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🤔 Black hole myth busted: they don't suck anything in (bigthink.com)

submitted 12 hours ago* (last edited 4 hours ago) by zdhzm2pgp@lemmy.ml to c/science@lemmy.ml

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[–] unexposedhazard@discuss.tchncs.de 33 points 12 hours ago* (last edited 12 hours ago) (3 children)

Eh thats kinda nitpicky. For non physics people "sucking in with lots of force" is good enough to describe "absurdly strong gravitational pull". Its not a myth, its an over simplification.

[–] Ferk@lemmy.ml 9 points 11 hours ago* (last edited 10 hours ago) (1 children)

I think the point the article was trying to make is that "sucking in with lots of force" does not really happen any differently outside the event horizon of a black hole than it would in the proximity of any other star (or object) with the same mass.

So it's addressing the "myth" that being in the proximity of a black hole would inevitably suck you in.. however, odds are that if you are not directly aiming for the black hole, even if you did not resist, you would just end up entering an orbit around it, the same way we are currently orbiting the Sun. Or maybe even be catapulted out of it, instead of sucked in.

The difference would be that past the event horizon you would be torn apart by the space distortion (instead of being cooked alive if it were a star). But theoretically if you can avoid crashing into a star, then you can avoid entering a black hole.

[–] ada@lemmy.blahaj.zone 1 points 1 hour ago

does not really happen any differently outside the event horizon of a black hole

I mean, that's a pretty big caveat, given that strength of the gravitational force in the object was big enough to create the event horizon in the first place

[–] LazerFX@sh.itjust.works 5 points 12 hours ago* (last edited 12 hours ago)

It's exactly the same gravitational pull as the star that previously collapsed... (And I've not read the article (yet), this is just a personal nitpick that I've had for a LONG time).

--edit after reading the article--

In terms of inevitably falling into a black hole, it’s only the material that formed interior to three times the event horizon radius — interior to what’s known as the innermost stable circular orbit (ISCO) in general relativity — that would inexorably get sucked into it. Compared to what actually falls into the event horizon in our physical reality, the purported “sucking” effects are nowhere to be found. In the end, we have only the force of gravity, and the curved spacetime that would result from the presence of these masses, affecting the evolution of objects located in space at all. The idea that black holes suck anything in is arguably the biggest myth about black holes of all. They grow due to gravitation, and nothing more. In this Universe, that’s more than enough to account for all the phenomena we observe.

That summary explains it better than I can.

[–] nous@programming.dev 3 points 11 hours ago (1 children)

I disagree. It is more than just a nitpick. Saying black holes suck things in implies that they are doing something different than any other mass. Which they are not. Would you say a star sucks in stuff around it? Or a planet? Or moon? No. That sounds absurd. It makes it sound like blackholes are doing something different to everything else - which is miss-leading at best. They way things are described matter as it paints a very different picture to the layman.

[–] PlzGivHugs@sh.itjust.works 4 points 11 hours ago (1 children)

Would you say a star sucks in stuff around it? Or a planet? Or moon?

For a star, I absolutely would. For a planet or moon, it depends on the context.

[–] Ferk@lemmy.ml 3 points 10 hours ago* (last edited 10 hours ago) (1 children)

Would you say our planet is currently being sucked in by the Sun? or would you rather say that we are just orbiting the Sun?

Because odds are that if you approach a black hole without aiming directly for it, you might just end up in an orbit around it, not unlike we currently are around the Sun. Or you might even be catapulted out, instead of being "sucked in" in the popular sense.

[–] PlzGivHugs@sh.itjust.works 2 points 9 hours ago (1 children)

In the case of the earth, no, I would say its an orbit. But if the path wasn't circular and instead was describing the sun pulling somthing away from its existing trajectory significantly, then yes, I might describe it as the sun sucking it in. Obviously doubly so if it actually is destroyed by the sun.

[–] Ferk@lemmy.ml 1 points 8 hours ago* (last edited 6 hours ago) (1 children)

Then, under that interpretation, whether a black hole "sucks in" depends entirely on the trajectory you have. I'd argue then that considering all possible trajectories, you are more likely to not be sucked in by the black hole.

The path the Earth traces isn't circular, it's more like it's spiraling forming ellipses around the Sun and progressively getting further and further away from it (so we are actually slowly being pulled out rather than sucked in). If instead of a Sun we had a black hole with the same mass, nothing would change in that respect, since gravity only depends on the center of mass.

The difference (other than the temperature and light) is that a black hole is very very dense so it would be much much smaller. This means you can get a lot closer to it and this is what makes the gravity skyrocket (since gravity relates to the distance squared). With a star, you can't get close enough to its center without reaching first the INSIDE of the star.. and once you are below the surface of the star then the mass between you and the center of the star gets progressively smaller the closer you get to its center (and the mass that's behind you will get higher and higher), so this dampens the gravitational pull.

[–] PlzGivHugs@sh.itjust.works 1 points 5 minutes ago* (last edited 4 minutes ago)

My point isn't that a black hole is unique or anything else of the sort. Heavy objects try to suck in lighter objects around them. The reason I was saying I would only sometimes describe it as being "sucked in" was because that suggests being significantly pulled towards the object, whereas if it is a fairly stable orbit or the object's trajectory being slightly bent, I wouldn't describe it as such (black hole or otherwise). Even with a gas giant, It wouldn't feel wrong to say it sucks in nearby debris.