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Thread: Expansion of Space vs. Expansion of Mass

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  1. #1
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    Expansion of Space vs. Expansion of Mass

    I'm just discovering the podcast, and just listened to episode 5, titled "The Expansion of the Universe and the Microwave Cosmic Background".

    At one point, it was mentioned that while space is expanding, our "heads are not"....So, the implication being that the space between objects is expanding, but objects themselves are not expanding. Did I understand that correctly?

    To use the raisin bread analogy, when the bread expands, increasing the distance between the raisins, are the raisins themselves not expanding in size?

    If massive objects are not expanding, then what happens to the "inner space" that exists within all matter, i.e. most solid matter is empty space, and if this is not expanding how is it different from the space between galaxies, etc.?

    On the other hand, if objects are expanding in dimension right along with space, then the relative dimensions of the universe would not be changing. By that I mean, if we say that the size of the orbit of the earth around the sun is 1 astronomical unit, then the value of 1 AU is expanding right along with the universe, but to our perspective, it is remaining constant, relative to the distance between familiar objects, such as the distance between new york and los angeles....But I gather the evidence is contra to the idea that physical dimensions of massive objects are expanding....

    One thing that was interesting to me, was that the cosmic background radiation is slowly shifting to longer wavelengths (e.g. lower energy). Does this mean that all transmitted electromagnetic photons lose energy overtime? Is it something we could measure? Could we detect a loss of energy of a lightsource between point A and point B? (I'm guessing it would be a rather difficult experiment, indeed)....

    Jason
    Last edited by jbrosenberg; 2007-Jun-02 at 09:05 PM. Reason: fixed typo

  2. #2
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    I would assume that expansion of space would include that between atoms as well. So yes objects are expanding.

    Expansion is small - only when you measure to huge distances does it make itself appearent.

  3. #3
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    Imagine it this way...

    You might be 5 foot 7 and everything in your world is reletively normal.

    If you grew to 300 feet everything would seem smaller. But if everything grew as you did, and at the same rate, you would never notice the difference.

    But the difference between 5 foot 7 and 300 feet is infintessimal compared to astrological distances.... which is (as said above) when they become apparent.

  4. #4
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    Wink no

    no the raisens are not expanding just space atoms remain unchanged
    space expands......atoms sit in space but do not strech with it....


  5. #5
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    Are objects in expanding space themselves expanding?

    www.universeadventure.org:

    "Planets, stars, and galaxies are bound together by gravity. On the short distance scales present in these systems the force of gravity is great enough to resist and stop the expansion of space. Gravity opposes the expansion of the universe on larger scales as well, but since the strength of gravity falls with the square of the distance, the force is not enough to halt the expansion. If every object expanded with space, including ourselves, we would not perceive any expansion at all."

    And at even smaller scales the strong nuclear force and the electromagnetic force overcome the expansion of space between particles.

    www.particleadventure.org:

    "What holds it together? The universe, which we know and love, exists because the fundamental particles interact. These interactions include attractive and repulsive forces, decay, and annihilation.
    There are four fundamental interactions between particles, and all forces in the world can be attributed to these four interactions!
    Gravity; Electromagnetic; Strong; Weak.
    That's right: Any force you can think of -- friction, magnetism, gravity, nuclear decay, and so on -- is caused by one of these four fundamental interactions."

    "The electromagnetic force causes like-charged things to repel and oppositely-charged things to attract. Many everyday forces, such as friction, and even magnetism, are caused by the electromagnetic, or E-M force. For instance, the force that keeps you from falling through the floor is the electromagnetic force which causes the atoms making up the matter in your feet and the floor to resist being displaced."

    "Atoms usually have the same numbers of protons and electrons. They are electrically neutral, therefore, because the positive protons cancel out the negative electrons. Since they are neutral, what causes them to stick together to form stable molecules?
    The answer is a bit strange: we've discovered that the charged parts of one atom can interact with the charged parts of another atom. This allows different atoms to bind together, an effect called the residual electromagnetic force.
    So the electromagnetic force is what allows atoms to bond and form molecules, allowing the world to stay together and create the matter you interact with all of the time."

    "Quarks have electromagnetic charge, and they also have an altogether different kind of charge called color charge. The force between color-charged particles is very strong, so this force is "creatively" called The Strong Force.
    The strong force holds quarks together to form hadrons. And while quarks have color charge, composite particles made out of quarks have no net color charge (they are color neutral). For this reason, the strong force only takes place on the really small level of quark interactions, which is why you are not aware of the strong force in your everyday life."

    "So now we know that the strong force binds quarks together because quarks have color charge. But that still does not explain what holds the nucleus together, since positive protons repel each other with electromagnetic force, and protons and neutrons are color-neutral.
    So what holds the nucleus together? Huh?
    The answer is that, in short, they don't call it the strong force for nothing. The strong force between the quarks in one proton and the quarks in another proton is strong enough to overwhelm the repulsive electromagnetic force.
    This is called the residual strong interaction, and it is what "glues" the nucleus together."




    Hope this helps?

  6. #6
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    As I understand it, our heads don’t expand, the distance between earth and the sun doesn’t expand, and our galaxy as a whole doesn’t either. That’s because these objects are gravitationally bound. Gravity between these objects is stronger than the force that is driving the expansion of the universe. So it’s the space between astronomically far apart bodies that is expanding, because gravity between these bodies is weakened by the distance to the degree that allows to the expansion force to win over gravity.

    Re the other question, yes, red shift can be measured between two points, but they have to be moving in relative to each other. I think that one of the tests that scientists use to determine the speed of space ships is through the red shift effect in the radio waves that is broadcasted back to earth from space ships.

  7. #7
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    Quote Originally Posted by jbrosenberg View Post
    If massive objects are not expanding, then what happens to the "inner space" that exists within all matter, i.e. most solid matter is empty space, and if this is not expanding how is it different from the space between galaxies, etc.?
    The expansion is an effect related to gravity. On the largest scales, electromagnetism and other forces don't play much of a role, so gravity is king. On smaller scales, gravity or electromagnetism or other forces work to keep collections of particles together. So on the large scales, there can be an expansion that is not related to behaviour that we see more locally.
    One thing that was interesting to me, was that the cosmic background radiation is slowly shifting to longer wavelengths (e.g. lower energy). Does this mean that all transmitted electromagnetic photons lose energy overtime? Is it something we could measure? Could we detect a loss of energy of a lightsource between point A and point B? (I'm guessing it would be a rather difficult experiment, indeed)....
    This loss of photon energy over transmission time is something that is used in cosmological measurements. Over great distances, it's impressive. Over small distances, it's not so big.

  8. #8
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    Is there any sort of force/particle interaction between expanding space and gravitationally bound matter? I'm thinking of something akin to friction. As space "grows" around us is there a measurable phenomena besides increased acceleration and distances between distant objects?

  9. #9
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    Quote Originally Posted by cepheidstar View Post
    Is there any sort of force/particle interaction between expanding space and gravitationally bound matter? I'm thinking of something akin to friction. As space "grows" around us is there a measurable phenomena besides increased acceleration and distances between distant objects?
    Maybe try looking into "Higgs Fields" and "Higgs Bosons."

    My (very limited!) understanding is that the Higgs Field is a scalar field pervading all of space--it's interaction with particles via the Higgs Boson gives rise to Mass and is something like the "friction" you are thinking of. I believe they are hoping to observe the Higgs Boson when the latest generation of particle accelerators come online. Might be worth a google?
    Last edited by Steve Limpus; 2007-Jul-20 at 01:15 AM. Reason: typo

  10. #10
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    jbrosenburg,

    This "difference" in which you're talking about is what I define as gravity in my thread http://www.bautforum.com/against-mai...-universe.html. The fifth paragraph explains this battle of expansion. I wish this thread was in ATM, so I could comment further about the subject at hand. Best of luck figuring it out in the mainstream!

  11. #11
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    the effects of the expansion are basically nullified near a gravity source.

    Quote Originally Posted by jbrosenberg View Post
    I'm just discovering the podcast, and just listened to episode 5, titled "The Expansion of the Universe and the Microwave Cosmic Background".

    At one point, it was mentioned that while space is expanding, our "heads are not"....So, the implication being that the space between objects is expanding, but objects themselves are not expanding. Did I understand that correctly?

    To use the raisin bread analogy, when the bread expands, increasing the distance between the raisins, are the raisins themselves not expanding in size?

    If massive objects are not expanding, then what happens to the "inner space" that exists within all matter, i.e. most solid matter is empty space, and if this is not expanding how is it different from the space between galaxies, etc.?

    On the other hand, if objects are expanding in dimension right along with space, then the relative dimensions of the universe would not be changing. By that I mean, if we say that the size of the orbit of the earth around the sun is 1 astronomical unit, then the value of 1 AU is expanding right along with the universe, but to our perspective, it is remaining constant, relative to the distance between familiar objects, such as the distance between new york and los angeles....But I gather the evidence is contra to the idea that physical dimensions of massive objects are expanding....

    One thing that was interesting to me, was that the cosmic background radiation is slowly shifting to longer wavelengths (e.g. lower energy). Does this mean that all transmitted electromagnetic photons lose energy overtime? Is it something we could measure? Could we detect a loss of energy of a lightsource between point A and point B? (I'm guessing it would be a rather difficult experiment, indeed)....

    Jason

  12. #12
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    Also do microscopic dimensions expand with the expansion of space?

  13. #13
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    I hope those who have expressed contrary ideas in this thread will consider the follow points:

    The constituents of matter are held together by forces: Protons and neutrons are made up of quarks held together by gluons that exert extremely strong forces that actually become even stronger as the distances between the particles increase. Atomic nuclei, made up of protons and neutrons, are held together by the nuclear "strong force". Atoms, made up or atomic nuclei and "orbiting" electrons, are held together by electrical forces. Molecules, made up of atoms, are held together by valence forces. Bulk matter, made up of molecules, is held together by several kinds of intermolecular forces. These forces, all short range, meaning that they fall off rapidly with distance, are all many orders of magnitude stronger than that of gravitation.

    Space is simply the medium in which matter resides. Matter moves relative to space only when acted upon by forces associated with energy. Space is expanding under the inertial impetus imparted to it at the beginning of the Big Bang. Objects - nuclear particles, atoms, molecules, and solid matter -- are imbedded in space and are carried along by space when it expands..

    The negative energy that seems to be forcing space to expand is expected to increase in effectiveness over time over shorter and shorter distances, eventually overcoming the gravitational forces that hold galaxy clusters together, then galaxies themselves, then star clusters, then planetary systems, then planets, then solid matter, then molecules, then atoms, and, eventually, nuclei, protons and neutrons. Finally, even protons and neutrons are expected to dissociate into quarks, and the Universe will, for all practical purposes, have come to an end.
    Last edited by dcl; 2008-May-17 at 08:00 PM.

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    For the big-rip scenario to be expected, wouldn't the expansion of space have to have an accelerating rate even between two points of the same distance such as 70k/sec/mega parsec/year (or any other time frame, maybe 13.7 billion years)?

    With the observed expansion rate of 70k/sec/mega parsec, the space between two objects, ie. the Sun and Earth is expanding, but due to gravity they are moving towards each other at a faster rate than that expansion, so the system's over size then only remains constant because the lateral inertia has us in orbit. I imagine that if the Earth left a trail on medium of space as it orbited the Sun, we'd see a spiral moving outward from the system as space expanded.

    If space wasn't expanding, I bet the Earth would need to be moving a wee bit faster laterally to maintain this size of an orbit. That math is beyond this mere kindergarten teacher in Thailand, I'm afraid.

    I don't see gravity as affecting the expansion of space at all, only the curvature of the space, hence the motion of objects through the medium of space and their gravitational interaction with each other. The expansion of space should therefore not transmit any inertia to the objects that are seemingly accelerating apart from each other within the medium, which is why objects can be moving faster than the speed of light relative to one another, but not in relation to the medium of space.

    Which type of rate has been observed? I've only heard the current rate of 70k/sec/MP on astronomycast. Is that rate expected to be increasing ie.. perhaps 70k/sec/MP/13.7 billion years? If so, hello, big-rip! I imagine it shouldn't be too long till our observations can rule one out if they haven't already.

    edit: previously had expansion rates at 20k per... must have misheard the podcast, or just getting old. thanks speedfreek for the correction
    Last edited by Aaron; 2008-May-17 at 05:20 PM.

  15. #15
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    The rate is actually around 70 km/s per Megaparsec. For every megaparsec in distance (3,262,000 light years), the rate of expansion increases by 70 km/s, it is as simple as that (although in truth it is not so simple as that is an average over the age of the universe! The rate has been decreasing and then increasing over time, but that is the average over that time).

    See Hubbles Law for more info.

  16. #16
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    The Big Rip would not require an accelerating expansion rate. It would require only that the expansion continue until distances between galaxies had become so great that gravitation (curvature of space() no longer affected their relative motion (geodesics). There is no need to bring numerical values into the discussion.

    Although space between nearby objects such as the sun and earth is expanding, the earth's orbit is presumably remaining its present size because gravitation (local space curvature caused by presence of the sun) holds earth at its present distance. Eventually, as expansion of space becomes effective over distances of the order of distances between objects in the solar system, planetary orbits will begin to expand, resulting in eventual dissolution of the solar system. When local space curvature becomes appreciable over distances of the order of atomic dimensions, then atoms will fall apart as electrons drift away from their nuclei.

    Enjoy the present Universe while you can!

  17. #17
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    Maybe I'm just conceptually misunderstanding this, but it seems that with any two objects "locked" by an attractive force(where that attractive force is in effect causing the two objects to accelerate toward each other faster than the rate of the space-medium's expansion), even as space expands between them, they would be accelerating through that expanding medium toward each other maintaining the same distance.

    Converting the expansion rate to say AU's, 0.00000000034k/sec/AU (somebody probly needs to check the conversion there though it really doesn't matter for the discussion)
    If observing a constant distance, say 1AU in Earth's orbit, the expansion rate between the Earth and Sun is always 0.00000000034k/sec meaning that as Earth orbits, it gradually spins toward the sun at that rate in its orbit to compensate for the expansion of space thus maintaining a constant distance. The expansion rate we're dealing with is now .00000000034k/sec and not accelerating in relation to the constant distance. Just as 70k/sec/MP expansion is constant and not accelerating if always observing the distance of 1 Megaparsec.

    For expansion rates to accelerate when observing a constant distance (objects in orbit as well as nuclear bonds), it seems there would need to be another time element in the expansion rate... Can someone help with an analogy if this is not the case? I'm trying to get my mind around it so I can come up with a way to present it to my older students.

  18. #18
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    Your counterargument started off with "with any two objects 'locked' by an attractive force where the attractive force is in effect forcing the two objects to accelerate toward each other faster than the rate of the space medium's expansion, even as space expands between them, they would be accelerating through that expanding medium toward each other maintaining the same distance".

    The situation you describe is not what usually prevails. Gravity does not usually cause distances of objects to decrease. Instead, because objects are rarely moving directly toward each other, it holds them in orbits. As negative energy acts on the space inside orbits, the latter tend to expand until the gravitational force is no longer sufficient to hold them in orbit, resulting in the orbits expanding. But, except for the largest orbits, expansion because of negative energy is currently negligible except for orbits of cosmological size and is expected to remain so for millions if not billions of years to come. Only when negative energy density becomes much larger than it is now will dimensions of smaller orbits be affected.

    I would urge you to avoid bringing specific numerical values into a discussion when, as in the present discussion, they are not essential to the argument. Thus, the earth's distance from the sun, an erroneously supposed rate of increase in the earth's orbital radius derived from the Hubble constant, and the Hubble constant itself have no bearing on the argument.

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