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Joined 11 months ago
Cake day: October 17th, 2023
  • ImFrenchSoWhateverBtoAsk Astronomy@academy.garden•Time near the event horizon of a black holeEnglish
    1·
    10 months ago

    If the magic telephone works this way (it’s magic but still obey to physics when it comes to time dilation), then :

    When they approach the event horizon the astronauts will talk slower and slower until they just froze in place.

    So it won’t be “much slower” it’ll be “frozen and in place (almost) forever”

    From the astronauts point of view tho, they’ll see us get old and die in a few milliseconds.

    But at this point we don’t need a magic telephone: this is what would happen with a normal telescope as well.

    (To give you another image let say in a galaxy there’s one super nova each century. When the astronaut is going to get close to the event horizon when he’ll watch the closest galaxy he’ll see it sparkle like a Christmas tree with dozens of super nova each seconds.)

  • ImFrenchSoWhateverBtoAsk Astronomy@academy.garden•Time near the event horizon of a black holeEnglish
    1·
    10 months ago

    “How long does it take for the astronaut to cross the event horizon outside of the gravity” : well if you’re talking about the actual event, and not its image, it happens immediately.

    The thing is : time is relative so the question doesn’t really mean anything.

    Let say you’re the far away observer and you have an impossible magical telephone with face time that doesn’t obey the law of physics and you can talk live to the astronaut. You’re going to see them go into the black hole immediately when it happens. If you look through your normal telescope they look red and suspended forever. In your magical FaceTime they’ll be gone.

    If your question is : for how long the red phantom image will stay visible : a very very long time. Yes some math can be done to calculate that very long time. Yes the math will take into account the mass of the black hole. But it’s going to be a very very long time anyway.

  • ImFrenchSoWhateverBtoAsk Astronomy@academy.garden•Time near the event horizon of a black holeEnglish
    1·
    10 months ago

    Yes the object will fall into the black hole and its mass will be added to the mass of the black hole, and the event horizon will grow slightly.

    From the point ow view of the object falling into the black hole everything will happen at a normal speed. Meaning if it’s a cosmonaut falling he could look at his watch and the watch would perform normally, a second would still pass in a second. If the cosmonaut was heading fast into the black hole, he’ll soon be in.

    From an observer far away tho it will appear like the object gets slower and slower and redder and redder, until it appears to stop in front of the horizon as a totally red image.

    Why ? Because the closer the objects get to the black hole the more the light it emits is dragged by the massive gravitation an attraction of the black hole. The light has to fight a lot to escape the gravity slope. So it’s gets slower and slower and redder and redder. The very last image of the object falling is almost unable to escape the gravity, so the far away observer won’t see it until a very very long time.

    So to answer your question : yes everything falls in and their mass gets added to the masse of the black hole. The persisting red image is just an image (it’s just an illusion if you will).

  • ImFrenchSoWhateverBtoAsk Astronomy@academy.garden•How do we know if we live in a cyclical universe?English
    1·
    10 months ago

    Well that’s just not really true is it !

    It’s like saying we never directly detected quarks so we can’t talk about it. It doesn’t work this way !

    There’s the quantum gravity loop theory that thinks about the universe before the Big Bang - that’s the theory of the big bounce. See Carlos Rovelli et alli

    There’s the theory of the multiverse that is constructed by leading physicists. See Aurelien Barrau et alli

    As for physics inside a black hole there’s again tons of physics on the subject. See Kip Thorne and Carlos Rovelli book “white holes” (that is on the exact topic of space quantification and how it could solve the singularity problem, for black holes and the Big Bang).

    The thing is for simplicity physicists tend to call the visible universe “the universe” so it might have lead you to think that they actually think that nothing existed before “the universe”.

    That’s not true. Same you can hear people say “the universe is 90 billions light years across” they talk about the visible universe. Everybody knows the actual universe is way bigger !

    Anyway 🤗

  • ImFrenchSoWhateverBtoAsk Astronomy@academy.garden•How do we know if we live in a cyclical universe?English
    1·
    10 months ago

    I didn’t came to this conclusion. I’m not smart enough for that.

    But what I did is I read books on the topic. And those books said that in the past the universe was very small and very hot.

    And it seemed that at one point it was so small and so hot that it would form a singularity. That is surely not possible. An infinite density and infinite curvature into a point with no dimension can’t exist.

    So what’s the other possibility? It’s that the universe can be very small and very hot, but not infinitely hot and infinitely small. And when it reaches this limit, it bounces back.

    That’s why lots of eminent physicists are thinking that the Big Bang was actually a big bounce (hence the cyclical part of the discussion).

    And nobody thinks that the Big Bang was a creation of the universe from nothing.

    To make things even more simple : the universe is either cyclical or came from nothing because we know for a fact that it is in expansion (and was very contracted at one point)

    But do you want to actually have a conversation? Or do you just want to be mad at me ?