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Nagging question about inflation of universe

  1. Apr 17, 2003 #1
    I've had a nagging question about the nature of inflation of the universe for some time, something that to me seems intuitive but which I've never seen asked or answered. I recognize the danger of intuitive thinking in modern physics, but hopefully some of the experts here can help straighten me out.

    Essentially, my understanding is that if we take two widely separated cosmic entities, such as galaxies, we observe that they are moving away from one another at a speed proportional to their distance; the predominant cosmological theory is that space between them is expanding, thus causing them to fly apart.

    My question is basically this: how does inflation work on smaller scales? For example, we know that objects within the solar system or atoms in our bodies are held in position relative to one another via gravitational or nuclear forces, respectively. But haven't we concluded that all space expands, and therefore mustn't that also include the space between (or even within) these objects?

    If the answer is yes, which I take as reasonable, my admittedly naive conclusion (and this is where the intuition comes into play) is that, as it inflates, space must "flow" past pieces of matter that are bound in stationary relative position within a system. I could seemingly explain this away by believing that this phenomenon would more or less have no effect on the matter in small systems, but that doesn't appear to hold up because we can easily see the net effect of inflation over the scale of millions of light years between galaxies. It is my assumption that such a phenomenon couldn't have such a large effect on galactic scales without also having some effect on local scales, however small.

    So, what I'm seemingly left with is the idea of a phenomenon that constantly attemps to increase the potential energy of any system of matter by exerting a separative force on pieces of matter, but which is overcome on small scales by the interaction of matter via fundamental forces. Does this make any sense, and if so, how might this phenomenon manifest itself? For example, could it account for discrepancies in orbital observations, or unexpected loss of energy in some systems?

    I suppose that part of my question revolves around the magnitude of inflation--can anyone point me to an equation? Even without this information, it seems to me that this effect would still be non-zero for any spatially separated masses, and thus potentially calculable.

    Thanks for any insight.
  2. jcsd
  3. Apr 17, 2003 #2


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    Greetings !

    Welcome to PF tfast !

    This is an intresting idea indeed. I thought
    about this before too and I wondered if this
    can have some effects on the microscopic
    scale that QM deals with. For example, what
    are the implacations for orbitals in atoms -
    if space expands then the orbitals can not
    seemingly remain stable without some
    adaptation or maybe expansion is part of the
    whole thing in the first place.
    Any expert opinions about such potential
    effects people ?

    Live long and prosper.
  4. Apr 17, 2003 #3
    So your asking why doesnt the space between smaller objects such as atoms and such expand?

    isnt it because there bond is stronger than the expansion of the universe? i can sorta explain what i mean with an example. when to space bodies collide such as galixies isnt the pull of gravity stronger than the expansion of space. so therefor the expansion cannot prevent the objects from comming together. i would think the same would be true on the atomic scale. the bonds are to strong for the expansion to break.
    i would think the expansions effects could only be seen in the vacum of space between two unrelated objects

    i could be terribly wrong tho
  5. Apr 17, 2003 #4


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    The Hubble Constant is ~50 km/s/Mpc (thats mega-parsec). Since one parsec = 3.26 light years, our nearest neighboring star is about 2 parsecs away. So multiply:

    2 pc * 50 km/s/MPC / 1,000,000 pc/Mpc = .0001 or .1 m/s

    Not much expansion betwen us and our nearest neighbor - unobservably small. Our solar system is even smaller - about 12 billion km. (.000389 pc). So multiply again:

    .000389pc*50/1,000,000 = (after some conversions) 7mm / day
  6. Apr 17, 2003 #5


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    Greetings !
    No, that is not what I'm asking. Space between
    particles and everything DOES expand. What I'm
    asking is how come this does not appear to affect
    them. Take a hydrogen atom that existed for billions
    of years - where's all the energy that the
    expansion of space is supposed to add to the
    electron in the orbital ? Is it emmited or maybe
    it's part of the reason and laws according to which
    these particles act(even if this part of the laws
    isn't known for now) ? Maybe atoms aren't even
    affected by the expansion becuase this energy
    (be it EM waves or expanding space) is not added
    when it is insufficient for orbital "jumps"
    (that would be really weird ).
    So, any expert info, please ?

    Live long and prosper.
  7. Apr 17, 2003 #6
    oh sorry i didnt mean u i meant tfast, thats ok i was just babling anyway:smile:
  8. Apr 17, 2003 #7
    Classical gravity has been shown to hold down to 1 mm by Cavendish experiments, but it may not hold on the atomic level. The critical gravitational acceleration for maintaining galaxies might be cH0=speed of light times Hubble constant (from "Matters of Gravity" on my site below).
    Last edited: Apr 17, 2003
  9. Apr 17, 2003 #8
    So you're saying that the solar system has expanded by roughly a factor of two since it formed (7mm * 365 * 4.65 billion ~ 12 billion km)? Actually, it would be more, given that Hubble's constant is closer to 70km/s/Mpc (although it's complicated by the fact that Hubble's constant actually changes with time). So, you're saying that when the universe was half its currrent size, the Milky Way was also half it's current size? What, and stars, too? Atoms? I can't possibly see how the expansion of the universe affects things on an atomic or molecular or solar system or even galactic scale. Not even by a tiny amount per year, because a tiny amount per year is a large amount per billions of years, and I don't think we have any astronomical evidence of that.
  10. Apr 17, 2003 #9
    Thanks very much for all the replies. Drag hit the nail on the head, but I think there may be a slight disconnect from my original question for some folks, however.

    As I originally stated, it's clear from our observations that gravity and other fundamental forces all keep matter in the same relative position, so we don't see things like the solar system expanding (at least not due to inflation; if we did, we would see ourselves, the distance between our own atomic nucleii, also expanding).

    However, if we accept that ALL space DOES expand, then it seems to me, and Drag summed this up very well, that there must be some energy expended to keep pieces of matter in relative position to one another as space expands between them. To me this implies that there is a measurable factor, and maybe, just possibly, even an observable effect from space "flowing" past objects.

    To illustrate my thinking, one analogy would be two rocks sitting in a shallow pool of water one meter apart. Each of the rocks is rooted to the ground securely. At the halfway point between the rocks, imagine a spring that bubbles water into the pool, from an entirely separate source (e.g. a mountain stream). Assuming no other perturbations of the pool, we would expect that water would flow outward from the spring and past the two rocks with some measurable velocity. This mass flow would exert a tiny but calculable force on the sides of the rocks facing the spring. In this thought experiment, the force would be countered by the reaction force from the rock's contact with the bottom of the pool, and this is where the analogy breaks down as a description of the phenomenon I'm supposing. In other words, the situation with inflation is different in that space itself expands, and there is no absolute reference frame such as the bottom of the pool in my analogy.

    Perhaps a better analogy would be to imagine another pair of rocks rooted securely in the ground, one meter apart, not in a pool this time, but connected to one another with an inflexible, indestructible rope. Imagine halfway between the two rocks, there is a fissure or fault through which magma bubbles to the surface, creating new ground between the rocks. Even as new ground is created between the rocks, they are kept at a steady one meter distance from one another via the rope. As the ground expands between them, the rocks will be dragged relative to the ground toward one another; the rope will exert a force opposite to the motion of ground away from the fissure. The ground will "flow" past the rocks. If the rope incorporated a force gauge along its length, we would be able to measure the force exerted by the ground on the rocks simply due to this flow of ground beneath them. If instead the rope were a spring, initially tensioned to try and bring the rocks closer together, the sum of the force on the rocks would be the initial tension plus the additional force due to the expansion of ground between them.

  11. Apr 18, 2003 #10


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    Greetings !
    O.K. maybe you're right cragwolf, but then - how
    does the expansion occur in terms of its effects
    on any matter and systems of bodies with rest mass ?
    I don't get it... [?] :frown:

    Live long and prosper.
  12. Apr 18, 2003 #11

    The Inflation of Space, and the Expansion of area/space are not the same thing. You are associating one product with another, and conversely asking,quite rightly, a Question of correspondance. The Atomic structure in question did not exist at the moment of inflation, Space as an area of energy(void of matter) that inflates expotentially, is offset by the later appearence of matter(that is not inflating).The analogy is that for matter oriented fields, matter 'inflation' occurs through radiative expansion and offsets/resists the inflation, ie matter interacts and photon pressure expands locally in Galaxies and gradually over time.

    Inflation is non-time dependant, for there was no matter and therfore no 4-dimensional spacetime.

    Now the space 'between' atoms and the space 'inside' atoms have cutoff area's, bounderies, so does the space between Galaxies.The space between Galaxies have the vaccum Energy, which can be seen as a follow-up to the moment of inflation, just as inflation occured pre-matter time, vaccum is the result expotentially after matter occured.

    Inflation evolution creates/evolved into Vaccum, its like the drag behind an aircraft as it passes from frame to frame in its forward motion.Because matter is compacted into Galaxies, the space between Galaxies is 2-dimensional, only energy that is 2-dimensional or plane/polarized oriented, travels into the area between Galaxies, and therefore the further one gets from a Galaxy, into area's that have no 3-dimensional structures, the vaccum increases. The space area around Galxies have 'less' vaccum, and more compactness, this is why Galaxies move through space vaccum.

    The area inside galaxies can be seen as 'expanding' into 3-dimensional space 'bubbles', everything that occurs inside Galaxies occur in Time, the Time of Galaxies does not extend across the space between Galaxies, therefore each Galaxy has an individual spacetime, unique and local. So the reason atoms do not 'Inflate' is because the atoms contained within a Galaxy, are isolated from the Space Vaccum Energy external to Galaxies, but if you could transport an Atom from within a Galaxy to another Galaxy, you would find that the farther you take the atom from a Galaxy, the more the Atom would 'Inflate/Expand'.

    Taking a single Atom into an area of extreme emptyness( expanding vaccum space)far ..far away from Galaxies, the you would see that Atom 'Explode'..it would be exposed to a enormous 'EXTRACTION FORCE', a Gravitational Repulsion extreme that would rip the Atom apart, a 'super-inflation'!
  13. Apr 18, 2003 #12


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    Thanks Ranyart ! :smile:

    P.S. Could you please also provide a link or two
    that explains this ? (Your message is somewhat
    complicated since it's relatively short.)
    Thanks !

    Live long and prosper.
  14. Apr 19, 2003 #13


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    Of course, it is entirely possible that the expansion of universe is the result of a natural force, in which case it would not be necessarily true the space is expanding at all. Just as the space between two magnets does not necessarily expand when they repel one another, the "fabric of space-time" is not necessarily expanding, just because galaxies are moving away from one another. It is possible that some repellent force, even weaker than gravity, but with even longer range, is responsible for the accelerating expansion of the cosmos.
  15. Apr 19, 2003 #14
    The way I understand it sounds at least similar to raynart's explanation. Only asymptotically flat spacetime expands. In other words, galaxies don't expand nearly as much as the space between galaxies because inside galaxies spacetime is curved, whereas in between them it is flat.
  16. Apr 20, 2003 #15
    "...the predominant cosmological theory is that space between them [galaxies] is expanding, thus causing them to fly apart..." {tfast}

    From time to time I've nearly convinced myself that there is no space between galaxies, planets, or atoms for that matter.

    Been over a decade but I recall opening a winter-stuck window in April only to see my effort dislodge a cloud of pollen trapped upon a spider's web between glass and screen. Natural light from the setting sun illuminated that orbiting pollen. Instantly, my hand, palm up, moved below this disruption. With every subtle movement of my hand the pollen contracted or expanded. I didn't touch the cloud. Certainly, we've all experienced these sorts of events with smoke, bubbles, etc. And I make no claim to originality here. Still I imagined, that day, all that is might just be in touch with everything else. No space between matter. Just position and relation. Perhaps even no motion as we currently understand motion.

    Any thoughts are welcome.

  17. Apr 20, 2003 #16


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    Greetings !
    So, this basicly implies a Universal expansion
    rest frame ? Just like (probably even the same) the
    CMBR rest frame ?
    (Now I can see more clearly what Ranyart meant above.)

    Live long and prosper.
  18. Apr 21, 2003 #17
    Hmm...I can't think of any reason why this would require a rest frame for the expansion of the universe.
  19. Apr 22, 2003 #18


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    Greetings !
    What is there to think ? You're saying that
    flat space-time expands more than curved space-time.
    How do you think you can call something flat/curved -
    you can only do that from a reference frame that is
    similar to that of CMBR - if curves match to galaxies
    and flat areas match what's in between.

    However, I believe the problem with the expansion
    in galaxies(some would still exist despite the
    above) - for rest-mass matter, is still not quite
    clear to me.

    Live long and prosper.
    Last edited: Apr 22, 2003
  20. Apr 22, 2003 #19
    I still prefer my simple, discrete lower limit to cosmological acceleration as an explanation to expansion only above the galactic scale.
  21. Feb 19, 2010 #20
    What if the small things are diffusing also? If (reasonably) everything was "expanding" nearly uniformly, would we notice?

    Else: What is things disorder relative to their Density?? The densest objects break down first, while things are still "slow", then as things accelerate, the smaller things entropy also?
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