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Thread: What is space?

  1. #1 What is space? 
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    Besides being what keeps everything from occupying the same place. Last time I debated this, one learned poster said that, and not in jest.


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    Space can seemingly expand from quantum size to present size of maybe a hundred billion light years in diameter and yet not change in any way.

    How can this be possible?

    If "spacetime" can be curved by large masses, then it is something more than an area measurable by what is contained within it.


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    I found this on another forum that the people who so casually talked of spacetime so much, when asked about it would not venture to say exactly what it was. I even googled it myself and there is virtually nothing on the subject, which is to my mind all important in cosmology.

    Rather than just being an area which expands, we are also told that spacetime is dragged around by the rotation of a planet, star or other large body. This sounds logical until you think, if it can be dragged around by gravity, then why does a black hole not start absorbing all the spacetime in it's immediate area like a sponge soaking up water and all the spacetime beyond that, etc? Like photons, it would be able to enter but unable to leave. If spacetime can expand indefinitely, then it can also contract indefinitely.
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  5. #4  
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    Quote Originally Posted by Cyberia
    Space can seemingly expand from quantum size to present size of maybe a hundred billion light years in diameter and yet not change in any way.How can this be possible?
    Of course it changed. It got bigger. What else would one expect space to do on expansion ?
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    Quote Originally Posted by Cyberia
    I found this on another forum that the people who so casually talked of spacetime so much, when asked about it would not venture to say exactly what it was. I even googled it myself and there is virtually nothing on the subject, which is to my mind all important in cosmology.

    Rather than just being an area which expands, we are also told that spacetime is dragged around by the rotation of a planet, star or other large body. This sounds logical until you think, if it can be dragged around by gravity, then why does a black hole not start absorbing all the spacetime in it's immediate area like a sponge soaking up water and all the spacetime beyond that, etc? Like photons, it would be able to enter but unable to leave. If spacetime can expand indefinitely, then it can also contract indefinitely.
    This "dragging" is called the Lens-Thirring effect. It is quite small. If I am not mistaken there experiments underway to detect it experimentally.

    You misunderstand the effect, black holes, and all of general relativity.

    Space can expand indefinitely simply because ther is no largest positive real number. It cannot contract indefinitely because the smallest non-negatoive real number is zero, as any fool should realize.

    There is a MOUNTAIN of information on this subject. Google "general relativity". Better yet, read a serious book on the subject -- like Gravitation by Misner, Thorne, and Wheeler or The large scale structure of space-time by Hawking and Ellis.
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by Cyberia
    Space can seemingly expand from quantum size to present size of maybe a hundred billion light years in diameter and yet not change in any way.How can this be possible?
    Of course it changed. It got bigger. What else would one expect space to do on expansion ?
    I pointed out that it got bigger. I thought you would have realised I was talking about space itself rather than it's size. Everything else in the universe, it if grows in area significantly, it changes in some way, becomes more diffuse, nebulous, loses energy, etc.
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    Quote Originally Posted by DrRocket
    This "dragging" is called the Lens-Thirring effect. It is quite small. If I am not mistaken there experiments underway to detect it experimentally.
    Yes it would be quite small for something like the Earth but how about supermassive black holes? Accretion disks show us that matter follows a circular route into a black hole rather than just falling in a straight line.

    You misunderstand the effect, black holes, and all of general relativity.

    Space can expand indefinitely simply because ther is no largest positive real number. It cannot contract indefinitely because the smallest non-negatoive real number is zero, as any fool should realize.
    A non answer. It does not explain how space can expand forever, but just says it can. As to contraction, it could presumably contract to a size where it no longer existed, though I did start with quantum size.

    There is a MOUNTAIN of information on this subject. Google "general relativity". Better yet, read a serious book on the subject -- like Gravitation by Misner, Thorne, and Wheeler or The large scale structure of space-time by Hawking and Ellis.
    The rubber mat with the balls on to represent the sun and the Earth going around it represents space well but can be nothing like reality. As someone said here the other day, gravity is bent spacetime, but how does it get bent? That's like saying that heat is hot air.

    It is said that gravity defines space but does it or does it just define the actions of what is in a gravity field? As I have already pointed out, if gravity can influence space, then sufficient gravity as in a black hole can drag in space forever.

    If we say space is literally nothing but is defined by what occupies it, then we have gravity which like say infra-red radiation which heats up whatever comes sufficiently close to it. As I have pointed out, it has been said that photons could have a very, very tiny but real mass which would explain their behaviour in a gravity field instead of relying on bending literally nothing. Acceleration behaves just like gravity but without any need to bend spacetime.

    I had a skim through the wiki article on GR and it so casually talks about curved spacetime. Yet it misses out what happens if spacetime can be bent, curved or anything else. If spacetime is a material as the article seems to say, then where is the explanation on how there can be endlessly more of it. Or if it literally expands, why it changes in no way (as in maybe the speed of light heading ever closer to infinite)?
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    Quote Originally Posted by Cyberia
    Yes it would be quite small for something like the Earth but how about supermassive black holes? Accretion disks show us that matter follows a circular route into a black hole rather than just falling in a straight line.
    That, [...], is the ordinary effect of gravity and mechanics. Thw same reason that the Earth ORBITS the sun. It is also the same reason for the circular flow near your bathtub drain. Ever hear of conservation of angular momentum ?

    Quote Originally Posted by Cyberia
    You misunderstand the effect, black holes, and all of general relativity.
    nope

    And we havwn't even gotten to GR. You misunderstand the second week of high school physics.


    Quote Originally Posted by Cyberia
    A non answer. It does not explain how space can expand forever, but just says it can. As to contraction, it could presumably contract to a size where it no longer existed, though I did start with quantum size.
    Not only can it expand forever, apparenyly it is doing just that. Google "lambda CDM model", and "cosmological constant".


    Quote Originally Posted by Cyberia
    The rubber mat with the balls on to represent the sun and the Earth going around it represents space well but can be nothing like reality. As someone said here the other day, gravity is bent spacetime, but how does it get bent? That's like saying that heat is hot air.
    The rubber mat is an ANALOGY for people who can't handle the mathematics of general relativity. Apparently you are not even capable of handling the analogy. No surprise there.

    Gravity is the effect of curved spacetime. The curvature is determined by the distribution of mass/energy as escribed by the Einstein field equations -- the stress-energy tensor which determines the curvature tensor. This is the very heart of general relativity.

    Quote Originally Posted by Cyberia
    It is said that gravity defines space but does it or does it just define the actions of what is in a gravity field? As I have already pointed out, if gravity can influence space, then sufficient gravity as in a black hole can drag in space forever.
    nope

    Not even wrong. Just word salad. More demonstration of profound ignorance.

    Quote Originally Posted by Cyberia
    If we say space is literally nothing but is defined by what occupies it, then we have gravity which like say infra-red radiation which heats up whatever comes sufficiently close to it. As I have pointed out, it has been said that photons could have a very, very tiny but real mass which would explain their behaviour in a gravity field instead of relying on bending literally nothing. Acceleration behaves just like gravity but without any need to bend spacetime.
    You have outdone even yourself. This is even worse than the preceeding paragraph.

    Quote Originally Posted by Cyberia
    I had a skim through the wiki article on GR and it so casually talks about curved spacetime. Yet it misses out what happens if spacetime can be bent, curved or anything else. If spacetime is a material as the article seems to say, then where is the explanation on how there can be endlessly more of it. Or if it literally expands, why it changes in no way (as in maybe the speed of light heading ever closer to infinite)?
    It just gets worse.

    Your understanding of basic physivcs is non-existent. My dog understands things betteer -- at least he is not walking around absolutely convinced of stuff that is completely wrong. Your knowledge of physics is actually negative.
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    Quote Originally Posted by DrRocket
    That, [...], is the ordinary effect of gravity and mechanics. Thw same reason that the Earth ORBITS the sun. It is also the same reason for the circular flow near your bathtub drain. Ever hear of conservation of angular momentum ?
    Ever hear of water orbiting a plug hole for 4.6 billion years?

    And we havwn't even gotten to GR. You misunderstand the second week of high school physics.
    You did that much? You surprise me.

    Not only can it expand forever, apparenyly it is doing just that. Google "lambda CDM model", and "cosmological constant".
    But how can something that has form in that it can expand, contract, be warped expand forever?


    The rubber mat is an ANALOGY for people who can't handle the mathematics of general relativity. Apparently you are not even capable of handling the analogy. No surprise there.

    Gravity is the effect of curved spacetime. The curvature is determined by the distribution of mass/energy as escribed by the Einstein field equations -- the stress-energy tensor which determines the curvature tensor. This is the very heart of general relativity.
    So how about we have spaceheat then? If instead of gravity doing what it should do, it instead must do so by affecting space to accomplish anything, why not have spaceheat too? If a magnet pulls a bar of iron, we do not say that it warps the space between the iron and the magnet to do so.

    Not even wrong. Just word salad. More demonstration of profound ignorance.
    I have noticed that "word salad" followed by an insult is your way of not answering a question that you find too difficult.

    You have outdone even yourself. This is even worse than the preceeding paragraph.
    Another non answer.

    Your understanding of basic physivcs is non-existent. My dog understands things betteer -- at least he is not walking around absolutely convinced of stuff that is completely wrong. Your knowledge of physics is actually negative.
    And another.

    Even your talking dog could say someone was wrong with just as much meaning as you do. It is just a mindless statement which is not backed up by any evidence, so worthless.
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  11. #10  
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    As I understand it, space is simply the presence of dimensions, of a "place", as opposed to complete non-existence or "non-place" such as the seventh side of a standard die. In that sense, space is exactly simply the thing stuff exist in. That is why there can be no such thing as an "outside" to the universe in the big bang creation model.

    Ever hear of water orbiting a plug hole for 4.6 billion years?
    A uniform ball orbiting a uniform larger ball where they are the only things that exist, will orbit forever.

    I am also interested in understanding why space expands. For instance, why is energy required if expansion occurs uniformly with or without the presence of matter? Is there an energy value coupled to any volume of space?
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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    Quote Originally Posted by KALSTER
    I am also interested in understanding why space expands. For instance, why is energy required if expansion occurs uniformly with or without the presence of matter? Is there an energy value coupled to any volume of space?
    That is one of the biggest unsolved problems in physics.

    From observation space s expanding and has been since the big bang. that could be due to the initial conditions of the big bang. Nobody knows what those conditions might have been.

    It could be due to the effect of the "inflation field" if it exists. Inflation seems to explain a lot of what is observed. But it requires the existence of a somewhat mysterious field, and nobody knows what it might be.

    And now, due to observations since about 1998 it appears that the expansion rate is accelerating. Nobody knows why. It has been given a name, dark energy. The effect is identical to a positive cosmological constant in general relativity. Nobody knows why there should be the observed positive constant.

    The vacuum energy of quantum electrodynamics results in a negative pressure term that when included in the stress-energy tensor acts as a positive cosmological constant. Unfortunately the term exceeds what is actually observed by 120 ORDERS OF MAGNITUDE. That is a ludicrous error. Nobody knows why.

    So, if you figure out why space is expanding the way that it seems to be, a Nobel Prize (at the very least) awaits.
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    Cool. I think I'll move over to the New Hypothesis section now.
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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    Quote Originally Posted by KALSTER
    As I understand it, space is simply the presence of dimensions, of a "place", as opposed to complete non-existence or "non-place" such as the seventh side of a standard die. In that sense, space is exactly simply the thing stuff exist in. That is why there can be no such thing as an "outside" to the universe in the big bang creation model.
    If the universe is an expanding hypersphere, no. But if it is just in 3 physical dimensions then photons will far outpace matter and so leave the "material universe" far, far behind.

    I am also interested in understanding why space expands. For instance, why is energy required if expansion occurs uniformly with or without the presence of matter? Is there an energy value coupled to any volume of space?
    There has been some crazy values assigned to the energy of space which would light the universe up like a supernova. But it seems that space is always exactly the same, no matter how much area it occupies.
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    Quote Originally Posted by Cyberia
    Quote Originally Posted by KALSTER
    As I understand it, space is simply the presence of dimensions, of a "place", as opposed to complete non-existence or "non-place" such as the seventh side of a standard die. In that sense, space is exactly simply the thing stuff exist in. That is why there can be no such thing as an "outside" to the universe in the big bang creation model.
    If the universe is an expanding hypersphere, no. But if it is just in 3 physical dimensions then photons will far outpace matter and so leave the "material universe" far, far behind.
    AKA the Cosmic Microwave Background
    Quote Originally Posted by Cyberia
    I am also interested in understanding why space expands. For instance, why is energy required if expansion occurs uniformly with or without the presence of matter? Is there an energy value coupled to any volume of space?
    There has been some crazy values assigned to the energy of space which would light the universe up like a supernova. But it seems that space is always exactly the same, no matter how much area it occupies.
    And this is based on what evidence? Please elaborate.
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    [quote="Dishmaster"]AKA the Cosmic Microwave Background

    In an open universe you have matter expanding at mutliples of 14 mps per million light years but light moving at 186,282 mps so leaving the universe far behind, the universe would be continually losing energy. In a closed system, Eddington, eighty odd years ago worked out that starlight (and heat) would produce a temperature of about 3K.

    And this is based on what evidence? Please elaborate.
    98% of the energy of a proton seems to come from the empty space inside it (as in not the quarks). If this were literally the energy of "nothing" instead of more likely unseen particles, the same energy applied to all of "empty space" had I think 121 noughts to it so rather energetic.
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    Quote Originally Posted by Cyberia
    In an open universe you have matter expanding at mutliples of 14 mps per million light years but light moving at 186,282 mps so leaving the universe far behind, the universe would be continually losing energy. In a closed system, Eddington, eighty odd years ago worked out that starlight (and heat) would produce a temperature of about 3K.
    This is just factually wrong. You are not allowed to make up your own facts.

    Matter is not expanding.

    Temperatures of the universe are not a function of whether it is open or closed, and no one knows if it is open or closed.



    Quote Originally Posted by Cyberia
    And this is based on what evidence? Please elaborate.
    98% of the energy of a proton seems to come from the empty space inside it (as in not the quarks). If this were literally the energy of "nothing" instead of more likely unseen particles, the same energy applied to all of "empty space" had I think 121 noughts to it so rather energetic.
    The mass/energy of the proton is in large part due to the strong interaction that binds the quarks , a prediction of quantum chromodynamics. The estimate of the vacuum energy of space from quantum electrodynamics does indeed result in an estimate for the cosmological constant that is high by about 120 orders of magnitude, but no one understands why -- this is a major open problem in quantum field theory.

    So as usual you have mis-understood, mis-stated and generally garbled the truth.
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    Quote Originally Posted by DrRocket
    This is just factually wrong. You are not allowed to make up your own facts.
    Evidece?

    Matter is not expanding.
    Other than where local gravity stops it, matter is said to be moving apart in the universe. The term is expansion, as in expanding.

    Temperatures of the universe are not a function of whether it is open or closed, and no one knows if it is open or closed.
    If radiation can escape the expanding universe, it is losing energy. If it cannot the universe will slowly heat up.


    Quote Originally Posted by Cyberia
    And this is based on what evidence? Please elaborate.
    98% of the energy of a proton seems to come from the empty space inside it (as in not the quarks). If this were literally the energy of "nothing" instead of more likely unseen particles, the same energy applied to all of "empty space" had I think 121 noughts to it so rather energetic.[/quote]

    The mass/energy of the proton is in large part due to the strong interaction that binds the quarks , a prediction of quantum chromodynamics. The estimate of the vacuum energy of space from quantum electrodynamics does indeed result in an estimate for the cosmological constant that is high by about 120 orders of magnitude, but no one understands why -- this is a major open problem in quantum field theory.

    So as usual you have mis-understood, mis-stated and generally garbled the truth.[/quote]

    We have quarks producing 49 times times their own energy by strong interactions? You'll believe anything.

    OK, it's been years since I heard the lecture so I misremembered 120 orders of magnitude as 120 noughts.

    Where did you get your quote from?
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    Quote Originally Posted by Cyberia
    radiation can escape the expanding universe, it is losing energy. If it cannot the universe will slowly heat up.
    Rubbish

    This would violate both the first and second laws of thermodynamics.

    Your abject ignorance of basic physics is showing.

    The rest of your assertions are also factually wrong and even dumber.
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by Cyberia
    radiation can escape the expanding universe, it is losing energy. If it cannot the universe will slowly heat up.[
    Rubbish

    This would violate both the first and second laws of thermodynamics.

    Your abject ignorance of basic physics is showing.

    The rest of your assertions are also factually wrong and even dumber.

    I don't have to prove how dumb you are. I could never do such a good job of it as you do. You even boast about it.

    Energy is tied up in atoms. We have stars which work by nuclear fusion and liberate a lot of this energy. All this freed energy in a closed universe would make it ever hotter. In an open universe where energy can escape, all forms of energy could escape as they would naturally leave matter far behind.

    I can't make it any easier than that.
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    Quote Originally Posted by Cyberia

    I don't have to prove how dumb you are. I could never do such a good job of it as you do. You even boast about it.

    Energy is tied up in atoms. We have stars which work by nuclear fusion and liberate a lot of this energy. All this freed energy in a closed universe would make it ever hotter. In an open universe where energy can escape, all forms of energy could escape as they would naturally leave matter far behind.

    I can't make it any easier than that.
    [...]

    Energy cannot escape the universe -- because it is the UNIVERSE.

    The difference between an open universe and a closed universe is the topology of space-like slices of spacetime. If they are compact the universe is called closed, and if not the universe is called open. That is the meaning of the terms in cosmology, which is different from the meaning of open and closed as applied to thermodynamic systems. By definition the universe is thermodynamically closed. If it were not, it would not be the universe.

    There is no net increase in energy in a thermodynamically closed system, and heat and temperature are different. The overall temperature of the universe is decreasing due to expansion -- whether the universe is open or closed.

    You clearly failed freshman physics, if indeed you were ever enrolled.
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    Energy cannot escape the universe -- because it is the UNIVERSE.
    You make the mistake of thinking the universe is everything inside a bubble and nothing can escape. We have no evidence for this, as in proof of a fourth physical dimension.

    The difference between an open universe and a closed universe is the topology of space-like slices of spacetime. If they are compact the universe is called closed, and if not the universe is called open. That is the meaning of the terms in cosmology, which is different from the meaning of open and closed as applied to thermodynamic systems. By definition the universe is thermodynamically closed. If it were not, it would not be the universe.
    The universe will expand forever. All the way back through history it was a lot smaller than it was now, so the area over which the gravity of the entire mass of the universe had to act was much smaller. It not only continued expanding but increased speed of expansion. Who needs dark energy when it would naturally do so as gravitational sources become further apart and because of the very limited speed of gravity which means it takes ever longer to reach ever further objects. So open and closed in that sense is meaningless.

    Since the universe is not a black hole, energy can and will escape from it since light far outdistances all matter.

    There is no net increase in energy in a thermodynamically closed system, and heat and temperature are different. The overall temperature of the universe is decreasing due to expansion -- whether the universe is open or closed.
    You could safely hold a lump of rock in your hand which if all the atom energy were released from it, would power America's energy needs for a few weeks. While stars are not as efficient, they are fusing hydrogen and helium, etc (which left alone would have been at 2.7K) into heavier elements and releasing huge amounts of heat and other energy as they do so. In a closed system, that energy would warm up the entire universe (I think there are some 3x10^24 stars at latest estimate).

    You clearly failed freshman physics, if indeed you were ever enrolled.
    Parroting accepted science merely means a good memory. Not any ability to do anything with such knowledge.
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    We have no evidence for this, as in proof of a fourth physical dimension.
    You just keep saying this, despite numerous corrections. GR and the big bang does not need a 4th physical dimension. The balloon analogy is simply that; an analogy. We are still dealing with only three space-like dimensions.

    The universe will expand forever. All the way back through history it was a lot smaller than it was now, so the area over which the gravity of the entire mass of the universe had to act was much smaller. It not only continued expanding but increased speed of expansion. Who needs dark energy when it would naturally do so as gravitational sources become further apart and because of the very limited speed of gravity which means it takes ever longer to reach ever further objects. So open and closed in that sense is meaningless.
    You have it wrong. Think of how escape velocity works. With a constant motion, gravity will tend to slow down movement. Depending on the speed of expansion, you can have the recession speed exactly equalling "escape velocity" with expansion slowing forever, but never quite stopping. Or you can have expansion slowing, stopping and then contraction starts, or you can have expansion outstripping the pull of gravity. That is with constant expansion. Current WMAP data suggests that expansion is accelerating though, which requires energy nobody knows the origin of, hence "dark energy".

    Since the universe is not a black hole, energy can and will escape from it since light far outdistances all matter.
    Into what? Where can it escape to if the universe is all there is?
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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  24. #23  
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    Quote Originally Posted by Cyberia
    Energy cannot escape the universe -- because it is the UNIVERSE.
    You make the mistake of thinking the universe is everything inside a bubble and nothing can escape. We have no evidence for this, as in proof of a fourth physical dimension.

    The difference between an open universe and a closed universe is the topology of space-like slices of spacetime. If they are compact the universe is called closed, and if not the universe is called open. That is the meaning of the terms in cosmology, which is different from the meaning of open and closed as applied to thermodynamic systems. By definition the universe is thermodynamically closed. If it were not, it would not be the universe.
    The universe will expand forever. All the way back through history it was a lot smaller than it was now, so the area over which the gravity of the entire mass of the universe had to act was much smaller. It not only continued expanding but increased speed of expansion. Who needs dark energy when it would naturally do so as gravitational sources become further apart and because of the very limited speed of gravity which means it takes ever longer to reach ever further objects. So open and closed in that sense is meaningless.

    Since the universe is not a black hole, energy can and will escape from it since light far outdistances all matter.

    There is no net increase in energy in a thermodynamically closed system, and heat and temperature are different. The overall temperature of the universe is decreasing due to expansion -- whether the universe is open or closed.
    You could safely hold a lump of rock in your hand which if all the atom energy were released from it, would power America's energy needs for a few weeks. While stars are not as efficient, they are fusing hydrogen and helium, etc (which left alone would have been at 2.7K) into heavier elements and releasing huge amounts of heat and other energy as they do so. In a closed system, that energy would warm up the entire universe (I think there are some 3x10^24 stars at latest estimate).

    You clearly failed freshman physics, if indeed you were ever enrolled.
    Parroting accepted science merely means a good memory. Not any ability to do anything with such knowledge.

    All wrong -- see Kalister's post.

    Come on. You're putting us on, right ? Can anybody really be that stupid ?
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