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Old 08-02-2003, 11:04 PM   #51
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Sorry for the late reply.

Quote:
Originally posted by excreationist





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Originally posted by jpbrooks
.....the successes of geometry (and the sciences that make use of it) seem to give us no reason to believe that space-time is not a continuum.

From PhysLink.com:

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The Planck length is the scale at which classical ideas about gravity and space-time cease to be valid, and quantum effects dominate. This is the 'quantum of length', the smallest measurement of length with any meaning.
And roughly equal to 1.6 x 10^-35 m or about 10^-20 times the size of a proton.
The Planck time is the time it would take a photon travelling at the speed of light to across a distance equal to the Planck length. This is the 'quantum of time', the smallest measurement of time that has any meaning, and is equal to 10^-43 seconds. No smaller division of time has any meaning. With in the framework of the laws of physics as we understand them today, we can say only that the universe came into existence when it already had an age of 10^-43 seconds.

Thanks for the quote and the clarification, excreationist.

What this suggests to me is that one must make a distinction between that which has "meaning" within the more specific context of quantum physics and that which has general meaning in the physical world. It has to make sense to assume, for example, that photons can and do travel through intervening space. at any arbitrary location in space, when they are travelling a distance along an interval equal to the Planck length, otherwise the whole concept of a "smallest" meaningful time or distance itself becomes arbitrary and meaningless. The whole concept depends on the time that it takes for a photon to travel from one point in space to another. But the concept becomes meaningless if a photon can "leap" from one point to another without traversing any intervening space.

But since it must be assumed that the photon traverses the intervening space, it makes (general physical) sense to assume that there are divisions of length (and as a logical consequence, divisions of time), smaller than the Planck values.

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It doesn't say whether space is therefore in a square/cubic pixelated form... BTW, a honeycomb layout (with hexagons) are an equal distance from adjacent cells. That's 2-D though, but there could be a 3-D form of that... (like how you can stack spheres to make a triangular pyramid.)

This is certainly interesting to contemplate. and I do understand your point about what is meaningful from the standpoint of QM, but it just seems like we're putting a kind of discreet (pixilated) "grid" over space-time and stipulating that we must always think of the "grid" rather than the space-time that lies "underneath" the "grid" as the "real" 3-D space-time.
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Old 08-03-2003, 09:21 AM   #52
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jpbrooks:
Like you've said, it appears to be intuitive that things should pass continuously through space and time rather than do it in jumps... I'm not sure what the Planck length and Planck time are supposed to mean in reality... maybe theoretical physicists are saying that things do jump through space and time rather than pass through them continuously.... and I'm not sure if they think space is like a grid - or more like a honeycomb - or more chaotic/fuzzy.
Just because something is intuitive it doesn't prove it is so, especially when you're dealing with quantum physics. Though on the other hand, I don't know if it has been proven that spacetime is discrete either...
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Old 08-03-2003, 07:21 PM   #53
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Excreationist says:
Quote:
It appears to be intuitive that things should pass continuously through space and time rather than do it in jumps...
And it’s intuitive that the sun also rises. Intuition has proven an unreliable guide to the nature of nature.

Quote:
Maybe theoretical physicists are saying that things do jump through space and time rather than pass through them continuously.
No. Things do not jump through space and time but rather reappear in a different part of space at a different time. If space were continuous, what would be the point of particles jumping through it? No, the concept of jumping is based upon the concept of space not being continuous. Ergo, the appearance of them “jumping.”

Of course, these relatively recent discoveries in particle physics conform nicely with the Cathholic concept that creation is continuously being created and is not the once upon a time watchmaker’s creation wound up and subsequently left to wind down as the deists thought. – Sincerely, Albert the Traditional Catholic
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