Question about spatial dimensions

Started by Tzeentch._2 pages
Tzeentch._ #gottem

Wow, this is a man's thread.

Lestov16 CTU Field Agent

Originally posted by Astner
No, the Planck length and the Planck time are definitely constants, that's not the question. The question is regarding their significance.

All the Planck length and Planck time are, as far as the standard model is concerned, are the shortest units of length and time measurable.

Even so, half a Planck length and half a Planck time are definitely existing scales, you just wouldn't be able to make any meaningful measurements at those scales according to the standard theory.

Exactly. This is what I mean. Measuring an object "paused" at one Planck time is the closest we can get to a 3D measurement inside the 4th dimension, as an object that is purely 3D doesn't exist in time, and thus wouldn't exist in our 4d universe.

Lestov16 CTU Field Agent
Originally posted by Tzeentch._
Wow, this is a man's thread.
Astner The Ghost Who Walks

Originally posted by Lestov16
Exactly. This is what I mean. Measuring an object "paused" at one Planck time is the [b]closest we can get to a 3D measurement inside the 4th dimension,[/b]

No, it's the closest we could measure with the standard theory. It's not a pause, it's an interval on the space-time continuum just like a minute would be an interval on the space-time continuum.

Originally posted by Lestov16
as an object that is purely 3D doesn't exist in time,

Just because we can't measure it doesn't mean that it doesn't exist.

A dimensional construct is simply a mathematical model to explain and relate the laws of nature. Nothing more.

Lestov16 CTU Field Agent
Originally posted by Astner
A dimensional construct is simply a mathematical model to explain and relate the laws of nature. Nothing more.

I understand what you mean. Would you happen to know anything about Tegmark's Ultimate Ensemble theory?

Mindship Snap out of it.

Originally posted by Astner
Our models are incomplete. That's all there is to it.
Yeah, bummer that.

Originally posted by Astner
But I don't understand from where you got the foam to froth. Because that has to be one of the most meaningless and unrelated illustrations of the Friedmann models I've ever heard.
As much as I'd like to take credit for breaking new ground, I'm gonna blame google. Eg, if one googles 'quantum foam', you get stuff like...

http://www.universetoday.com/61011/quantum-foam/

Astner The Ghost Who Walks

Originally posted by Lestov16
I understand what you mean. Would you happen to know anything about Tegmark's Ultimate Ensemble theory?

It's not a theory, it's a statement. An unverifiable hypothesis and a nonsensical one at that, as physics only describes how certain phenomena behave and relate to one another under managed conditions, and not why.

Originally posted by Mindship
As much as I'd like to take credit for breaking new ground, I'm gonna blame google. Eg, if one googles 'quantum foam', you get stuff like...

http://www.universetoday.com/61011/quantum-foam/


So what you meant was that since we can't measure it it doesn't exist? Yeah, that sounds like philosophical drivel to me.

Mindship Snap out of it.

Originally posted by Astner
So what you meant was that since we can't measure it it doesn't exist?
Laddie, that's the last thing I'd be sayin'. Simply put, in a nutshell, I was looking for a context in which subplanck "made sense," theoretcially or otherwise -- and I don't mean like 1.5 Planck time, but something like 0.5 Planck time. Theoretically, what phenomena (if any) are being considered in that context (other than, say, the time it takes light to travel less than a Planck length)? Eg, how long does it take a virtual particle to pop into existence -- not appear/disappear, just appear?

Astner The Ghost Who Walks

Originally posted by Mindship
Laddie, that's the last thing I'd be sayin'. Simply put, in a nutshell, I was looking for a context in which subplanck "made sense," theoretcially or otherwise -- and I don't mean like 1.5 Planck time, but something like 0.5 Planck time. Theoretically, what phenomena (if any) are being considered in that context (other than, say, the time it takes light to travel less than a Planck length)?

Phenomena in quantum field theory? None.

Originally posted by Mindship
Eg, how long does it take a virtual particle to pop into existence -- not appear/disappear, just appear?

That depends on how you clock it as well as the initial conditions. Pair production is phenomena resulting from interactions with particles that are already there.

Mindship Snap out of it.

Originally posted by Astner
Phenomena in quantum field theory? None.
What about the more 'esoteric' theories, for example, string or brane?

Btw, thanks for your answers. This stuff fascinates the hell out of me.

Astner The Ghost Who Walks

You mean quantum gravity theories, i.e. beyond the standard model?

In string theory specifically it you couldn't measure it because the frequency of the strings is one Planck length.

The ADD model implies smaller scales if that's what you're after.

Mindship Snap out of it.

Originally posted by Astner
You mean quantum gravity theories, i.e. beyond the standard model?
Yes.

Originally posted by Astner
In string theory specifically it you couldn't measure it because the frequency of the strings is one Planck length.
Noted.

Originally posted by Astner
The ADD model implies smaller scales if that's what you're after.
It's a good place for me to start trying to wrap my head around this stuff (and likely fail miserably). Merci.

Lestov16 CTU Field Agent

Would a 3D object be considered one at absolute zero?

Astner The Ghost Who Walks

Originally posted by Lestov16
Would a 3D object be considered one at absolute zero?

Yes, temperature doesn't affect the dimensionality of an object in any model. It would be a nonsensical extrapolation.