the radiators are 12 kg/m^2 and reject 16x as much heat (call it 3600 W/m^2) then you can produce 875 watts of electricity per m^2 and 290 watts at the same weight as the solar panels. Water coolant at 300 C also needs to be pressurized to 2000+ PSI, which would require a much heavier radiator, and the weight of the reactor, shielding, turbines and coolant makes it very hard to believe it could ever be better than solar panels, but it isn't infeasible.
Plus, liquid metal reactors can run at ~600 C and reject 5x as much heat per unit area. They have their own problems: it would be extremely difficult to re-liquify a lead-bismuth mix if the reactor is ever shut off. I'm also not particularly convinced that radiators running at higher temperatures wouldn't be far heavier, but for a sufficiently large station it would be an obvious choice.
I know it is much hotter, but that's way way hotter and they only find it at a "wall" way farther out.
This is more the temperature of the solar wind, dwarfing the steady state temperature you'd reach from the photonic solar radiation at any distance. The Sun's blackbody varies from like 5000K to 7000K, you won't see objects heated in the solar system heated higher than that even with full reflectors covering the field of view of the rear with more sun and being near the surface of the sun, other than a tiny amount higher from stellar wind, tidal friction, or nuclear radiation from the object's own material I don't think.
Yes! The tiny number of particles are moving really fast, but there are very few of them. We are talking about vacuum that is less than 10^-17 torr. A thermos is about 10^-4 torr. The LHC only gets down to 10^-10 torr. At those pressures you can lower the temperature of a kilometer cube by 10 thousand kelvin by raising the temperature of a cubic centimeter of water by 1 kelvin. There is very little thermal mass in such a vacuum which is why temperature can swing to such wild levels.
This is also why spacecraft have to reject heat purely using radiation. Typically you heat up a panel with a lot of surface area using a heat pump and dump the energy into space as infrared. Some cooling paints on roofing do this at night which is kind of neat.
Temperature is just the heat of particles moving. In the extreme case of a handful of N2 molecules moving at 1% the speed of light, it has a temperature of something like 9 billion Kelvin. But it's not going to heat you up if it hits you.
https://en.wikipedia.org/wiki/Atmospheric_window
https://en.wikipedia.org/wiki/Passive_daytime_radiative_cool...
for PDRC there are a couple good videos about it from NightHawkInLight https://youtu.be/N3bJnKmeNJY?t=19s, https://youtu.be/KDRnEm-B3AI and Tech Ingredients https://www.youtube.com/watch?v=5zW9_ztTiw8 https://www.youtube.com/watch?v=dNs_kNilSjk
> An absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling process. Solar energy, burning a fossil fuel, waste heat from factories, and district heating systems are examples of heat sources that can be used. An absorption refrigerator uses two coolants: the first coolant performs evaporative cooling and then is absorbed into the second coolant; heat is needed to reset the two coolants to their initial states.
https://www.scientificamerican.com/article/solar-refrigerati...
> Fishermen in the village of Maruata, which is located on the Mexican Pacific coast 18 degrees north of the equator, have no electricity. But for the past 16 years they have been able to store their fish on ice: Seven ice makers, powered by nothing but the scorching sun, churn out a half ton of ice every day.
There is no physical process that turns energy into cold. All "cooling" processes are just a way of extracting heat from a closed space and rejecting it to a different space. You cannot destroy heat, only move it. That's fundamental to the universe. You cannot destroy energy, only transform it.
Neither link is a rebuttal of that. An absorption refrigerator still has to reject the pumped heat somewhere else. Those people making ice with solar energy are still rejecting at minimum the ~334kj/kg to the environment.
An absorption refrigerator does not absorb heat, it's called that because you are taking advantage of some energy configurations that occur when one fluid absorbs another. The action of pumping heat is the same.
The Parker Solar probe encounters a similar situation where it has to handle high amounts of direct radiation, but the latent/ambient environment is full of incredibly hot particles at very low density (because they are so hot) which means it isn't that hard to make the probe survive it.
If it were really that hot we'd never observe the CMB at a balmy 2.7K.
Let me introduce you to negative temperature systems!
https://en.wikipedia.org/wiki/Negative_temperature
I don't know if any of this info was speculated at that point in time, but it turns out that teacher was at least partially correct!
What level of "hard radiation" are they now getting bombarded by that we will be unable to shield systems from in far future interstellar space travel?
What of people growing up 10, 20, 30 years from now? They'll be taught in school about stuff from Voyager and then told 'and that was what we learned in the golden age of space exploration, which ended long before you were born because we couldn't be bothered to keep at it.' Having grown up in the 70s, I feel somewhat betrayed that we just just gave up on doing moon stuff, rendering a whole generation's aspirations on space exploration into a lie. The claims that 'there is nothing more to discover up/out there' is nonsense, much like the claims that 'chips can't be made any smaller' that I would hear back in the 32nm period.
The lack of long-term commitment to exploratory space is a terrible waste. To be sure we have been doing some stuff in system, but if he had kept putting out deep space probes every few years with more advanced instruments we would have learned a lot of other things by now, and we would have a long-term stream of new data coming in for the future. Now arguments for launching more deep space probes are dismissed with 'it'll take decades before we get anything useful back.' Yeah, because we stopped iterating! Meantime allowing that sort of exploration to become anachronistic is one reason we are overrun with flat-earthers and other science woo even at the highest levels of government.
Headline: > NASA's Voyager found a 30k-50k Kelvin "Wall"... Article: > While not a hard edge, or a "wall" as it has sometimes been called...
It seems they use several tools - inferring from the descriptions, they can measure and compare the data when it gets back here to determine simple things like temps.
I hate the telephone tag, livescience.com-type journalism. Instead, I'd love to read an abstract and methods. The research must talk about this in detail and explain how the conclusions are reached. It probably isn't too inaccessible.
I suspect that there may be many such measurements correlated between both probes taken against some other baseline signal or an observed return to the mean.
Same reason why you can sit in a sauna with very hot air or pass your hand through a flame quickly without severe burns. Low density matter does not transfer heat very well. And space is especially devoid of matter.
Interesting to think that while it's not a concern to Voyager at its pokey 17km/second, a true interstellar ship traveling at some respectable fraction of C would compress the diffuse interstellar gasses enough to make them a potential hazard. You frequently see people saying stuff like "if we could accelerate to a high fraction of C you could get anywhere in the galaxy in a single lifetime", but it may not be so simple.
Imagine that there is one venomous and aggressive snake (in a cute little survival-suit) in some random spot in Antarctica. This means "the average snake in Antarctica" is ultra-dangerous.
But there's only one, and it's almost impossible for you ever to meet, so in practical terms it's still safer than Australia. :p
Temperature is a measure of the kinetic energy of a particle, so they can be both extremely hot and extremely diffuse.
I think the article shows how relevant this still is today.
Made me think of this Brin book. The first ship to try to leave the solar system, crashes into an invisible crystal barrier. It's unbreakable.
> From studying the Nataral's artifacts and writings, they learn that the only way to break the crystal spheres is from the inside.
He just had to go to the other solar system to learn how to go to the other solar system.
They used their interstellar flight capabilities to go wait for someone in the universe to develop interstellar flight capabilities. Checks out.
I don't know if it was this book, but the 'suspended animation' was basically pushing several large stars and neutron stars close enough together that the flat space between them was inside an encompassing event horizon, and there they waited, living their lives at an extremely slow (compared to the outside universe) pace.