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I Spacetime and effects of being super close to the Sun

  1. Sep 15, 2016 #1
    I have been wondering about space time and how it works like satillites putting corrections in there clocks by a few nano seconds a day because of gravity or lack of it!! But I have also wondered about the effects of being super close to the sun and time that we observe there looking back at earth would it look like the earth was in fastforward?

    But then I wondered what would something like a super black hole look like looking back at the rest of the galaxy somethings that's the mass of trillions of stars could a earth year in the centre of the Galaxy be millions or more on the outer of the Galaxy?
     
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  3. Sep 15, 2016 #2

    mfb

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    The difference is tens of milliseconds per day. That is not really "fast forward".

    The black hole doesn't have to be massive. If you find some way to hover (!) close to the event horizon (where our best guess how to do so is "magic"), you would indeed see the rest of the universe running faster.
     
  4. Sep 15, 2016 #3
    So does that really mean that if you lived
    So lets say that if we lived in the middle of the Galaxy the light from the centre of the Galaxy would move slower well appear to? And the the light from the outer of the Galaxy would appear to be moving much faster?

    And let's say if your saving seconds on the Suns surface per 24 hours spent there that basically mean that your saving years per 24 hours spent at the centre of the Galaxy that being the same gravity of all the stars combined in our Galaxy?!?
     
  5. Sep 15, 2016 #4

    mfb

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    I don't understand that question. Which light where?
    Light always moves at the speed of light. The passage of time can happen at different rates for different observers.

    Distance to the object matters. At the center of the galaxy you are far away from the sun, for example. Time dilation "somewhere close to the galactic center" is still tiny - similar to what you have at the surface of sun, maybe a bit more. You really have to get close to neutron stars or black hole to have a notable effect.
     
  6. Sep 15, 2016 #5
    I know light doesn't change speed... I'm being super fair fetched!! I'm talking about let's say a tennis ball is moving at the the same speed it can't slow down like light straight towards the gravitational pull something that's makes a massive bend in space time. If you looked from outside the tennis ball would seem to be slower as space time played its bit? But being on centre ok the tennis ball would appear to be coming a lot quicker?

    If that makes sense?
     
  7. Sep 15, 2016 #6

    mfb

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    Now I understand your question even less.
     
  8. Sep 16, 2016 #7
    @Justawildwonder In English there are punctuation, grammar and syntax rules. If you want anyone to understand you, you have to be clear, otherwise you're wasting everyone's time, including yours.
     
  9. Sep 16, 2016 #8
    I think @Justawildwonder is wondering about the perception of distant objects depending on the intensity of gravity <-> dilation of space-time.
    Not that I really understand how this works, but higher gravity means "denser" space, and consequently slower time. So yes, if an observer very close to a black hole would watch "in real time" a tennis ball moving much farther away, the ball would appear to move faster than it actually is.
    Then again, I might be riding my horse completely backwards....
     
  10. Sep 17, 2016 #9

    I wonder now that if the reason why we can't see black holes is because that the light is moving to slow at our point of view to see.. but it be crazy if it was true. Be like 9.4 years on earth to 1 second at the black hole.. if the math is correct?
     
  11. Sep 18, 2016 #10

    mfb

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    No.
    Where did you get this number from? It looks completely arbitrary. It also doesn't make sense.
     
  12. Sep 18, 2016 #11
    Mercury has an orbit that seemed peculiar and inexplicable before GR.
    GR was able to account for that being because of Mercury's close proximity to the Sun.
     
  13. Sep 20, 2016 #12
    This is just a thought that popped into my head (these may not be in the correct order). We used to believed the sun rotated around us. We believed the earth was flat. Then we discovered planets and realized we all rotated around the sun. Then we learned the earth was round. Then we discovered universes and deep space. Is it possible the universes, themselves, revolve around a central entity? Something we can't see or haven't found yet?
     
  14. Sep 20, 2016 #13

    mfb

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    The round shape of the Earth was known long (~2000 years) before there was clear evidence that the Earth orbits the sun.
    There is no place for anything "central" in our universe.

    Please read our forum rules on speculations.
     
  15. Sep 20, 2016 #14

    Chronos

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    Consider an observer falling into a black hole from a stationary position outside the event horizon. Initially time is passing at a normal pace then the observer accelerates toward the singularity [although always at a speed less than c]. Interestingly enough, this causes the external universe to look redshifted. Photons from the external universe struggle to catch up with the infalling observer, so it appears the universe ages more slowly than for a stationary observer! A remote observer also sees the hapless infaller redshift upon approaching the EH, so it turns out neither observer gets to view the others future! The only way to see the distant future of the universe is to hover stationary very near the EH, which is a physical impossibility. Even light cannot maintain a stationary orbit wrt to a non-rotating black hole at a distance less than its photon sphere [1-1/2 times its Swarzschild radius].
     
  16. Sep 21, 2016 #15

    mfb

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    It is "only" an engineering problem. With a powerful rocket you can hover close to the event horizon - in theory.
     
  17. Sep 21, 2016 #16

    Chronos

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    A rocket capable of light speed? That would be a pretty amazing piece of engineering.
     
  18. Sep 21, 2016 #17

    mfb

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    No. The rocket just needs a strong acceleration. A higher acceleration allows to hover closer to the event horizon. The speed stays zero for reasonable definitions of speed.

    Also note that light can escape if it is emitted close to the event horizon (closer than the photon sphere) - if it is directed outwards.
     
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