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Old January 18 2013, 08:34 AM   #1
Gary7
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Basic Science Question - "fabric" of space

If there are any hard science people out there on TBBS that might browse this sub forum, please take a moment to comment here if you don't mind. I have a very, very basic question about the "fabric of the universe".

When you read about gravitational theories, there is often the postulation that there isn't any gravitational force per se, but instead that space is "curved", relative to the mass of the objects within it. A typical demonstration of this is a stretchy fabric pulled taut over a bucket. You put a heavy marble in the middle and then you observe a symmetrical semi-conical sagging towards the center. Rolling another smaller spherical object on the material causes it to "orbit" the center object. This is supposed to simulate how gravity actually works.

So then there's the "fabric" notion. Well, I find the word mystifying because fabric suggests a tangible substance that can be felt. Clearly, there is no such "visible" fabric. So then is it invisible or "dark matter"? Yet, if that is the case, couldn't we detect it in some way when pointing sensors at the moon? That between the Earth and the moon there must be some measurable amount of "fabric" there?

What always gets me about this concept is this: Space is a vacuum. Emptiness. That between the Earth and the moon, there might be some dust or debris floating about, maybe even a comet or asteroid, but discounting those it's empty space. NOTHING THERE. So where's this "fabric"?

In my mind, in order for there to be any warping, there must be something to be warped. Some detectable mass. But when "dark matter" is mentioned, it's in a very nebulous manner... that it's some "background" constituent in deep space. Still... for there to be sufficient gravitational force to cause objects to swing into orbit around the Earth, certainly that mass should be substantial enough to cause the effect and thus be detectable in some manner akin to how we detect other matter. Right?


Anyway, I haven't yet found any explanation that makes sense to me. Anyone care to shed light? Much appreciated!
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