# Can time be quantized?

1. Aug 21, 2011

### conner.ubert

Is the quantization of time possible? Maybe then again maybe not.

~This post is not for those who believe that time is a creation of the human imagination~

2. Aug 22, 2011

### Galron

Time is quantised already as time-space.

Motion relativistically gives us the quantisation of any point in space relative to any other in the co-ordinate frame of x,y,z,t or i if you like.

There is no absolute time, but there is a relative time to which we will all agree.

3. Aug 22, 2011

### kdbnlin78

Currently there is no theory to suggest that time can be quantized. However, in order that a theory of "Quantum Gravity" to exist, that is, the cohesion between Quantum Physics and Gravitiation, there is a suggestion that this may be achievable if one were to quantize time as it were.

A nice way of looking at quantized time is to consider a theory of Loop Quantum Gravity. Loop quantum gravity theorizes a space that can be viewed as a fine fabric of finite quantised loops of excited gravitational fields called spin networks.

When viewed over time, spin networks are called spin foam. A major quantum gravity contender with string theory, loop quantum gravity incorporates general relativity without needing string theory's higher dimensions.

Here quantized spacetime is a superposition of an infinite amount of spin networks.

4. Aug 22, 2011

### yoda jedi

if space-time is continuous, no possibilty.

5. Aug 23, 2011

### maverick_starstrider

I seem to vaguely remember a quasi-drunken conversation with a cosmologist where I essentially asked this and I think I remember him saying that if you have any quantization of time (no matter how small the quanta) you will get violations of lorentz invariance that should be detectable at currently accessible experimental ranges but we don't see them. I have no reference and I may be flat out wrong though.

I believe that the name for theories where both space and time are quantized are called "Doubly Special Relativity" theories

6. Aug 23, 2011

### yoda jedi

and loop theory.

.

7. Aug 23, 2011

### nouveau_riche

if time is to quantized then in order to define events or anything in places with zero time ,there shouldn't be anything changing,it will be a place of non interactions,and if it does so you probably will not be able to observe it

8. Aug 23, 2011

### edpell

from wikipedia

One Planck time is the time it would take a photon travelling at the speed of light to cross a distance equal to one Planck length. Theoretically, this is the smallest time measurement that will ever be possible,[3] roughly 10E−43 seconds. Within the framework of the laws of physics as we understand them today, for times less than one Planck time apart, we can neither measure nor detect any change. As of May 2010, the smallest time interval that was directly measured was on the order of 12 attoseconds (12 × 10E−18 seconds),[4] about 10E24 times larger than the Planck time.

9. Aug 23, 2011

### Galron

Ah I'm sorry I kinda got the wrong end of the stick there. Apologies guys. I would delete my post but it's too old.

10. Aug 23, 2011

### jfy4

Lets assume there is a smallest length (time), $l_p$, then at first glance, this appears to violate lorentz invariance, but it doesn't. Pretend there is some length operator
$$\hat{l_p}|l_p\rangle=l_p|l_p\rangle$$
with fundamental length eigenvalue $l_p$. Then indeed this is the same regardless of the observer, but that is not a violation of lorentz invariance, because quantum tells us that quantity should not change from observer to observer, but rather the expectation value $\langle l_p\rangle$ is an observer dependent quantity. And indeed the expectation value would vary from frame to frame.

Therefore if you treat the quantization of space-time, not only relativistically, but also quantum mechanically, there is no violation.

11. Aug 23, 2011

### jfy4

I would say that PF is not the place to put forth your individual theories, except, what you wrote is a crude start to general relativity, the current theory of gravity. Having particles does not imply time is quantized. The particles you referred to seem to me, more or less, like normal particles on space-time world-lines. This is just like the current model, but just because particles move though time doesn't say anything about how space and time are quantized...

It's good you are thinking about these things, but you should consider the following:
quantum gravity will describe the evolution of the gravitation field at the quantum scale, not the (quantum) dynamics of particles on curved spacetime (although the two go hand-in-hand); the later is general relativistic quantum mechanics, not quantum gravity.

12. Aug 24, 2011

### ZapperZ

Staff Emeritus