Is Spacetime Truly Smooth or Discrete?

[physical1]

There is no nothing, the concept of Nothing is a misconception. Just because "nothing" works when you talk to your friends and children, doesn't mean that you can apply it in fundamental physics.

Where is the evidence that "nothing" exists? What is nothing? Where am I supposed to find it or evidence of its existence?

Hahahaha. Yes the question of what is "nothing" is something programmers often ask.

http://c2.com/cgi/wiki?NothingIsAnything"

p.s. if there is "no nothing" then how do you define "no". No is just another word for nothing. Double none and double nuttin!

 

[WaveJumper]

Hahahaha. Yes the question of what is "nothing" is something programmers often ask.

http://c2.com/cgi/wiki?NothingIsAnything"

p.s. if there is "no nothing" then how do you define "no". No is just another word for nothing. Double none and double nuttin!

If Brukner-Zeilinger Information Interpretation is true(as i beleive), something and nothing are all the same - they are information. There are no paradoxes related to space(the disappearance of space under certain conditions, universe's boundery conditions, something out of nothing, entanglement and Bell's theorem, Zeno-like paradoxes related to whether space is continuous vs discrete, the finely tuned initial conditions, etc.). There are no time paradoxes either - the flow of time, the arrow of time, the abscence of universal now, backwards in time qausations, etc.) Hence i define "nothing" as a wrong mental image that's useful for contrasting something against a 'nothing'. It may have to do with death; if we were immortals, we'd hardly ever come up with the notion of nothing. If the Information interpretation is right, "no nothing" has the same fundamental 'content' as "nothing", just in a different sequence of bits.

 

[p764rds]

Hahahaha. Yes the question of what is "nothing" is something programmers often ask.

There is a physical 'nothing' which is where you 'cannot place an object' (Democritus et al) and where 'God lives' as someone told me yesterday.

But in our space-time the real 'nothing is a piece of undefined space-time.
Between 0.008 plank lengths and .007 plank lengths is nothing because its not defined - simple.

 

[Pythagorean]

I don't think anyone really knows, at this point. It hasn't been proved either way, but we do know that if it's quantized it must be a pretty fine-grained quantization. Reiner Hedrich, for one, has written a number of papers on the idea of quantum spacetime.

If quantum mechanics is universally true, then it's quantized. If quantum gravity turns out true, then spacetime must be quantized, so gravitons would mean quantum spacetime. As would chronons, if you believe in quantum time, but that's pretty speculative at this point.

Right now most (non-QM) models start with an assumption of smoothness, but hey--a HD TV looks pretty smooth from a distance, but we all know there are pixels when you look closely enough. I'd like to see it proved one way or the other; I'm very curious to find out which way it comes out.

--Mike from Shreveport

Thank you for this straight forward reply! I was surprised to see this thread still going.

I would just like to add (to make sure the more credible philosophical replies in this thread don't go ignored) that it's not necessary that one or the other be universally true. As Frederik and DrFaustus had replied originally, it could just be that these models are forever doomed to be limited to their 'appropriate places'.

I think you and I understand each other though and this reply is more tailored to the line of thinking I was experiencing at the time I asked the question. I've flirted many times with the idea of quantized time, but I'm hoping to get this whole quantized space business sorted out first!

 

[p764rds]

I've flirted many times with the idea of quantized time, but I'm hoping to get this whole quantized space business sorted out first!

Time must be granular for the same reason that space must be granular - the reason is, that the precision of the metrics (space an time) cannot be infinite.

You can view this as cut-off, capping, renormalization in QFT parlance.

Or, better, viewed in informational terms - the amount of data to needed to locate 1 Planck length in space-time is a few kilobits. There must be a limit that prevents it from being many giga bytes. Why? too much data would not be able to be processed in the required time. That limit will be one of the constants for this universe.

(Zeilinger work is heading in that direction)

 

[Halcyon-on]

Time must be granular for the same reason that space must be granular.

This is surely true in your own universe. But in the real universe the only think that we can state for sure is that the energy-momentum is quantized (granular), not the space-time.

 

[aussie_mike]

I worked with an electronics engineer who was completing his PhD in Physics, and he was of the opinion that space time is granular. Quantum physics and Planck constants seem to imply this. The clincher for me is that at the tiniest level a particle goes from point A to point B without traveling through the "space" between the two. Does not that define spacetime as granular?

 

[Dmitry67]

I also made a mistake assuming that minimal length implies that space is something like an array of pixels. But it is wrong analogy.

 

[jeff_kosela]

i didnt read many,... of the forums but an idea that came to mind is, on the level of quantum physics, understanding that matter is energy, i would say, no form, or build up of matter would affect super-symmetry, so in a... equation valuing these properties, id say space time,(or decay...) is constant.

 

[d9090]

If the action of Mass is quantized, then so must be the action of a "particle" with Mass on Space-Time, and the action of Space-Time on a "particle" with Mass.

Continuous Space-Time makes the mathematics easier; discrete Space-Time is closer to a "realistic" theory were the "action" known as Gravitation actually described.

But don't mind me: I'm a kook who swore off "point particles" and "ponderous matter" for Lent years ago.

d.

ps. the whole "no-thing" thing this is amusing. Surely no Marvel comic fan is getting sucked into that one! No-prizes really do exist! But then if you toss the basic idea of "reality" or "existence" you might expect a little confusion here and there. :-)

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Emergence of Novelty: Bane of Reductionism
'As above' is not necessarily so 'below'.