If i were able to pause time

  1. If i were able to pause time at this instant and travel anywhere in the universe, would the majority of it still be galaxies, like we see today (excluding dark matter and energy)? Take the Hubble deep field. Would the most distant galaxies we see in that picture still be galaxies at this instant in time, or have they most likely disbanded by now (i have no clue if disbanded is the correct word)?
     
  2. jcsd
  3. phinds

    phinds 9,148
    Gold Member

    What you see right now is how it WAS when the light left it. The Hubble Deep Field is of galaxies that emitted the light we see some 12 or 13 billion years ago. If you could instantaneous be at one of them "now", it would have aged by that many years. Some would have likely merged.

    What do you mean "excluding dark matter" ? If there were no dark matter there would not BE any galaxies, then or now.
     
  4. Well when i said "majority of the universe", i was trying to refer to everything that's not dark matter or energy, even though its a small percentage of the total universe, 4 or so percent if I'm not mistaken. Probably a stupid thing to add, i can see how it could be confusing. Ignore that. So at this moment in time, we think that those distant galaxies have merged into fewer, larger galaxies?
     
  5. phinds

    phinds 9,148
    Gold Member

    Some will have merged. Actually, I don't know enough cosmology to know how galaxies age. I would EXPECT them to still be there (other than merging) but again, I'm no expert.

    Our own galaxy is about 13 billion years old give or take a few weeks and it shows no signs of going anywhere any time soon, other than an upcoming merge with Andromeda is a 4 or so billion years.
     
  6. Oh, ok. So one more question. Since there is no center of the universe, do we know what we would see if we were observing from the point of view of one of those distant galaxies?
     
  7. phinds

    phinds 9,148
    Gold Member

    Pretty much exactly what we see from here except that we wouldn't see a Milky Way equivalent unless we were in one of those galaxies.

    This of course means that we would see next to nothing since almost everything we see with the naked eye is IN the Milky Way.
     
  8. Drakkith

    Staff: Mentor

    If we took our Hubble Space Telescope and made observations we would see something similar to what we see already. Billions upon billions of galaxies surrounding us in all directions. If you are inside a galaxy you would also see stars, nebula, etc.
     
  9. Chronos

    Chronos 10,126
    Science Advisor
    Gold Member

    Phinds is correct. If you could magically transport instantaneously to a galaxy 12 billion light years distant, the universe would look like it does from our vantage point - 13.7 billion years old and homogenously filled with galaxies. Of course the star, or whatever you thought you were transporting to, would be long gone since all that stuff would have been on the move for 12 billion years. This is a problem with instantaneous transport. If you instantaneously transported to some apparent location on the moon, the moon will have moved about 1.3 seconds by the time you arrived. How far does the moon move in 1.3 seconds? That gets rather complicated. The moon has an orbital velocity of about 1 km/sec. OK, that doesnt sound too awful, you would only miss your target by about 1300 meters. But that isnt the end of the story. The moon orbits the earth which orbits the sun. Orbital velocity of the earth is about 28 km/sec. And the sun orbits the milky way at about 220 km/sec, and the milky way orbits the local group, and the local group orbits the Virgo supercluster, and so forth. Relative to the CMB, we are hurtling through space at around 600 km/sec. In other words, everything in the universe moves relatively quickly, and in complicated fashion in the mere span of 1.3 seconds. In terms of any absolute coordinate system, there is no telling where you might end up relative to your target on the moon. Depending on how the various directions of movement components conspire to shift things, you might rematerialize hundreds of kilometers below the surface of the moon, miss it entirely, or anything in between.
     
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