Why the sky is dark in the night

Discussion in 'Astronomy, Exobiology, & Cosmology' started by The God, Mar 23, 2016.

  1. river

    Messages:
    17,307
    Not really
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. paddoboy Valued Senior Member

    Messages:
    27,543
    The best example of empty baseless rhetoric this forum has seen for a long while.
    Still, when we consider that these science sites are nothing more than cesspools--every single one of them. they do not pertain to the actual work in the science sectors. they do not contribute anything too actual science. they are simply places for the want-to-bes and the mentally disable to play at(while endlessly insulting actual scientist and science within the same moment), nothing more.
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. paddoboy Valued Senior Member

    Messages:
    27,543

    Please Register or Log in to view the hidden image!


    Who do you believe you are trying to convince?
    You're on a remote science forum my dearest friend, that languishes on a tiny sliver of cyber space and the real experts that count do not even recognise you.

    Please Register or Log in to view the hidden image!

     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. river

    Messages:
    17,307
    padday boy ; you see the full magnetic spectrum ; now what ?
     
  8. paddoboy Valued Senior Member

    Messages:
    27,543
    Only to someone like yourself that accepts the answer put tic at post 8.
    The usual ways of cranks: That has already been explained.....let me say again.......
    For the first 380,000 years before temperatures had dropped sufficiently for electrons to couple with atomic nuclei, the Universe was opaque with just plasma and photons unable to travel.
    After the recombination the light [brightness] was released for want of a better word] and we still see that today as the CMBR at a temperature of 2.7K

    Yep they all fit together like a hand in a glove.....although we have no certainty about the finite nature of the universe. Not that it makes any difference to olber's paradox which is not a paradox.
    Nonsense and unsupported claims. Some redshifts are quite large, as is the Universe.
    The usual maybe's, perhaps's
    You need to realise that galaxies at such large distances, near the edge of the observable universe, are in time, going to be beyond the observable universe.
    In fact a few hundreds or so billion years hence, no galaxy external to our local region will be visible. We call it the DE factor.
    More rubbish: Ever heard of WMAP?
    Ever heard of the accelerating expansion rate that WMAP discovered?
    So, no, in the long distant future, our observable universe will be just our own merged local group and all distant galaxies shifted beyond the observable horizon.
    See previous correction of your nonsense.
    It's not surprising you consider it incomplete when you have misunderstood the most basic assumptions and data from recent times.
     
    Last edited: Mar 25, 2016
  9. river

    Messages:
    17,307
    padday boy ; you see the full magnetic spectrum ; now what?
     
  10. paddoboy Valued Senior Member

    Messages:
    27,543
    http://www.smithsonianmag.com/magazine/what-does-future-universe-hold-180947977/?no-ist

    If the size of the universe were to remain unchanged, the mutual gravitational attraction among galaxies eventually would cause all of them to merge together. But as we’ve known ever since the astronomer Edwin Hubble’s 1929 discovery, the universe is expanding and galaxies, on average, are moving farther apart. Throughout much of the 20th century, the big question in cosmology circles was: Is there sufficient mass in the universe to enable gravity to halt this expansion? Or will distant galaxies continue to move apart, slowing down but never quite stopping?

    Then came the 1998 discovery that presented a third, unforeseen option: The expansion of the universe is not slowing down, as any sensible universe should be doing, but speeding up. We now know that about 70 percent of the energy of the universe resides in empty space, though we don’t have the slightest understanding of why. This “dark energy” acts as a kind of cosmic antigravity—empty space appears to produce a repulsive force, which is the opposite of the attractive force exerted by all forms of matter. These two competing forces have affected the expansion of the universe since the aftermath of the Big Bang. But as the universe has expanded, the density of matter has decreased while the amount of dark energy has remained constant. And as the braking effect of gravity has diminished, the expansion has accelerated. If dark energy continues to dominate, the most likely outcome is more dismal than any of the scenarios previously envisaged. The current expansion will continue forever, gaining speed, so that all the galaxies we now observe, 100 billion or so of them, will one day disappear beyond our ability to detect them. Our galaxy will be alone in the visible universe. And then, once the stars burn out, the universe will be truly cold, dark and empty.




    Read more: http://www.smithsonianmag.com/magazine/what-does-future-universe-hold-180947977/#oBZSbeb3lbxvL2IG.99
     
  11. river

    Messages:
    17,307
    So implication is ; that the distance between any star and galaxy has increased.

    Has this happened within our own galaxy then ?
     
  12. river

    Messages:
    17,307
    Not so has it pad .
     
  13. paddoboy Valued Senior Member

    Messages:
    27,543
    No, not within our own galaxy....nor within our own local group of galaxies....nor within our cluster:
    The mass/energy densities within isolated areas, and consequently gravity, is decoupled from the overall larger scale expansion of the Universe.
    Imagine a fish swimming at 10kms and hour [spacetime expansion] upstream against a current of 12 kms and hour [gravity of local group]
     
  14. river

    Messages:
    17,307
    Why does this make sense to you. ?
     
  15. paddoboy Valued Senior Member

    Messages:
    27,543
    Because [1] We are familiar with the force of gravity....It is attractive.
    We have a couple of decades ago, discovered [2] an acceleration on the expansion rate that we put down to DE: a force opposing gravity emanating from spacetime itself: Gravity wins over smaller denser regions...DE wins over larger less dense scales.
    Now tell me, what makes sense to you?
     
  16. river

    Messages:
    17,307
    So you think in terms of the Universe as gravity based ?
     
  17. paddoboy Valued Senior Member

    Messages:
    27,543
    I think of the Universe as the data and evidence tells me...and am prepared to modify as new data dictates.
     
  18. river

    Messages:
    17,307
    I don't think your capable of modifying your thinking at all.
     
    Last edited: Mar 25, 2016
  19. Daecon Kiwi fruit Valued Senior Member

    Messages:
    3,133
    Well we know it isn't plasma/electric based.
     
  20. Russ_Watters Not a Trump supporter... Valued Senior Member

    Messages:
    5,051
    When everyone around you has problems, self awareness should make you re-evaluate whether those problems are coming from everyone around or are coming from you.
    Yes. What it doesn't say is what those issues are, much less provide references to those issues (and you still haven't provided the references).
    Since this doesn't affect us now, I don't see why it is an important question. I'm not sure if anyone has ever bothered to answer it and I see no reason to try.
    [edit] Thinking about it more, what you are looking for is a graph of the universe's temperature over time. I bet someone has done the calculation and I suspect you could find it if you wanted to.
    I offered you a simple method for doing the calculation yourself in post #28. You haven't attempted it yet. I see no reason why I should do your work for you. But for the record, there is a thread around here somewhere where I patiently tried to walk someone through the calculations for a month. You can google for it and see the calculations there.

    My suggestion to you is that if you really want to learn about the calculation, you should focus on just that one thing until you have it figured out.
     
    Last edited: Mar 25, 2016
  21. Russ_Watters Not a Trump supporter... Valued Senior Member

    Messages:
    5,051
    Har, Har!!!!!!!
     
  22. river

    Messages:
    17,307
    How so .....
     
  23. Sarkus Hippomonstrosesquippedalo phobe Valued Senior Member

    Messages:
    10,359
    Consider me to be in nitpicking mood.

    Please Register or Log in to view the hidden image!


    The "Observable Universe" currently has a radius of c.47 billion LY, not c.13.8 billion (or whatever the current estimate is for the lifetime of the Universe).
    The observable universe is effectively the maximum size of the universe that contains all the objects whose past is currently observable by us. An object who emitted a photon 13.8 billion years ago (ignoring CMBR, recombinationetc) that is now just reaching us would now be c.47 GLY away.

    The "Hubble volume" is the volume the edge of which is expanding away from us at c.
    This volume is c.14.5 billion LY radius at present, I believe (slightly larger than the age of the universe).

    However, there is also the cosmic event horizon, which is c. 16-16.5 LY radius, which is the furthest away an object can be at this precise time such that light emitted from it will ever reach us. Beyond this radius its current and future activity is forever outside our ability to observe.

    Objects currently between the c.14.5 GLY and the c.16.5 GLY can emit photons that we could still eventually observe, as those photons could eventually move inside the Hubble volume.

    End of nitpicking

    Please Register or Log in to view the hidden image!

     
    paddoboy likes this.

Share This Page