this post was submitted on 10 Aug 2024
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Science Memes

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[–] observantTrapezium@lemmy.ca 6 points 3 months ago (3 children)

Astrophysicist here. Yes, space is crazy, but interesting things to keep in mind:

  1. The size of a star is determined by something called the photosphere. With those extremely massive stars, you can be hundreds of millions of kilometres "inside" and not yet know it.
  2. Similar story with supermassive black holes, from the perspective of an astronaut falling in, they wouldn't really be able to tell when they cross the horizon because the tidal forces there are very small (they will inevitably fall towards the centre and get spaghettified at some point)
[–] shneancy@lemmy.world 1 points 3 months ago* (last edited 3 months ago) (2 children)

:0 how can you be inside a star and not know it? I thought they all had a surface like our Sun

second question, would you even feel the spaghettification? Would the signals from nerves be able to travell up to the brain?

[–] pool_spray_098@lemmy.world 1 points 3 months ago

Right? How can you not know it?

Hmm, am I in the star yet? I mean my body is now made of million degree hot plasma, but I'm still not sure....

[–] observantTrapezium@lemmy.ca 1 points 3 months ago

See my response below to Captain Aggravated about how dilute those large stars are.

It's an interesting question whether anybody would actually feel spaghettification 😁 I actually don't know. You can use physics to calculate the proper time derivative of the tidal forces, but you need biology to define the start (and end...) of the process. My intuition says that it probably happens too fast, so once the tidal forces are strong enough to be perceptible, they grow strong enough to rip you apart before you realize (again, just a hunch).

[–] KillingTimeItself@lemmy.dbzer0.com 1 points 3 months ago (1 children)

as a non astrophysicist, or just a non astronomer in general. it weirds me out every time i remember that there is literally a part of the universe that apparently exists, of which we will never be able to see, because the light from that part of the universe, quite literally hasn't reached us yet.

The observable universe is inconceivably massive. But it just keeps going.

And to think it's not an improbable concept for humanity to recreate the physics behind a big bang in a controlled setting, somewhere down the line from here, is certainly an interesting thought.

[–] psud@aussie.zone 2 points 2 months ago (1 children)

the light hasn't reached is yet

The light will never reach us, space is expanding faster than light between here and there

perhaps some day we will figure out how to travel faster to light, and the metaphorical light will be capable of reaching us. Though thats also another really bizarre fact.

[–] SanndyTheManndy@lemmy.world 0 points 3 months ago (2 children)

What really are gravitational waves? Are they like electromagnetic waves? Do they cause orbital decay? I have so many questions.

[–] SpacetimeMachine@lemmy.world 1 points 3 months ago

I highly suggest you look up PBS spacetime on YouTube. They have an incredible amount of very informative videos on black holes and gravitational waves. As well as pretty much any other astrophysics topic you can think of (and many you can't!)

[–] observantTrapezium@lemmy.ca 1 points 3 months ago (1 children)

They are quite similar to electromagnetic waves, but also quite different. They are produced by masses accelerating (just like EM waves are produced by charges accelerating), and indeed cause orbital decay. But this orbital decay is only important in relativistic systems (so the Earth, which is orbiting the sun at 0.0001 the speed of light, is not going to fall into the sun because of gravitational waves).

[–] psud@aussie.zone 1 points 2 months ago (1 children)

Surely they're more like ocean waves; EM waves are electric and magnetic fields pulling each other up by their boot straps. Gravity waves are distortions in spacetime

[–] observantTrapezium@lemmy.ca 1 points 2 months ago

EM and gravitational waves are seen as analogous because as I wrote, they are produced by acceleration of charges and masses, respectively. The physics behind them is very different (described by Maxwell's equations for EM and Einstein field equations for GW), but all systems that have waves in them (including sound in the air, waves on the surface of water etc.) can be approximated as linear for small perturbations, which means that they satisfy the wave equation at that regime.