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Space: Is it a place? Or is it a physical entity?

  1. May 24, 2003 #1
    [SOLVED] Space: Is it a place? Or is it a physical entity?

    Space is nothing more than an empty room. From reading some threads I get the impression that some people believe that space, or spacetime, is a physical construct that can have effect on the motion of bodies. But the reality is that space is just a place in which physical things reside. In the area that is space there are countless objects, by our limited calculability, but each and every one of them has their place in space the same way that a chair takes up space in an empty room. This placement is true for stars, or galaxies, or any of the fields that such matter produces.

    From our perspective, the universe seems unlimited. No matter the strength of our newest telescopes, we have found no perimeter to the material placement of the objects in space. But there must be a peripheral area, an outer boundary, where the physical objects in space border the empty space beyond. In that empty space beyond there will be no gravity or any other type of field because there will be no physical matter to generate any kind of field. This determines that the universe we live in is a finite, organized construct, no different than a galaxy except for size and the arrangement of the mass within it.
  2. jcsd
  3. May 24, 2003 #2
    Some people cannot handle that:

    1. Not all things are alive.

    2. Not all living things experience events the same as them.

    It's a serious humanitarian issue. We're trying to clear it up, please give us perhaps 500 to 1000 years, and we will return your request.

    --Management of Life
  4. May 24, 2003 #3


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    Thanks for clearing all that up John... [zz)]

    - Warren
  5. May 25, 2003 #4
    You're welcome, because it certainly needed clearing up. When people begin talking about the "curvature" of space, it is evident that their concept of reality is tinged by popular culture. To assign physical properties to an area is to ignore the physical properties of the phenomena which occupy that area. Take a gravity field as the start of an example. Since a gravity field is the cumulative gravities of all the particles of mass which comprise a body, then the larger the body is determines the greater the strength of the gravity. The distance the gravity field is projected from the body is determined by the cumulative amount of gravity having to reside around the body of mass while it attracts inward toward the center.

    A different field which can reside in the same area as a gravity field is a light field. If our body of example is a star, then ,as well as having a gravity field, it projects a photon field in every outward direction and those photons travel until they collide with some physical object, such as a planet, or until they exhaust their stored energy and become a dormant particle. That burned out, dormant state of photons is most likely what is being detected as the background disturbance in space which so many scientists have trouble categorizing.

    The fact that gravity fields can interact and coexist in a given area is exampled by a galaxy, which is a cohesive unit. The cohesive units comprise ever larger constructs, such as clusters of galaxies, and then clusters of clusters of galaxies, and so on and on until all the material in the universal unit is accounted for. When you start trying to assign imaginary characteristics, such as curvature of spacetime, to the physical attributes of that reality, then you are ignoring physics and engaging in fanciful daydreaming which is fun to do sometimes, but it is not science.

    A lot of the space theories presented grow so weird when they are conceptualized that the proponents of them say that physics breaks down when certain points are reached. That has got to be the most infantile way of engaging in physics that is imaginable. Physics is never going to break down or quit working so that someone can have a billion suns scrunch down to an imaginary singularity. The same can be said for string theory, or superstring theory or any other kind of theory which imagines dimensions that physics cannot describe. If you want to think of science for real, then you have to disregard those fad theories and think of logical progression. When you think of, and discuss, cartoon theories which have zero possibility of being correct, then you do your mind no good with that kind of nonsensical exercise. If that is your only way of discussing science, then you'd be better off utilizing your time by whitewashing your fence.
  6. May 25, 2003 #5


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    Yes, they are called cosmologists. Those crazy folks say the space-time metric is equivalant to the gravitational field itself. Wacky, eh? One crazy physicist (Einstein) even went as far as to say if you could somehow throw a switch to turn off the gravitational field, space-time would disappear! It's funny how an education in physics and cosmology can bring these people so out of touch with reality.

    Good work, you've discovered what the ancient greeks knew 5000 years ago. They knew the true reality of space, and weren't burdened by the findings of modern science like cosmologists today are. Damn gravity, quantum mechanics, field theories, and relativity. But so long as you stay away from an education, you shouldn't lose your common sense about the obvious reality of space.

    Good thinking. Just be sure not get an education in physics (or logic) or you could be in trouble like the rest of those scientists. Don't let those crazy physicists set you on the wrong path!
  7. May 25, 2003 #6
    Hmmmm......a rather childish response, eh?

    Quote:..."One crazy physicist (Einstein) even went as far as to say if you could somehow throw a switch to turn off the gravitational field, space-time would disappear!"

    Perhaps you should reference that statement so it can be read in full context. Not that I doubt the veracity of it, of course, because it does make sense. If space-time disappears when gravity is turned off, then it can only be a mental description used for thought experiments and can in no way have a real existence of it's own. If space-time had any real properties, then some form of them would linger as residual effects after the gravity was turned off. Einstein clearly knew his business.
  8. May 25, 2003 #7


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    i like the occams razor way.
  9. May 25, 2003 #8


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    Silly posts encourage childish responses. The obvious reality of space you mention is somehow missed by physicists around the world. Take a closer look, and you'll see that there is a reason for this.

    Anyway, the Einstein quote is from a book. I believe it was "The Meaning of Relativity". If the gravitational field literally is space-time, then you cannot say space is just a place that contains the physical universe (including fields). From your quote above: In that empty space beyond there will be no gravity or any other type of field because there will be no physical matter to generate any kind of field.

    If you agree that space-time has no existence independent of mass, then the statement is absurd. You cannot have an empty space where there are no fields, because space is just the geometric structure of the field itself. In that sense, space is not a place where things exist in, but it is just the geometry of the physical world itself.
  10. May 25, 2003 #9
    That does address my post when you wonder if space-time is the gravitational field. If they are one and the same, why would anyone wish to use a theatrical name like space-time instead of the categorical name of gravitational field? Using two name for the same phenomena is confusing to a lot of people who don't understand that space-time is not a physical thing. Many people talk about space-time as if it's a mystical underpinning of the universe, when in reality it is nothing but a mental conjuration that, in essence, means nothing.

    Why couldn't you have an empty space without fields? Are you suggesting that space doesn't exist until you put a planet someplace? If that's the case, how would you know where to put the planet? How do you define the space extant of a galaxy? And how is that space filled between one galaxy and the next galaxy closest to it?
  11. May 25, 2003 #10


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    A rather childish message it responded to...:wink:
  12. May 25, 2003 #11


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    Remember that concepts of space and time have been around long before relativity. Everyone is familiar with them, even without any knowledge of physics. Newton discovered the gravitational field, but it wasn't until Einstein that it and space-time were seen to be the same entity. Any term will work.

    Keeping in mind that the metric of the gravitational field is space-time, you can see how space has no independent existence. Everything in the universe produces a gravitational field, so even in the vast voids between galaxies there is gravity present. Take away the field, and space disappears.

    Likewise, location only has meaning within the field itself. Space-time in that sense, is not located anywhere, since location is defined only by geometric relations of the field. You could also say space-time is located everywhere, being found at each point in the manifold.
  13. May 25, 2003 #12
    If space has no independant existence, how can there be a place for a field to move into? There must be an empty place that exists for there to be a place for a physical thing to be positioned. Therefore, space must be larger than the universe because the universe needed an empty place for it to fit into at it's beginning.

    If there is gravity in the spaces between galaxies, then which bodies are producing the gravities which extend that far out into outer galactic space?
  14. May 25, 2003 #13


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    This is really semantics. There is no such thing as a "gravitational field," there is only the curvature of space-time. You could imagine a flat space-time, in which there would be no gravity. This is the space-time environment of the special relativistic theory, and is called Minkowski space-time.

    The idea that "space-time" = "gravitational field" is purely semantic -- especially considering that no one actually uses word "gravitational field" in physics. It's a word game.

    - Warren
  15. May 25, 2003 #14


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    That is a common misunderstanding, and it's based on bad logic and intuition. A manifold does not need to placed in any outside space in order to exist. In fact, any volume is defined entirely by it's own geometry, and needs no reference to any space outside the boundaries. So while everyday objects we experience are always embedded in some larger space, this is not true of space-time itself. Intuition makes visualizing this difficult, but intuition is not logic.

    And as I'm sure you know, all bodies have a gravitational pull on everything else. Even the field generated by a paper clip will reach the entire universe, and this goes back to the gravity of Newton. But it really is semantics as Chroot said. The important thing to note is that space is not some seperate medium in which matter resides.
    Last edited: May 25, 2003
  16. May 25, 2003 #15
    I see now where your idea of gravity breaks down. A paper clip, nor anything else, can project a gravity field to infinity. A galaxy's gravity field can only reach to a definite distance from it's mass. A larger galaxy will have a gravitational field which extends farther out into space than the gravity field of a smaller galaxy. The cumulative gravity field of a galaxy cluster will extend further than the gravity field of a smaller galaxy cluster. Gravity is unique in that it interacts with other gravity to form dominant regions where the greatest concentration of mass resides. Regardless of how gravity acts, it is a physical force which is produced by physical bodies, therefore it has a limitation of existence the same as any other physical object does, including light. That is just elementary physics. When you start clouding the physical reality with beliefs in infinity, you lose perspective.
  17. May 25, 2003 #16


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    Uh-huh... yes, Dr. John. Tell us more... I already put my tinfoil hat on, and am awaiting further instructions.

    - Warren
  18. May 26, 2003 #17
    Hear hear. Here we go again from malformed physical notions into plain religion.

    Please explain me then, what or who "puts" the universe anywhere?

    Don't you think this very assumption (universe having a beginning) is a wrong assumption?

    The universe is everywhere and everything. There is no "pre-existing space" in which "suddenly emerged a universe".

    The universe is simply matter in eternal motion. And with matter we mean any material notions that physcis thus far came up witt, such as massive particles/bodies, energy, waves, electrons, fields, Quantum mechanical waves, radition, protons, quarks, etc. etc.

    Matter is in motion always and matter cannot be seperated from motion. Space and time just denote the "modes of existence" of matter.
    That means: space and time do not exist as seperate physcial entities, but they are the way in which matter exists.
  19. May 26, 2003 #18
    Yes, and I think in the same way as you can not think of infinite space, neither you can think of infinite time, in that you require for all material forms to have had a "definite begin" in time..
    Your reasoning therefore starts out from a false assumption, that all of a sudden, a paperclip for instance "starts out" or "begins" and that the gravitational field of that thing begins to exist, and spreads out into space. Since the gravitational fields spreads out from the paperclip into surrounding space with a finite velocity, you then conclude the gravitational field of the paperclip always stretches out in a finite amount of space.

    Well this reasoning is obviously false, cause you just assumed that the paperclip suddenly emerged from nowhere into reality. We know however of no paperclip that "suddenly emerges" from nowhere into reality. We only know of paperclips in the way how they are formed from iron rods, and then bended to make this unique "paperclip form" into a real object. Well where does the iron come from? Also that did not suddenly emerge from nothing, but was digged out of the earth's core, and so far we know the earth itself and the iron, were just remnants of previous star explosions in which the iron formed, that formed the solar system, the sun and planets and moons and "space dust/rocks", asteroids and comets etc, that travel through or in the solar system. The star itself, which exploded and put out the heavier elements into space, neither did emerge from nothing, but was born out of clouds of gas, etc. etc.

    To put it briefly, the material which substitutes the material form we call paperclip, has always existed in whatever form or shape, since we can not denote of any begin of matter, and never saw anything material to have a "sudden emergence into reality" without a prior material form causing this emergence, since no matter can ever be created or destroyed. Hence it is not necesary for the gravitational field to have only a finite extend.

    Matter itself is infinite, which means that any concrete material form (wether it be a star, a galaxy, an atom, or whatever material constellation), which is always in a finite space and time extend, always denotes the transition from one (finite) material form into another (finite) material form, as a process which goes on without begin or end.

    Well I know this is not the end of the discussion, since it is argued from a cosmological point of view that all matter and also the gravitational field themselves emerged out of the Big Bang.
    This in itself is not a contradiction to the fact that matter does not have a begin or end, the Big Bang can be thought of a a large scale transformation of one material form into another, and what material form existed prior to the Big Bang is not completely cleared up, although some viable theories emerged which in principle can explain these facts (inflation theory for instance).
    Last edited: May 26, 2003
  20. May 26, 2003 #19
    I don’t understand the claim that space-time is the same as the gravitational field. As far as I understand General Relativity, the gravitational field is the same as the metric.

    When you use the Lagrangian formalism to minimalize the action and use all the fields on the manifold, the metric is also included. It is treated as one field as the others.

    From this point of view I can understand if someone says that the gravitational field is the metric. But space-time is something more than the metric, it is a differentiable manifold with a connection and a metric.

    You don’t use space-time as a field, e.g. in the Lagrangian formalism. If you would do that, this would mean you are considering also the connection and the manifold subject of variations to apply the principle of least action. This is not the case.

    So I claim that the gravitational field is not the same as space-time, but the same as the metric.

    Does this objection make sense or did I overlook something in this long thread?

  21. May 26, 2003 #20


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    Technically, at infinite range the strength of gravity would be zero. But so what?

    No, this is basic Newtonian gravity. Every object produces a field throughout the entirety of space, regardless of the objects size. The only difference is the strength of the field, or gravitational pull at any given point.

    If the above is true, I don't see how the physical limitation of gravity has anything to do with whether or not space has independent existence (as a place) or not.
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