I always had a hard time conjuring up an image of how every galaxy in our universe could be moving away from every other galaxy. The balloon analogy did a decent job of doing so by saying that if you drew dots all over the surface of a balloon at equal distances apart from each other with a marker and then blew it up, that every dot on the balloon’s surface would be moving away from each other in much the same way as galaxies do. My question is, being that this is in fact the case and very recently proven to be accelerating away from each other, does this also hold true for all of the stars present within a set galaxy. Are they too all moving away from each other? Or did I just burst the ballon??
Galaxies are gravity wells which generally keep stars within their influence, resisting expansion.
That’s where the balloon analogy you describe loses steam, because if you draw dots on the balloon, they expand also when you inflate the balloon. The analogy works better if you paste dots on the balloon. They retain their original size, but inflating the balloon still moves them apart from each other.
In the short term, the galaxy is stable. But in the very long term, dark energy implies that everything will eventually fly apart to the point that each individual particle will be out of contact with one another.
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Dartmouth physicist Robert Caldwell and his colleagues Marc Kamionkowski and Nevin Weinberg at Caltech have determined that if the supposed dark energy responsible for the acceleration is potent enough not only will the space between galaxies continue to increase but that the galaxies themselves will fly apart as will, at successive times stars, planets, and even atoms and nuclei.
In the short term, the galaxy is stable. But in the very long term, dark energy implies that everything will eventually fly apart to the point that each individual particle will be out of contact with one another.
Er, so explain how, all the observational evidence we have so far shows things, collapsing onto each other - dark matter filliaments causing the formation of galaxies, galaxy groups, galaxy clusters and galaxy superclusters.
A galaxy is essentially a dark matter clump, which has accreted gas, some of which has collapsed further to form stars. Its the gravitational potential of the dark matter clump that keeps the galaxy together; and this has a far greater extent than just the optical stars that we see.
The ‘Big Rip’ may happen in 22 billion years or so, but I think by then, mankind won’t even be around to worry about it.
Isn’t that exactly what Expano Mapcase is saying? That stuff will collapse until we’re well into the dark energy-dominated era. I think that >22 Gyr is what he’s calling “the very long term”.
Humanity might not be around as such, but it may be that humanity’s distant descendants may be concerned about this Big Rip;
Many of the red dwarf stars that make uo our galaxy will still be steadily shining in 22 billion years time,
and there could be vast communities of beings living round those stars; some of which might have migrated outward from the solar System when the sun goes red giant, 5 billion years from now.
It seems likely to me that the Big Rip will destroy a universe full of life.
However, the Big Rip theory is not definitely proved yet (or is it?)
If there is one concept which goes against all notions of thermodynamics it is dark energy- as space expands, the push gets stronger (or so it seems)…
Well, yes. But, what to you and me might be obviously long term, may well not be to a non-astronomer/astrophysicist. That was the point I was trying to make.
Many of the questions asked are answered in the cited articles, but for those who won’t click:
The 22 billion year figure is the “most extreme” scenario. A different value for “w” - the cosmological constant - will produce a longer lasting universe.
Even in this scenario, the Milky Way galaxy will last several times as long as it already has, which is certainly the long term.
Dark energy implies an increasing counter effect to gravity, so the fact that matter accreted in the early years of the universe is not necessarily relevant to what happens in the future.
The Big Rip is not proven and Caldwell himself says “that deciding between this model and the others might be possible in coming years with much better data coming from microwave background, supernovae, and galaxy measurements.”
The OP never asked whether humanity will be around to see it. Whether humanity, descendents of humanity, or any forms of life whatsoever will be around in 22 (or more) billion years is so totally unanswerable that I don’t find speculation meaningful. And the universe really doesn’t give a rip about life.
There isn’t a scenrio science can come up with, so far as I know, that would allow for the perpetual existence of life.
The possibilities:
Big Crunch: The matter/energy density of the universe is enough to halt the expansion triggered by the Big Bang, and all matter eventually gets crushed down to the Plank volume. What’s a little horrifying is the rate of contraction won’t be linear: At first it will seem as slow as stillness, but eventually things will be rushing together so quickly that it would be noticeable on humanly-perceptible time scales, before the matter/energy density was so great that nothing we can conceive of could possibly survive the matter-melting temperatures. That means that whoever is around during the Big Crunch could actually feel it before they’re immolated.
Asymptotic Expansion: The universe approaches perfect topological flatness for all eternity. Galaxies, and eventually stars, get so far away from one another that nothing else is visible in the night sky but endless darkness. What stars and other collections of matter haven’t collapsed into black holes will grow colder and colder until there isn’t enough energy concentrated anywhere to do work (which requires an energy gradient). The lone source of radiation will be black holes, which will emit energy at a barely perceptible rate at first, until their mass is almost completely evaporated; they then will rapidly explode, the final bursts of light and heat the universe will ever see, until the last bit of energy is distributed evenly throughout the endless night. Quantum fluctuations will be the only phenomena, and all possible thought and action will vanish as the zero-point energy is universally achieved.
Big Rip: Basically the same end result as asymptotic expansion, but more horrifying. Everything in the universe begins to speed away from every other thing at an exponential rate. Space expands so quickly that matter is ripped apart. Even quarks won’t be held together, and when all the black holes evaporate, again you’re left with nothing but zero point energy, an no ability to do work. As with the big crunch, to future life forms, because of this non-linear expansion, the change in rate that things are dispersed might eventually be perceptible: No technology we can conceive of will be able to resist the big rip, and it’s possible our ancestors will be able to perceive themselves being torn apart before their very atoms are shredded.
As far as I can tell, the only alternative to creeping extinction or rapid, horrific disintegration, is universal suicide. Luckily, we don’t need to worry about it.
I should admit that it bugged me, a little while after posting in that thread, to realise that the 1997 conclusion I cite wouldn’t take into account dark energy and so there was some scope for looking for a loophole. Not that I believe there is such a loophole: just the opportunity for someone to write a paper/article reassessing the question in the light of current thinking.
Indeed. In fact, the last seminar I went to on dark energy and possible cosmological scenarios (about three weeks ago), suggested a rather smaller value of w than the worst case scenario, and that, using current cosmological simulations, which trace the evolution of the universe, taking w into account, the value of w required would probably not cause a Big Rip.
DISCLAIMER: This is from memory, I can’t find my notes from that seminar, but that is the gist of current (as yet unpublished) research.