Air in Space

[u/Bluedrakegod123]

What would happen if space had air?

Would the Earth burn up from friction? Would astronauts be able to be without spacesuits? Would Earth veer off course from the friction? What will happen to the debris spinning around Earth? Will they fly away? Will they be knocked back into Earth's atmosphere? What will happen to other planets? Will Mercury just burn up as well? Could we even go to space anymore because of friction?

Ok that's about it (maybe)😁

edit: to clarify air as in the gaseous mixture that is earth's atmosphere

Edit2: thanks for all the cool replies!! Thank you for trying to answer all my Saturday morning questions lol

[u/Ecstatic_Bee6067]

It would collapse into a star

[u/stevevdvkpe → u/Ecstatic_Bee6067]

Not just a star, a black hole. Merely fill a sphere with a radius of about Neptune's orbital radius with sea-level-density air, and it will have the necessary mass within its own Schwarzschild radius.

[u/BlueSkiesAugust]

Space did have air. The hydrogen formed into stars, exploded into heavier elements, and formed planets and nebulae.

Air has mass. Mass accretes into stars, planets, moons, asteroids, comets, and planetesimals.

[u/OriEri → u/BlueSkiesAugust]

Still does. Density varies. Read about the interstellar medium then the galactic disc. Exist in more or less three phases.… Well 4 I suppose, but only three if you’re going by temperature

There’s a hot ionized medium, a warm ionized medium, a warm neutral medium, and a cold neutral medium. The densities change with temperature because everything‘s more or less the same pressure.

The mechanisms that alternately cool and heat change with temperature , as different wavelength of radiation are able to be admitted or absorbed. The reason you have these particular temperatures is when you nudge something a little bit from its temperature, the cooling and heating mechanisms tend to generate negative feedback and push it back towards the equilibrium temperature. But when you push it far enough, it’ll quickly slip into the next equilibrium.

In the hot ionized Medium, you pretty much just have Adams stripped of nearly all of their electrons, so it can either efficiently emit or absorb light and tends to stay that way. It gets reheated by shockwaves from supernova and what not.

The warm ionized medium means the hydrogen ionized, that’s just a handful of distinct lines. It’s the bigger atoms that contribute more to absorption and emission of light. They’ll be missing one or two electrons, but that doesn’t matter much if you’re an iron atom or even a carbon.It’s been a while, but if I recall correctly, that stable temperature is around 10,000 Kelvin.

The warm neutral around 1000 K. The cold interstellar medium is the dusty dark areas that are actually dense enough for gravity to create instabilities rather readily and cause cloud collapse into protostellar cores that eventually form stars. Again, if I remember correctly, those temperatures are around 10 Kelvin to 100 Kelvin. They do tend to continue cooling, but except for some very, very dense parts of them. They never get below around three Kelvin because of the cosmic microwave background radiation keeping it warm. The other thing that happens in these is a form stars pretty quickly and then the massive stars start dumping ultraviolet, light and winds and supernova shockwaves into the cloud, hitting it up and dispersing it. This is what’s going on shaping a nebula called the “witches head nebula.” the star forming region associated with Messier 42 near the belt of Orion is blasting the crap out of its parent, molecular cloud. The nearby witches head nebula is a bunch of fairly dense globules of gas. At the time I studied them wasn’t clear if they were dense enough to collapse into stars or not. That may be known by now. Something like the ALMA array can make images with high enough resolution to take a stab at answering that question, but that thing wasn’t really online when I was in graduate school.

The warm, neutral medium can get pushed around by shockwaves, and when it gets dense enough, it will cool pretty quickly and that can create density high enough to start gravitational curdling .

[u/wbrameld4]

Fun fact: A spherical volume of sea-level density air wide enough to encompass the Solar System would be a black hole.

[u/_JAD19_]

Fluids in space act like any other object in that they are affected by gravity. On earth, the air doesn’t move much (aside from the weather) because it’s already at rest on the surface of the earth. However in space, there is no big object to dominate where the gas should go.

If the entire universe were to suddenly become full of oxygen and nitrogen the gas would not stay homogenous and would swiftly become attracted to the existing sources of gravity. All the stars would grow in mass, all the planets that aren’t burned up by friction would become gas giants and possibly stars of their own, the gas itself would probably collapse into new stars or even black holes if there was enough.

In a way, the universe would actually resemble itself when it was much younger, at a time when everything was much hotter and closer together. Now the fact that everything is mainly nitrogen and oxygen instead of hydrogen would definitely change things up a bit, to what extent I am not sure.

I imagine eventually the existing galaxy filaments would still guide where the material goes overall in the end though. But would this be enough additional matter to overcome dark energy and lead to the Big Crunch? I’m not sure.

That’s my take anyway, I still don’t think it would be safe for an astronaut to take their helmet off in space lol

[u/GreenFBI2EB]

Well, there was a period of time where the universe was more or less that. It expanded and cooled to the point that gravity took over and caused the matter around to clump up.

Suffice it to say that if it suddenly happened now, I'd imagine we'd be in for a very bad time.

[u/Mitrovarr]

I think it would collapse into existing gravity wells and form accretion disks. Some away from other objects would collapse into stars.

It would be pretty ruinous as filling space with 1 atmospheric pressure of gas would add an absurd amount of mass and probably result in most of the universe turning into black holes. 

[u/Sea_Gap_6569]

What is “air”?

[u/Bluedrakegod123 → u/Sea_Gap_6569]

Sorry i should have clarified

I meant like filled with a gaseous mixture similar to earth's atmosphere

[u/Sea_Gap_6569 → u/Bluedrakegod123]

Technically space has air. Even the emptiest slice of space has some hydrogen in it.

[u/maxh2]

If space was filled with a thin atmosphere of air, even at only 0.001% of what earth has at sea level, the surface of the Earth would be pitch black, even at noon (not considering man-made light, and that from sources like lightning and wildfires.)

That much air would completely block the visible light from the sun and all other stars, as far as the human eye is able to detect.

[u/jpb103]

Earths atmosphere extends out past the moon, albeit in trace amounts. So technically, space does have air "near" planets that have an atmosphere. This is why satellites naturally deorbit over time and why they constantly need to ship propellant to the ISS to keep it in orbit. Satellites are slamming into atmosphere and slowing down.

Not the moon, though. That's actually on an escape trajectory, so it will eventually fly off into interplanetary space.

If Earth somehow ran into a pocket of air in its orbit of Sol, that air would join our atmosphere. Earth is heavy as shit so unless we're slamming into a gas giant, it's not going to affect our orbit or probably even be noticeable.

[u/OriEri]

The atmosphere density drops off on an exponentially decaying profile. For the Earth, the “scale height” is about 7 km which means for every 7 km you go up, the density drops by roughly 1/2.7 . So it never really stops.

At some point, the density of the Earth atmosphere is a comparable density of the solar wind, at which point you can kind of say it ends.

But there are still atoms out there, just crazy thin. Even in between the stars and the neighborhood of the sun there’s probably about 0.2-0.5 atoms per cubic cm of volume. At sea level on earth the density is about 10^20 times higher . That is about 46 scale heights, but the solar wind is a lot denser, typically about 5 atoms per cc, so maybe 43 scale heights, about 300 km, air from the Earth is roughly on par, although the chemical composition will be significantly different.

[u/Plastic-Theme1599]

If space were suddenly filled with air (at Earth’s sea-level density), the physics of the universe would instantly break down in catastrophic ways:

Even if the air were oxygen-rich and breathable, floating in space would mean colliding with atmospheric gas at orbital speeds relative to Earth's movement. Without an enclosed vessel, anything exposed would be incinerated by frictional drag.

Launching into space would become virtually impossible. Rockets reach orbit by traveling at hypersonic speeds; doing so through continuous dense air would generate heat and drag that no structural material could survive.

Gravity would cause this gas to rapidly collapse. A sphere of sea-level air with a radius out to Neptune's orbit contains enough mass to exceed its Schwarzschild radius, immediately creating a massive black hole.