Is the Universe "Shrinking?"

Discussion in 'Science and Nature' started by tHe LoNLy StOnR, Apr 13, 2013.

  1. First off, we know that the universe is expanding, as is confirmed by high school physics my foggy brain fails to remember (something about red shift), and I don't intend to start a ridiculous argument about how the universe isn't shrinking, so I'll clarify what I meant by the thread title.

    If we assume that our current scientific knowledge is correct, would there be a point in time where the universe will devour itself? This might have brought up by some other scientist, and if so, be as kind as to tell me who it is and his proposed theory.

    TL;DR

    Matter cannot be created or destroyed, it can only be sucked up by the ever growing number of blackholes that populate our universe. ie. The universe is eating itself, and soon it will be stuffed.
     
  2. THe problem with what you are saying is the black holes do not suck things in. They act just like the sun or any other large body. If the sun were replaced with a black hole of equal mass, Earth would continue in its same orbit and not get sucked in.

    As you mentioned, the universe is expanding - or rather, the space in the universe is expanding (dont picture the universe as a firework expanding outward into space, because it IS expanding space, not expanding into space).
    We also know this expansion is accelerating. Two main factors are used when discussing the fate of the universe.
    1. Matter density, the actual density of matter divided by the critical density. the critical density is the minimum density that allows the universe to continue expanding and not collapse back in on itself in a reverse big band scenario. Through various techniques that i dont understand, we can calculate the actual density and we know the mathematical expression for critical density (it depends on the Hubble term, but we've narrowed that down too). We basically know that the current matter density is around 0.27. When it is >1, we have a reverse big bang, <1 we have expansion forever.

    The otehr parameter came out of necessity because matter with mass has gravity and gravity will slow the expansion and want to bring it to a stop. When it was realized the expansion is accelerating then th new term Energy Density (dark energy) had to be added to account for something accelerating the expansion since we know matter exists and gravity only slows it down.

    Also, the current understanding is the universe is flat, geometrically. This means that matter density PLUS energy density is equal to 1. In this scenario, the universe expands and the expansion initially slows down due to gravity, but then speeds up due to dark energy. This means the energy density parameter is around 0.76.

    Sorry, I digress.

    The idea that blackholes will eat everything is fundamentally wrong. Because the universe is flat, the two fates are Heat Death (maximum entropy) or Big Rip (expansion is so large that it overcomes gravity, electromagnetic, and strong/weak nuclear forces and tears everything apart).
    Scientists can actually sorta predict the time scales for these two fates.
     
  3. Yeah, the universe is either going to freeze go into a deep freeze through dark energy's expansion or it might also collide with another universe which would also end it.
     
  4. When two galaxies collide they aren't destroyed. Why should the universe be different.

    What if they just merge?
     
  5. #5 Tomato Dog, Apr 14, 2013
    Last edited by a moderator: Apr 14, 2013
    When 2 galaxies collide they aren't destroyed because the distance in between the stars and planets is too vast. If another universe collides with ours what happens, would depend on the traits of that other specific universe or even our own universes traits. Don't take my word on this though. Although they have ideas, I believe physicist don't have an entire certainty around what happens when 2 universes collide yet. I think they believe that's what started the big bang?
     
  6. If the universe is expanding what is it expanding into, that's all I heard
     

  7. By definition, universe is all that exists.

    So how can there be two of 'all that exists'? lol



    All I have to ask if wtf is outside of reality/nature that it's expanding into in the first place..?
     
  8. I'm a firm believer of the multiverse theory, I'm using the term 'universe' to describe all that exists inside our universe, there is no other word to get the point across unless there has been another term put into definition, please let me know.
     
  9. is universe isnt expanding into anything, the space inside of it is itself expanding.

    theres no real analogy to compare it to in our every day lives so its hard for people to wrap their brain around.
     
  10. It's clear that I have been getting pretty eroneous info about our universe, and running with it. I'll try and read up some more, but I'm sure, a couple days of reading won't get me on the level of the academics lurking these forums, but at least I'll be able to follow what they say ... somewhat. :D
     
  11. #11 Deleted member 538806, Apr 17, 2013
    Last edited: Apr 17, 2013
    One analogy to use is a map with a distance scale, let's say one inch on the map equals one mile on land. If we slowly change the scale to where one inch equals two miles, the distances we would measure between cities would appear to be greater and things would have appeared to expand. This is exactly what we mean by scale factor and comoving distance. The comoving distance doesn't change with time like the distance between two cities, but the scale factor does!

    The problem with my analogy is that in the universe, comoving distances do not correspond to physical distances. We always have to multiply the comoving distance by the scale factor to get a physical distance.
     
  12. The ancient Sanskrit Vedas describe that the universe grows outward into more diversity and creation but eventually comes back to one point to just repeat the cycle again. This is also a part of the Hermetic principle of Rhythm “Everything flows, out and in; everything has its tides; all things rise and fall; the pendulum-swing manifests in
    everything; the measure of the swing to the right is the measure of the swing to the left; rhythm compensates.”

    btw read this whilst listening to the third song in this album [ame]http://www.youtube.com/watch?v=3wn8igSeiCI[/ame]

    actually read everything whilst listening to this
     
  13. A valid picture of the universe is an oscillating system. It is possible that billions of years in the future, expansion of spacetime will stop and the spacetime structure will begin to collapse inward. Then, when the "big crunch" is finished there will be singularity similar to the universe at the time of the big bang. In a sense, this picture of the universe shows it expanding, and contracting forever.

    source: theoretical physics professor
     

  14. when you say that our universe may collide with another universe are you referring to the universe as we imagine it as a result of the big bang or the our solar system in particular? I just cant imagine another universe other than possibly vacant space existing prior to the big bang for there to be more than one for a potential collision to occur. Unless you mean that potentially multi universes that co exist in dimensions beyond our understanding.
     
  15. #16 Tomato Dog, Apr 19, 2013
    Last edited by a moderator: Apr 19, 2013

    [​IMG]

    Picture, two 3 dimensional worlds stretching off to infinity but separated from each other by a tiny gap (between the 2 squares in the figure.)

    The two 3 dimensional worlds are then pulled together by a very weak force, it has to be. Otherwise the big bang would occur too quickly.
    As the rippling 3 dimensional worlds approach closer and closer the force becomes stronger.
    When they collide, the kinetic energy of the worlds is converted into the hot radiation that fills both (the big bang)
    Then as the 3 dimensional worlds move apart again (dark energy), both worlds are filled with the matter and radiation that was created during the collision
    This causes both worlds to expand and cool.
    These cycles usually aren't short (but they also can be) since there's probably an infinite number of these worlds
    Fortunately though in our case, it hasn't been short. Since it's been about 13.7 billion years since the last one.

    they're saying maybe the source of the dark energy then is actually the same source of dark energy we have now, and the universe is going through a cycle of these collisions. Whenever another universe collides with it.

    So you can have a Bang, followed by a normal period of the universe (like were living in today) Followed by a second Bang in our future and so on and so on forever.
    The notion above theorizes that there was always a time, before time.
    (This is the theory of. What was the cosmic singularity?)
     

  16. Seems like the ancient people of the indian subcontinent had this stuff figured out a few thousand years ago.
     
  17. you are a theoretical physics professor or one told you that - because its kinda wrong.

    The average density of matter in the universe is KNOWN to be very close, if not equal to the critical density (WMAP further confirmed this) so we know the Big Crunch is no longer an option.
    Add in cosmological constant/dark energy and it is even further from ever going to collapse, it's going to expand forever.
     
  18. #20 Amias, Apr 20, 2013
    Last edited by a moderator: Apr 20, 2013
    My proffessor told me that. Michael miller, look him up he is awesome! google: "michael miller cern" because there are many michael millers

    but anyways: Yes, the more accurately we measure the mass density the closer it becomes to the critical point, so it is likely that the universe will not have a big crunch but not out of the realm of possibility.

    I don't think the cosmological constant is a particularly good indication of anything, it is basically just an adjustable parameter to eistein's field equations. and i have serious doubts about dark energy for that reason. The fact that the model we made tells us that there should be something there is not a very good indication the thing exists. there is likely just something we are missing in cosmology.
     

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