TGP Scientists, I have a stupid question

Discussion in 'The Pub' started by hogy, Apr 24, 2016.

  1. hogy

    hogy Member

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    The observable universe is an estimated 90 billion light years across, and the Big Bang happened 13.8 billion years ago.

    How does this compute? Did matter spread out from the singularity at a speed faster than that of light? What am I missing? And don't say "a brain". That wouldn't be nice.
     
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  2. 65DuoSonic

    65DuoSonic Member

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    Last edited: Apr 24, 2016
  3. Darby Crash

    Darby Crash Member

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    I don't understand how they say it takes light from the Sun about 8 minutes to reach Earth, but I can see the Sun as soon as it comes up over the horizon?!?
     
  4. lefort_1

    lefort_1 Nuzzled Firmly Betwixt Gold Supporting Member

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    For me, the theory of the Inflationary Epoch ( a very brief section of time) immediately after the Big Bang does the best at answering your question.

    https://en.wikipedia.org/wiki/Inflationary_epoch

    Basically ( if I read this right ... and there is ample room for me eff'n this up)
    the density of matter created quite the warp in space time ..... all that universe stuff packed into such a small space....
    that an outward expansion at near light-speed actually moved stuff across a considerable amount of warped space .... think of climbing up and out of a black hole warp, only a lot steeper than that... anyway, the spread of matter** got to a point where the deep warp in space-time suddenly unfolded pushing matter out much further apart. They got a lot of "inertia" from this sudden expansion and that is seen today in the continued expansion of the universe.

    I'll let the REAL physics nerds clean up the theoretical mess I just tossed out there.
    That's the best I can do.


    **my bad...apparently we were all still just primordial quarks, anti-quarks and gluons at that moment. We got better.
     
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  5. jwfran04

    jwfran04 Supporting Member

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    I'm going to assume this is not a sarcastic question, light travels at a fixed speed so any distance between two objects causes a delay in time before the light that is emitted from it reaches that object (or is reflected by it, for example the moon, but anything you see on earth is reflecting light (other than the few examples of bioluminescence such as certain sea creatures) and that's why you see it). So the light that enters your eye took eight minutes to reach you once it was emitted from the Sun. The Sun "rising" above the horizon is actually the rotation of the Earth rotating into the light that was emitted eight minutes ago, giving you the perception that you see the Sun rise in real time. Not to complicate things further, but if you think about the properties of neurons, we are actually living in the past, be it pretty shortly in the past, but everything you see happened before your brain actually registers it because of synaptic transmission, receptor properties, the cable properties of axons, etc all impart a delay in the signal. Our perception of it is in real time however as our brains essentially accounts for these delays.
     
  6. Powderfinger

    Powderfinger Gold Supporting Member

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    You're seeing what it looked like 8 minutes ago.
     
  7. Darby Crash

    Darby Crash Member

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    But I can see it right away ... just as the Sun is coming up over the horizon.
     
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  8. jwfran04

    jwfran04 Supporting Member

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    Think about it like this, if the Sun stopped emitting light for a day, then started emitting light again the next day, eight minutes would pass before the first photons reached the Earth because light travels at a limited speed.
     
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  9. lp_bruce

    lp_bruce Member

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    I have been a scientist, though not a physicist. I do know that we don't actually know how big the universe is--all we can really talk about is the observable universe. Here is a good (short) explanation.

    http://phys.org/news/2015-10-big-universe.html

    Peace,
     
  10. Pedro58

    Pedro58 Member

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    I think he's yanking your chain.
     
  11. Darby Crash

    Darby Crash Member

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    Then how come I don't just see a black ball where the Sun is for 8 minutes after it rises over the horizon?
     
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  12. jwfran04

    jwfran04 Supporting Member

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    Yep, I get that impression at this point. Try to be nice around TGP...
     
  13. HerrRentz

    HerrRentz Member

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    The light you are looking at is eight minutes old. I'm only a rocket scientist though. Not theoretical physics.
     
  14. ACfixer

    ACfixer Member

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    It's kind of like this... prior to damming Niagara and controlling the flow in the early 1900's, the falls eroded almost 4 feet per year. If the earth is 6 (or 13.8) billion years old, does that mean it eroded 24 billion feet or roughly 4.5 million miles? ;)
     
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  15. Pedro58

    Pedro58 Member

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    And I commend you for it. Take the high road, my friend!
     
  16. jwfran04

    jwfran04 Supporting Member

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    As per the original poster's question, there are a lot of things that are not well understood regarding the Big Bang and the formation of the universe, namely that before and in the very, very early time after the Big Bang (like pico-seconds or less), the laws of physics as we understand them likely do not hold up. If I recall correctly, some scientists believe space-time to be an emergent property after the Big Bang, hence the size of the known universe does not necessarily have to be limited by the age of the universe/speed of light. Therefore, the known universe could theoretically be larger in light years than the age of the universe. In addition, the Big Bang theory is just that, a theory, meaning that while many pieces of data point to the Big Bang as the creation of our universe, it's possible that it is wrong/incomplete and another theory/force could explain how the universe was created.
     
    Last edited: Apr 24, 2016
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  17. HerrRentz

    HerrRentz Member

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    The Falls have only been in existence since the end of the last North American glaciation (Wisconsin) after the formation of the Great Lakes.
     
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  18. Moxsam

    Moxsam Member

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    Yes and you sure know a lot about bears and tigers too.
     
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  19. Moxsam

    Moxsam Member

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    What about when it sinks into the horizon at sunset? That's called the Speed of Dark. It's slightly slower than light but more evil. I learnt that in Rocket Surgeon school.
     
  20. Peteyvee

    Peteyvee Premium Platinum Member

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    In the case of @lp_bruce ,being that he's a Detroit native and still lives there, I'd say he knows a lot more about Lions, Tigers, Pistons and Red Wings than the da Bears...
     

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