Is time still undoubtedly continuous?

[Smiles302]

When you combine general relativity and quantum mechanics theory, does time become quantised?

Or are there any theories where this is a possibility?

We're doing both special relativity and quantum mechanics at the moment, in different modules, both lecturers make passing references to the more advanced bits and pieces then tell us not to think about it too much.

While leaving me unable to think about much else.

So is time always continuous as Newton imagined? Or are there some theories where it no longer is?

(Even if you think the theory is useless/pointless, once it makes some sort of mathematical sense, I'd like to attempt to read about it)

 

[khemist]

Time is continuous, that is an assumption in stating that it has a continuous derivative (i think).

Time is not, however, absolute.

 

[Penn.6-5000]

Time isn't "undoubtedly" anything; there is not yet a scientific consensus on how to unite general relativity with quantum mechanics. The modern presentation of quantum electrodynamics regards time as continuous, but it isn't compatible with general relativity. The string theories assume that time is continuous. Spin-foam based theories like loop quantum gravity quantize spacetime. We don't have proof either way, so at present the continuity of time is an open question.

 

[edgepflow]

Quantum mechanics suggest that time comes in "packets" of size equal to the Planck time (10^-43 seconds). Thus, the smallest increment of time, according to this theory, is 10^-43 seconds.

 

[khemist]

Did not know that thanks for the info.

Could anyone point me towards something describing the quantization of time?

 

[Penn.6-5000]

Quantum mechanics suggest that time comes in "packets" of size equal to the Planck time (10^-43 seconds).

Careful, there. While it's true that quantum mechanics is named after 'quantization,' it isn't quite true that everything is quantized. Mr. Khemist got it right three posts back when he remarked that the standard formulation of quantum mechanics requires you to be able to take a derivative with respect to time, and you can't do that unless time is continuous. Loop quantum gravity and the other spin-foam theories do "quantize" time by making a little mesh of interconnected points of spacetime, but at this time such models are speculative. Standard, run-of-the-mill quantum mechanics still requires continuous time.

 

[khemist]

Loop quantum gravity and the other spin-foam theories do "quantize" time by making a little mesh of interconnected points of spacetime, but at this time such models are speculative.

Does that imply that the space itself is quantized in those theories?

 

[edgepflow]

Careful, there. While it's true that quantum mechanics is named after 'quantization,' it isn't quite true that everything is quantized. Mr. Khemist got it right three posts back when he remarked that the standard formulation of quantum mechanics requires you to be able to take a derivative with respect to time, and you can't do that unless time is continuous. Loop quantum gravity and the other spin-foam theories do "quantize" time by making a little mesh of interconnected points of spacetime, but at this time such models are speculative. Standard, run-of-the-mill quantum mechanics still requires continuous time.

OK, thanks for the viewpoint. I recall a journal article I read on quantum cosmology that concluded the probability of finding the initial early universe at a time less than the Planck time was zero. This got me thinking time was only provided by nature in increments of the Planck time. I am totally open minded to this stuff.

 

[Smiles302]

Ooo thanks everyone! =D I am going to do some reading on Loop Quantum Gravity then.

 

[granpa]

the standard formulation of quantum mechanics requires you to be able to take a derivative with respect to time, and you can't do that unless time is continuous.

you can't find dx/dt if time isn't continuous but you can perfectly well find Δx/Δt

 

[Smiles302]

I always assumed discrete calculus allowed for finding the dx/dt where x and t don't need to be continues.
I've never taken it as a module. It just would have been one of my options had I kept up maths.