Do time and space occur in quantum units?

[arcadesonfire]

Hi folks, I've never taken a real quantum physics course, so this question miiight be really silly, but here it is:

I'm wondering if there's any research going on or any established theories about time and space themselves occurring in quantum units rather than occurring in a continuum that can be divided over and over ad infinitum.

In other words, can a quantum particle exist anywhere, or is there evidence suggesting that it must exist at a quantifiable point on a space/time grid?

Or is there strong evidence or proof that space/time are definitely continuums where there's always a position between any two points?

Anyone ever run across any discussions of this or have any suggestions for things i should read?

Thanks!

 

[geophysics10]

There is no evidence showing that space or time are discreet units. According to General Relativity, a particle moves continuously through space-time (space and time). These are both relative units and have no meaning outside of a relativistic context. Depending on the relative energy of 2 particles, the distances between the two (when choosing the right frame of reference) range from ~0 (at velocities ~c) to the resting distance d (where v' [the relative velocity] = 0).

However, there is work being done to quantize space-time in order to simplify physical problems with space-time at and smaller than the Planck scale. Quantum field theory breaks down at the Planck scale and this is the driving force and one of the final problems in coming up with a TOE (theory of everything). This is one of the instances when QM and Relativity clash.

**It's difficult (understatement) to probe into smaller and smaller information (Planck constant) about time/distance, mass/energy, etc. Just as its very difficult to probe light without mucking up your results (e.g. slit test).

At the current state of things, its impossible to tell if space-time is continuous or not at very small scales. Just as the mechanisms which cause randomness in QM are not explained, whether its turtles all the way down, whether there is an infinite universe or pink dragons just out of our line-of-sight, it's generally physics taboo to project your own opinions about "whats going on behind the scenes" without evidence of any kind.

I think that often times personal taste influences the understanding of physics. I've been guilty of it many times myself.

String theory (bleh) is taking a stab at quantum gravity, there is loop theory, and a whole muddled up mess of other things to confuse the crap out of everyone on the topic of 'how small is the smallest'.

Check out Wikipedia for a start:
http://en.wikipedia.org/wiki/Quantum_spacetime

 

[Simfish]

Isn't there a debate about this? About Planck time (http://en.wikipedia.org/wiki/Planck_time) and Planck length? Anyways, such theories will be very difficult to empirically verify.

 

[geophysics10]

Isn't there a debate about this? About Planck time (http://en.wikipedia.org/wiki/Planck_time) and Planck length? Anyways, such theories will be very difficult to empirically verify.

Agreed. Just throwing what information I had at him.

 

[granpa]

http://en.wikipedia.org/wiki/Doubly-special_relativity

In principle, it seems difficult to incorporate an invariant length magnitude in a theory which preserves Lorentz invariance due to Lorentz-FitzGerald contraction, but in the same way that Special Relativity incorporates an invariant velocity by modifying the high-velocity behavior of Galilean transformations, DSR modifies Lorentz transformations at small distances (large energies) in such a way to admit a length invariant scale (planck length) without destroying the principle of relativity. The postulates on which DSR theories are constructed are:

1. The principle of relativity holds, i.e. equivalence of all inertial observers.
2. There are two observer-independent scales: the speed of light, c, and a length (energy) scale λ (η = 1 / λ) in such a way that when λ → 0 (η → ∞), special relativity is recovered

 

[arcadesonfire]

Thanks for all the replies folks. I've got a lot to read up on to understand the things being researched. I had been wondering if any minimal limits (like Planck) were interpreted as signs that time/space had to be discreetly quantifiable, but then again, even if we couldn't see between one point and another, that doesn't mean there isn't something between...

But at the moment, i think i don't even have a good enough understanding of the contemporary quantum and relativity theories to frame my wonderings correctly. So i'll be researching all the things you've brought to my attention.

Thanks again!

 

[granpa]

this article was being discussed in all the forums recently
http://www.sciencemag.org/content/301/5637/1169.1.summary

 

[tom.stoer]

a good place to start reading and to ask questions is here in the "beyond" forum https://www.physicsforums.com/forumdisplay.php?f=66

there are both string theory and loop quantum gravity discussions (as well as other topics related to quantum gravity research programs)