question about planck lengths/quantized space and expanding space?


by jeebs
Tags: expanding, lengths or quantized, planck, space
jeebs
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#1
Nov27-11, 01:47 PM
P: 326
If I'm not mistaken, it is thought that space is divided up into quantized little indivisible chunks, the size of which is called the Planck length.

Also, the space of the universe is thought to be expanding. We could have 2 objects stationary relative to one another at some time t_0, then allow space to expand from t_0 to t_max, and these 2 objects would then be at a greater separation.

Does this mean that each little block of space is itself stretching out (ie. the 2 objects have the same number of blocks between them at t_0 and at t_max)?

Or, is it that they stay the same size, but more blocks exist between the 2 objects at t_max than there were originally at t_0?
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nucl34rgg
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#2
Nov27-11, 01:58 PM
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I think most mainstream modern theories of physics treat spacetime as continuous. There are some things like LQG which treat spacetime as discrete I think. Here's a good link.

http://physics.stackexchange.com/que...are-continuous
jeebs
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#3
Nov27-11, 02:01 PM
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Quote Quote by nucl34rgg View Post
I think most mainstream modern theories of physics treat spacetime as continuous. There are some things like LQG which treat spacetime as discrete I think. Here's a good link.

http://physics.stackexchange.com/que...are-continuous
ah, so I actually am mistaken?

Bill_K
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#4
Nov27-11, 03:12 PM
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question about planck lengths/quantized space and expanding space?


That's right, the Planck length is simply an order-of-magnitude length scale √(ħG/c3) at which both gravitational and quantum effects become dominant. There is so far no successful theory of what happens at that scale. Presumably the simple concept of continuous spacetime will no longer apply, but whatever replaces it must be rather complicated.
jeebs
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#5
Nov27-11, 06:08 PM
P: 326
hmmm, this will teach me to take what I read on random internet sites seriously without checking for proper peer reviewed papers. There are so many sites out there that paint this idea of quantized blocks of space as fact.
granpa
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#6
Nov28-11, 12:24 AM
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Quote Quote by jeebs View Post
If I'm not mistaken, it is thought that space is divided up into quantized little indivisible chunks, the size of which is called the Planck length.

Also, the space of the universe is thought to be expanding. We could have 2 objects stationary relative to one another at some time t_0, then allow space to expand from t_0 to t_max, and these 2 objects would then be at a greater separation.

Does this mean that each little block of space is itself stretching out (ie. the 2 objects have the same number of blocks between them at t_0 and at t_max)?

Or, is it that they stay the same size, but more blocks exist between the 2 objects at t_max than there were originally at t_0?
the problem disappears if our expanding universe is embedded in a larger 4D static hyperverse.

just sayin
jeebs
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#7
Nov28-11, 09:42 AM
P: 326
Quote Quote by granpa View Post
the problem disappears if our expanding universe is embedded in a larger 4D static hyperverse.

just sayin
I'll have to take your word on that because this means very little to me...
jsirak2
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#8
Feb8-12, 03:40 AM
P: 3
This is something that i am interested in becasue i recently read that a new theory states that "that space is divided up into quantized little indivisible chunks, the size of which is called the Planck length." I am currently trying to re-find that article.

Is this some new theory with no information or is this something just for us simple mountain men like myself to pass time and sell magazines?
rai linga
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#9
Mar9-12, 02:14 AM
P: 20
I have a question about Planck length as the length of a string in String Theory. I understand that a string can be wound in a spiral and, apparently, the Cylinder thus formed will have a circumference of Planck length. At the same time, of course, we've two-dimensionally created a Circle with Planck length as its circumference. But such a circle must then have a diameter that is smaller than Planck length ---and yet there can be no measurement below Planck length. To restate the dilemma, given that the size of a circle is always its diameter, it seems as if we're now find ourselves speaking paradoxically in the form of Buddhist koan ----Can there exist a circle that has no size? (What am I missing here? Help!)


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