# Elementary time - how does it work?

1. May 26, 2012

### klaapbakken

I just read some stuff about elementary time, or planck time, but I'm not entirely sure if I got what that was all about.

Does the existence of planck time imply that something will always be moving one planck length at a time, and can't exist between the start and the end of a planck length, or does it simply mean that it can be there, but we can't measure it?

And, for the record, I don't really have any idea what I'm talking about, so if this doesn't make sense, let me know.

2. May 26, 2012

### phinds

I believe that "Plank Time" is just a specific "distance" in time, and it is WAYYYY below what we can measure. There is no evidence yet, one way or another as to whether or not time is continuous or discrete, and if it IS discrete, whether the "Plank Time" is the fundamental unit. It's an area of speculation in physics today, although you'll find proponents on both sides, with most saying either it's continuous or we can't tell, and fewer saying it's discrete, but this is mostly because continuous seems more natural (a VERY bad way to decide things at the quantum level) and there is no evidence for discrete.

3. May 26, 2012

### Staff: Mentor

The planck units are just regions where gravity gets strong: If two particles with approximately planck energy collide, the gravitational interaction has a similar strength as the other forces. If you want to measure times/lenghts with a precision of the planck time/length, you need an energy of the order of the planck energy involved somewhere. Again, gravitation gets important there.

The issue with gravitation: We don't have a (useful) quantum theory of gravitation yet, and we cannot predict how the other forces behave at this energy. Maybe all the fundamental forces are just different forms of a more fundamental, universal force, which becomes important somewhere at the planck scale. Maybe something else happens... we don't know.

4. May 26, 2012

### klaapbakken

I see. According to Wikipedia, regarding planck time: "Theoretically, this is the smallest time measurement that will ever be possible." This is what got me wondering whether it also was the smallest possible unit of time.

And by the way, if planck time is indeed the smallest possible unit of time, am I right in thinking there would have to an undividable unit of length aswell? c*tP?

5. May 26, 2012

### klaapbakken

Interesting, thanks for the input. I see that I need to do some more reading on the planck units!

6. Oct 3, 2012

### spndr7

Is maximum possible speed the minimum also ?

This question also struck me.As to the definition 1 Planck length/Planck time is the highest possible speed that is speed of light c.
But minimum length to moved in one quantum of time is 1 planck length,how could be the minimum possible speed the maximum ?

planck scale (pdf)