• observantTrapezium@lemmy.ca
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    3 months ago

    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
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      3 months ago

      :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?

      • observantTrapezium@lemmy.ca
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        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).

      • pool_spray_098@lemmy.world
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        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…

    • KillingTimeItself@lemmy.dbzer0.com
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      3 months ago

      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
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        3 months ago

        the light hasn’t reached is yet

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

        • KillingTimeItself@lemmy.dbzer0.com
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          3 months ago

          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
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      3 months ago

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

      • SpacetimeMachine@lemmy.world
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        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
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        3 months ago

        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
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          3 months ago

          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
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            3 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.

  • Ð Greıt Þu̇mpkin@lemm.ee
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    3 months ago

    Every time I see these ultramassive black holes all I see is the megastructure uber planet you can build around them, or if organic life has gone out of fashion at that point, the megastructure uber computer.

    • marcos@lemmy.world
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      3 months ago

      Hard to find enough material to encircle that one.

      Maybe that’s why those “dark matter only” galaxies exist.

      • Ð Greıt Þu̇mpkin@lemm.ee
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        3 months ago

        It would take multiple galaxies of matter to pull the material together, but if you’re planning on building a megastructure of this scale that’s probably not any trouble for you

    • psud@aussie.zone
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      3 months ago

      Look up “the great attractor”.

      The “big crunch” is the (probably incorrect) hypothesis that there’s enough mass to pull the universe into a single black hole - where everything is eaten by black holes, even all the black holes (nothing to do with the great attractor). The big bang in reverse