this post was submitted on 28 Sep 2023
337 points (98.8% liked)

Technology

60073 readers
3459 users here now

This is a most excellent place for technology news and articles.


Our Rules


  1. Follow the lemmy.world rules.
  2. Only tech related content.
  3. Be excellent to each another!
  4. Mod approved content bots can post up to 10 articles per day.
  5. Threads asking for personal tech support may be deleted.
  6. Politics threads may be removed.
  7. No memes allowed as posts, OK to post as comments.
  8. Only approved bots from the list below, to ask if your bot can be added please contact us.
  9. Check for duplicates before posting, duplicates may be removed

Approved Bots


founded 2 years ago
MODERATORS
 

Scientists confirm that the first black hole ever imaged is actually spinning::The first black hole humanity has ever imaged has also provided us with what researchers are calling "unequivocal evidence" that black holes spin.

you are viewing a single comment's thread
view the rest of the comments
[–] [email protected] 5 points 1 year ago (5 children)

Does the black hole spin? Or does the stuff outside the black hole spin? πŸ€”

[–] AbouBenAdhem 20 points 1 year ago (1 children)

The black hole and the stuff outside it constitute a single system, and within that system, angular momentum is conserved. So as objects cross the event horizon, their angular momentum is transferred to the black hole.

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

Well.... does it? If all the stuff falls in and only the volume remains, who could say that it's spinning? How could you detect it?

[–] AbouBenAdhem 12 points 1 year ago* (last edited 1 year ago) (2 children)

For one thing, the size and shape of the event horizon change depending on the black hole’s spin.

[–] Smokeydabear94 3 points 1 year ago (1 children)

What would happen if one were to stop spinning? Could one even stop spinning?

[–] AbouBenAdhem 6 points 1 year ago

Yesβ€”it’s called the Penrose process.

[–] [email protected] 1 points 1 year ago (1 children)

I see. Thank you. So, you can use light to infer the mass, and then the volume information to infer the spin? Easy enough.

[–] AbouBenAdhem 3 points 1 year ago* (last edited 1 year ago)

That would be a general method, if we were close enough to observe the shape of the event horizon (which we aren’t).

The article is describing another way, which only works in this case because the black hole is precessing so extremely that the changing axis of rotation is frame-dragging the polar jets along with it.

[–] Fungah 1 points 1 year ago (1 children)

I thought nothing actually crossed the event horizon and was essentially frozen approaching a complete stop in time in a kind of 2f representation of 3d reality until it slowly leaked out trillions of years later as hawking radiation?

[–] [email protected] 0 points 1 year ago

From an outsider's perspective, you would see an object approach and then freeze. It would red-shift dimmer until it disappeared. From an in-falling perspective, I don't think you'd notice anything at all.

[–] scarabic 6 points 1 year ago

Isn’t most everything spinning? Seems like having zero angular momentum would be rare and remarkable. I’m not even sure how exactly to define zero momentum in terms of reference frames.

[–] tdawg 2 points 1 year ago (1 children)

If you're asking that then you first need to ask what the distinction between the two is. and further does it even make sense for one to spin and not the other

[–] NewNewAccount 1 points 1 year ago (1 children)

Is there not a distinction? I assume the singularity at its center has different properties than the matter outside of that point.

Note: I have a rudimentary understanding of what black holes and their components are.

[–] Telodzrum 1 points 1 year ago

Even if there is heterogeneity inside the system, that does not indicate severability or that the whole system is made up of smaller constituent systems.

[–] [email protected] 1 points 1 year ago (1 children)

It's in space and everything is relative, how do we know *everything else" isn't just spinning around the black hole? πŸ€”

[–] [email protected] 0 points 1 year ago

Because that would require a centripetal force on everything else, which obviously isn't the case.