this post was submitted on 08 Sep 2024
27 points (96.6% liked)

No Stupid Questions

2315 readers
2 users here now

There is no such thing as a Stupid Question!

Don't be embarrassed of your curiosity; everyone has questions that they may feel uncomfortable asking certain people, so this place gives you a nice area not to be judged about asking it. Everyone here is willing to help.

Reminder that the rules for lemmy.ca still apply!

Thanks for reading all of this, even if you didn't read all of this, and your eye started somewhere else, have a watermelon slice 🍉.

founded 2 years ago
MODERATORS
[email protected]
[email protected]
27
Filling the Solar System with AIR - What would happen? (hackertalks.com)
submitted 2 months ago by [email protected] to c/[email protected]
27 comments fedilink hide all child comments
 

Let's suppose we could dump enough "breathable" air (whatever that means for humans) into the solar system that it filled the spaces between planets.

What would happen?

A - I imagine it would then become possible to fly airplanes between planets, perhaps balloons? Would space travel become easier or harder?

B - According to another lemmy post, we would start to hear sound waves from the sun (A constant jackhammer sound - delightful)

C - Each each planet become the center of some mega cyclone (like the Jupiter storms, but bigger)?

D - At some point the air above us wouldn't be pushing down onto the earth at sea level, could we survive the additional pressure?

you are viewing a single comment's thread
view the rest of the comments
[–] [email protected] 10 points 2 months ago* (last edited 2 months ago) (2 children)

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.

[–] [email protected] 2 points 2 months ago* (last edited 2 months ago) (2 children)

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?

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 100–400 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 (± 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* (/ˈsædʒ ˈeɪ stɑːr/ 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 5.6° 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 4.297±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.

[–] [email protected] 1 points 2 months ago (1 children)

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?

[–] [email protected] 2 points 2 months ago* (last edited 2 months ago)

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 – 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]

https://old.reddit.com/r/AskScienceFiction/comments/zqg6e/is_a_dyson_sphere_actually_possible_or_would_it/

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.

[–] [email protected] 2 points 2 months ago* (last edited 2 months ago) (1 children)

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 × 10^45 erg per second (erg s−1) and a total radiated energy between 9.7 × 10^52 erg to 1.5 × 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 (M☉).

Subrayan et al. originally interpreted it to be a tidal disruption event between an SMBH (~10^8 M☉) and a massive star (~14 M☉).[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 M☉),[6] onto an SMBH (>10^8 M☉).[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.

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.

[–] [email protected] 2 points 2 months ago

I’d guess that we’d probably wind up turning ourselves into the largest explosion that humanity has ever observed in the universe.

With front-row seats.

[–] [email protected] 7 points 2 months ago (1 children)

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.

[–] [email protected] 6 points 2 months ago

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.