Well, given a sphere of air stretching out to Neptune would only be around 6.5x its Schwarzschild radius in diameter, I imagine it would very quickly collapse into a black hole. There definitely won't be enough time to fly airships around or hear the sound from the Sun before the planets are shredded by the air (which is moving at roughly Mach 80 in the case of Earth), even if they didn't fall into the new black hole.
this post was submitted on 08 Sep 2024
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This would be a good xkcd what-if, right up Randall's alley.
If you're talking about Earth-like atmospheric density, I can tell you that that is a lot of mass.
So first off, if it's not rotating, it's gonna collapse into the Sun. And I'd guess, without looking at the numbers, that it's probably gonna be some combination of processes that are gonna ultimately result in a black hole where the Sun is now.
If it's rotating, then there's a problem. You can't just have air staying in orbit in arbitrary orbits, because it'll collide. So I guess that you'd have to have a flat ring of gas, like Saturn's rings. Basically, it'd have an orbit of zero eccentricity.
The planets don't have an orbit of zero eccentricity, so they'd be smacking into air constantly. Aside from the effects of all of that air being captured by the planets themselves and adding to their mass, I'd guess that it'd tend to force them towards a zero eccentricity orbit.
If you have that gas ring, there may be more-dramatic near-term effects, but I would guess, again without looking at the numbers, that the planets would accrue it over time, and it'd have drastic effects on the planets; a lot of mass showing up, to say nothing of the chemical effects of oxygen and the thermal effects of colliding with the air.
It'd also add a lot of mass with rotational energy at orbital speed, so I assume that it'd make it easier for the Sun to capture stuff passing through that gas disc.
I don't know what effects would be sooner or dominate, but I think that it'd probably be pretty exciting in more unpleasant ways than the flying airplanes between planets thing that you mentioned.
EDIT: Hah, did this before reading mindbleach's comment, and he hit some of the same points.
Science values independent discovery of exactly how fucked we are.
I hadn't considered foreign asteroids. If this ridiculous setup was somehow stable, bits of it would routinely light up from space rocks plunging through at terrifying speed. Hailey's comet is coming back to stay.
Lots of fire
Now I'm curious if everything orbiting in space would "burn up" from the sudden friction like when an orbiting object comes into contact with an atmosphere.
This sounds like an XKCD what-if that ends with an explosion that could deafen god himself.
Like, if it just pops into existence, "static" relative to the sun, it'd all slowly fall into the sun. The solar system is ehhh 100 AU wide, atmospheric density's about 1 kg per cubic meter, 1 AU is ~1.5e11 m... volume of a sphere is 4/3 * pi * r^3... that'd be 4.5e39 kg of gases, or basically 500,000,000 times the current mass of the sun. So, at a wild guess, probably enough to form a black hole? But it cannot be good for the inner solar system either way. Especially not if we work out how an Earth-shaped column of that gas falls into the sun with Earth in the way.
(Edit: Sagittarius A* is only 4e6 solar masses. 5e8 is borderline supermassive. Things would go poorly.)
If it spins instead - if it's all playing nicely with the orbits of each planet and the general flow of the asteroid belt - we probably don't all die fantastically. At least not for a while. We can assume it'd be a plane instead of a sphere, maybe 1 AU thick, as if the sun had rings. I don't think it'd just diffuse out into the cosmos? Once all that mass is orbiting, you'd only lose the weird exceptional atoms that reach the edge with a bunch of energy and then don't hit anything for a zillion miles. That also happens at the top of Earth's atmosphere, and we've got gravity keeping it in check. So let's just hand-wave that this situation lasts, like, at all.
Those bands in the rings will experience friction. Any speed differential has consequences, and I do not want to think about the computation requirements for that kind of fluid simulation. I think at worst they'd separate. They can't all take the same angular velocity because that's not how orbits work. They might fuck up the planets moving through them? Like, I don't know much about astrophysics, but when a planet has rings it's not because things went well for the satellites in that range.
Actually that highlights how the planets would have the same issue as the sun, if a bunch of mass magically appeared overhead, in their reference frame: it'd fall. Air doesn't weigh much, but when you hand-wave an entire gazillion miles of it, that adds up. We'd have problems well before the atmosphere started to outpace the entire solid mass of Earth.
If this atmosphere orbits each planet, the way the whole shebang orbits the sun - you're back to speed differentials. Just thinking locally: there'd be different spin for air that refuses to fall toward Earth, and air that refuses to fall toward the moon, and somewhere in the middle those two streams would meet. Or - at best! - they wouldn't quite meet. The gaps would separate themselves. You could maybe do a cool sci-fi setting with that, but your space 747 would need to zoop clean out of Earth's sky-ocean and catch the moon's.
Oh. And I don't think sunlight would be visible through one hundred and fifty million kilometers of atmosphere. At least, until the sun slurped up a couple yottatons of it, at which point we'd have whole new problems.
You say that air doesn't weigh much but 1 atmosphere of pressure is already 14.7 pounds pee square inch at sea level. That's enough to flatten a steel barrel if a vacuum is pulled inside it. The consequences of increased atmospheric pressure at the earths surface alone would be nothing short of a mass extinction event. Every planet would become a gas giant, and potentially even brown dwarfs if not stars in their own rights. I bet Saturn and Jupiter would ignite at the very least.
If we thought global warming was bad, the heating of the gas accretion combined with the insulating effects of a thicc atmosphere would likely completely eradicate all life.
On the plus side, it would be one hell of a show before all life burns out of existence.
Yeah, this question kinda undersells how it's sprinkling a couple aspirational rocks into an enormous cosmic gas cloud, rather than providing those rocks with a quaint environment. Even the provolone-slice model that's 1 AU thick is only lighter by two orders of magnitude. It's one million times the total mass of everything else in the solar system. Spreading it on as thickly as our soupy atmosphere, where even certain mammals can flap hard enough to hunt in midair, would have an impact on world events the way a period impacts a sentence.
thatβd be 4.5e39 kg of gases, or basically 500,000,000 times the current mass of the sun. So, at a wild guess, probably enough to form a black hole?
Yeah, the Sun is IIRC something like within an order of magnitude what would be required.
kagis
https://public.nrao.edu/ask/what-is-the-critical-mass-at-which-a-star-becomes-a-black-hole/
In general, stars with final masses in the range 2 to 3 solar masses are believed to ultimately collapse to a black hole.
EDIT:
https://en.wikipedia.org/wiki/List_of_most_massive_black_holes
Yeah, based on your estimate and that list, it looks like it'd make the solar system into something like the 90th-largest supermassive black hole that humanity knows about.
The center of our galaxy, the Milky Way, has a black hole that'd be dwarfed by what our solar system would turn into.
https://en.wikipedia.org/wiki/Milky_Way
he Milky Way[c] is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye.
It is estimated to contain 100β400 billion stars[30][31] and at least that number of planets.[32][33] The Solar System is located at a radius of about 27,000 light-years (8.3 kpc) from the Galactic Center,[34] on the inner edge of the Orion Arm, one of the spiral-shaped concentrations of gas and dust. The stars in the innermost 10,000 light-years form a bulge and one or more bars that radiate from the bulge. The Galactic Center is an intense radio source known as Sagittarius A*, a supermassive black hole of 4.100 (Β± 0.034) million solar masses.[35][36] The oldest stars in the Milky Way are nearly as old as the Universe itself and thus probably formed shortly after the Dark Ages of the Big Bang.[37]
https://en.wikipedia.org/wiki/Sagittarius_A*
Sagittarius A*, abbreviated as Sgr A* (/ΛsΓ¦dΚ ΛeΙͺ stΙΛr/ SADGE-AY-star[3]), is the supermassive black hole[4][5][6] at the Galactic Center of the Milky Way. Viewed from Earth, it is located near the border of the constellations Sagittarius and Scorpius, about 5.6Β° south of the ecliptic,[7] visually close to the Butterfly Cluster (M6) and Lambda Scorpii.
The object is a bright and very compact astronomical radio source. The name Sagittarius A* distinguishes the compact source from the larger (and much brighter) Sagittarius A (Sgr A) region in which it is embedded. Sgr A* was discovered in 1974 by Bruce Balick [de] and Robert L. Brown,[8][9] and the asterisk * was assigned in 1982 by Brown,[10] who understood that the strongest radio emission from the center of the galaxy appeared to be due to a compact non-thermal radio object.
The observations of several stars orbiting Sagittarius A*, particularly star S2, have been used to determine the mass and upper limits on the radius of the object. Based on mass and increasingly precise radius limits, astronomers have concluded that Sagittarius A* must be the central supermassive black hole of the Milky Way galaxy.[11] The current best estimate of its mass is 4.297Β±0.012 million solar masses.[2]
So the Sol system would instantly become about 100 times more massive than Sagittarius A*.
I don't know if all of that mass would actually wind up in the resulting black hole -- I assume that the collapse of all that nitrogen and oxygen and such coreward would induce nuclear fusion and a supernova would blow some of the mass of what had been the Sol system outwards.
Yeah, sounds like most of the mass may get blown away before some of the remaining can collapse into a supermassive black hole.
Apparently this would have about five times the mass of "Scary Barbie".
https://en.wikipedia.org/wiki/AT_2021lwx
AT 2021lwx (also known as ZTF20abrbeie or "Scary Barbie"[2]) is the most energetic non-quasar optical transient astronomical event ever observed, with a peak luminosity of 7 Γ 10^45 erg per second (erg sβ1) and a total radiated energy between 9.7 Γ 10^52 erg to 1.5 Γ 10^53 erg over three years.[2][1] Despite being lauded as the largest explosion ever, GRB 221009A was both more energetic and brighter. It was first identified in imagery obtained on 13 April 2021 by the Zwicky Transient Facility (ZTF) astronomical survey[3] and is believed to be due to the accretion of matter into a super massive black hole (SMBH) heavier than one hundred million solar masses (Mβ).
Subrayan et al. originally interpreted it to be a tidal disruption event between an SMBH (~10^8 Mβ) and a massive star (~14 Mβ).[2] Wiseman et al. disfavor this interpretation, and instead believe the most likely scenario is "the sudden accretion of a large amount of gas, potentially a giant molecular cloud"[1] (~1,000 Mβ),[6] onto an SMBH (>10^8 Mβ).[1][7]
The inferred mass of the SMBH, based on the light to mass ratio, is about 1 hundred million - 1 billion solar masses, given the observed brightness. However, the theoretical limit for an accreting super massive black hole is 1 hundred million solar masses. Given the best understood model of accreting SMBH's, this even may be the most massive SMBH to possibly accrete matter.
That's maybe a hundred million solar masses, and mindbleach is figuring that we're dealing with about five hundred million solar masses.
So assuming that the gas composition isn't a factor here, I'd guess that we'd probably wind up turning ourselves into the largest explosion that humanity has ever observed in the universe, as the nitrogen undergoes gravity-induced nuclear fusion.
EDIT: Actually. Hmm. There's some portion of hydrogen gas in the atmosphere. According to this, it's mostly in water vapor. It's not much:
https://byjus.com/question-answer/what-percentage-of-the-earths-atmosphere-is-hydrogen/
The top 3 gases of the dry atmosphere are Nitrogen, Oxygen and Argon. Together they make up 99.96% of the atmosphere. All the remaining gases make up the remaining 0.04% of the atmosphere and Hydrogen is not even in the top 10. According to Wikipedia hydrogen makes up 0.000055% of the atmosphere but I wouldn't assume that it is all that accurate as it is such a small amount.
But I guess that it might be sufficient to start undergoing fusion prior to the nitrogen and blast most of the stuff apart prior to the nitrogen undergoing fusion.
Ditto for the carbon in the carbon dioxide, even if the hydrogen isn't enough.
Iβd guess that weβd probably wind up turning ourselves into the largest explosion that humanity has ever observed in the universe.
With front-row seats.
Does this mean if we had a huge empty sphere in space, not around a star, (empty Dyson sphere) it could form a black hole with all the mass at the outside edge of the sphere?
So, something becomes a black hole when there's too much mass in too small a space.
For a given amount of mass, that's the Schwarzschild radius:
https://en.wikipedia.org/wiki/Schwarzschild_radius
Any object whose radius is smaller than its Schwarzschild radius is called a black hole.
A Dyson sphere would need to avoid collapsing its matter into something smaller than the Schwarzschild radius; if it did, then it would become a black hole. If they don't collapse, then no.
I don't know how Dyson spheres are supposed to avoid gravitational collapse.
goes looking
Okay. Looks like what they do is to basically consist of a bunch of solid satellites that are in orbit but don't collide. They aren't actually a single solid object; the name is something of a misnomer:
https://en.wikipedia.org/wiki/Dyson_sphere
Since Dyson's paper, many variant designs involving an artificial structure or series of structures to encompass a star have been proposed in exploratory engineering or described in science fiction, often under the name "Dyson sphere". Fictional depictions often describe a solid shell of matter enclosing a star β an arrangement considered by Dyson himself to be impossible.
Dyson did not detail how such a system could be constructed, simply referring to it in the paper as a 'shell' or 'biosphere'. He later clarified that he did not have in mind a solid structure, saying: "A solid shell or ring surrounding a star is mechanically impossible. The form of 'biosphere' which I envisaged consists of a loose collection or swarm of objects traveling on independent orbits around the star".[6] Such a concept has often been referred to as a Dyson swarm;[7] however, in 2013, Dyson said that he had come to regret that the concept had been named after him.[8]
A single-solid-piece dyson sphere isn't possible with any known material; even if it was spinning to neutralize its weight at the equator the poles would still need to support their own weight.
...actually that isn't strictly true only in the sense that we're used to thinking about Dyson Spheres. An extremely light-weight sphere could be supported by the light of its own star, like a solar sail. Relatively small habitats could be periodically hung from the surface, supported by a root system of thin supports spreading into the light-weight sail. (Did I just invent an original setting?)
The common solution isn't a solid sphere, but a "Dyson Swarm"; originally thought of by Freeman Dyson himself. Instead of one solid object it's a myriad of smaller objects orbiting so densely that 100% of the star's energy output is captured and processed before radiating into space.
But a solar-system-sized sphere of gas can't do that, because you can't keep the orbits of the gas from smacking into each other.
We would all be deaf by the sound of the sun.
that's roughly a protoplanetary disk, what it's like before new planets form! jupiter's mass is 95% hydrogen-helium atmosphere with a core of ice and metals. because the solar system already has planets, though, we'd expect the ones currently here to "sweep" up the gas along their orbits in a fairly timely manner (jupiter's year is 12 earth-years). if the gas is spinning at about planetary speeds, most of the gas will gradually be pulled out of solar orbit and into planetary atmosphere, so basically all the planets will become gas giants (or possibly new dwarf stars! i haven't done the math). depending on how far out your protoplanetary disk goes you might need new planets form in the outer regions, past the regions where existing planets have formed. expect orbits to get really fucked up due to new gravity dynamics.
so for your questions:
A: yes, you should have enough air pressure to leave orbit in a plane, which is great to flee the planet because the new solar atmosphere will immediately plunge earth into an ice age for a few years as it first blocks most of fhe solar radiation, and then gradually heats up. the solar atmosphere wind dynamics will also fuck you up in a way that the dying Earth's scientific computing will struggle to help with, especially when all satellites burn up in air and fall to the surface
B: (1 AU / the speed of sound) = 5000 days. the distant, ominous howl of a vengeful sun will be the least of your concerns as the nations of earth turn violent in a desperate attempt to save some last trace of human civilization
C: a megacyclone, yes! a beautiful spiral as each planet sweeps up the protoplanetary gases to swell to gas-giant size or dwarf star status. perhaps some day the light of five suns may shine on Earth again, but all traces of what once was will be sunk under five thousand kilometers of a liquid nitrogen sea. in one possible delusion, the billion-year descendants of the last earthlings will live in orbit of a still-molten rock so far past the kuiper belt that the five stars of Sol look like a bright-hot constellation instead of the core of its orbit
D: at some point, yes! for a brief moment the pressure will be unchanged as the solar atmosphere orbits the sun instead of pressing on the earth. perhaps some would be wise enough to realize that the sudden dimming of the sun - eight minutes as it turns to a dull, occluded, sky-colored haze, as if it had just melted away - foretold an imminent disaster. those bright minds would struggle to be heard amid a hundred other apocalyptic visions, because who would believe the sudden, impossible appearance of so much mass? but maybe some would have the sway and the speed to take their calculations to an appropriately powerful spaceplane, or a convenient tanker aircraft, and set off before the earth's mass doubles in a year, then doubles again, like a snowball of oxygen rolling around in the deepening winter.
perhaps some would be wise enough to realize that the sudden dimming of the sun - eight minutes as it turns to a dull, occluded, sky-colored haze, as if it had just melted away -
Huh. If it all snapped into existence, it'd catch the light traveling through space, at that moment. So Earth might briefly get brighter? The dark side obviously would, as Rayleigh scattering turns our penumbra blue... all the way out to fucking Neptune. On the bright side, at first, it would genuinely be more sky, but-- I don't-- I just cannot wrap my head around how to even model that. The entire solar system would flash as bright as the daytime sky, give or take a couple AU, for like a billisecond. And then that energy would bounce around until it's mostly absorbed, surely. The image of the sun might vanish instantly. Even on Earth I expect most photons do not arrive having dodged the entire atmosphere.
Thinking about modeling this ridiculous hypothetical is going to keep me up tonight.
I've been thinking about this alot, so if we change the scenario to the solar systems collides with a huge cloud of air just drifting in space, we would see the blue sky on the moving interface as the air spreads though the solar system.
It's quite magical in the minds eye.
Gradually gliding into a gaseous cloud that the sun lights up would be genuinely fascinating, but still probably kill everyone. Pros and cons.
... would it affect the northern hemisphere first? I have no idea which direction the solar system actually proceeds.
most everything in the milky way galaxy is orbiting the center of the galaxy clockwise relative to our north*, so we'd probably enter the gas cloud from the side by drifting into it faster than it is moving
*that's orbital north, the direction that's perpendicular to orbit and close-ish to the magnetic north pole (which is tilted relative to the orbit)
Well, it wouldn't change the gravitational field of any given planet so the atmospheres around planets would exist still but they might become more air saturated. The other thing to consider is that since this air would be so far away from the gravitational fields of many planets that it would actually get pulled into the sun over time, increasing the mass of the Sun and further accelerating the collapse of the solar system. By how much I could not tell you, but eventually the extra mass being dumped into the vacuum of space around our solar system would increase the mass of our star.
i love the integral trees aeries so much
The air resistance would probably tear the Earth apart. Keep in mind we're whizzing around the sun at like 3000 MPH. All the planets move at different speeds, so something is getting wrecked by air resistance
I read somewhere once (though I don't remember where) that if the solar system was filled with air that would be enough mass to create a black hole.
A - space travel would be harder. The difficulty with travelling into the solar system is gravity, not the vacuum. You would still need to launch something with enough energy to escape the earths gravity. Aeroplanes are not escaping earth's gravity - they're constantly using fuel to stay a certain distance from the earth's surface but they do not have enough energy/power to reach escape velocity.
So if you filled the solar system with gas you wouldn't fix the gravity problem. What you would do is add more friction which would cause drag on space ships, and slow travel between destinations as well as require even more fuel than present. Once a ship is in space currently, "aerodynamics" is not an issue; it's all about gravity and velocity. Throw in air, and you have new problems in drag, shape and as a result likely fuel consumption to stay on course or reach as far as you want to.
Not exactly. All known means of propulsion are based off of throwing something backwards to propel yourself forwards. In a medium like air, you can grab the air in front of you and thrust it behind you. In space, you donβt have that option, you have to carry all of the propellant with you from the start and canβt get more unless someone brings it with you.