Resolution of time?

Zombrex

Is there a limit to the "resolution" of time, in that if you scale down the size of the interval you are measuring (seconds to microseconds to nanoseconds etc etc) you get to an interval measurement where nothing can actually happen/change in between those intervals.

Son Goku

Yes, the planck time. It's around 10^-43 seconds.

Zombrex

Son Goku wrote:

Yes, the planck time. It's around 10^-43 seconds.

Cool, looked that up on Wikipedia. Very interesting. Cheers

Its amazing that they can work all this stuff out from models and maths.

Son Goku

Wicknight wrote:

Its amazing that they can work all this stuff out from models and maths.

You should see some other stuff that can be worked out. For instance there is a very simple arguement from which you can derive the existence of electromagnetism. That means you derive the whole force, its existence, equations and all from first principles. Not only can we model it, we can explain why it is there.

Most of theoretical physics is stuff like this. Finding strange facts that come about as a consequence of some simple little fact.

nesf

Son Goku wrote:

Most of theoretical physics is stuff like this. Finding strange facts that come about as a consequence of some simple little fact.

It's also got an awful lot of math in between the two...

Michael Collins

Son Goku wrote:

For instance there is a very simple arguement from which you can derive the existence of electromagnetism.

Any chance you could shed more light on this please Son?

Professor_Fink

Son Goku wrote:

Yes, the planck time. It's around 10^-43 seconds.

Actually we don't know that this is true. We know basically nothing about Planck scale physics.

For what it's worth, when dealing with the problem of measuring time in a regime where the uncertainty principle comes into play, it is usually useful to consider a quantum rotor rather than an actual clock. If you wish to time a particle passing between two points, A and B, you define the time taken in terms of the angle rotated through between these points rather than measuring when the particle crosses the start and finish lines. You can completely circumvent dangers of the uncertainty principle.

Another point worth noting is that Planck scale black holes evaporate really really fast, so the wikipedia argument is not exactly rigorous.

Zombrex

Isn't anything in theoretical quantum mechanics simple??!!??

Professor_Fink

Wicknight wrote:

Isn't anything in theoretical quantum mechanics simple??!!??

Sure, but this is the quantum gravity regime, which really isn't simple at all.

Son Goku

Professor_Fink wrote:

Actually we don't know that this is true. We know basically nothing about Planck scale physics.

Wicknight's question was about the shortest period of time which could experimentally be resolved. I know there might exist shorter periods of time, but even though we don't know anything about quantum gravitational physics wouldn't the experimental arguements for not resolving processes faster than this time be unchanged? Unless I have it wrong.
Not that we can resolve processes anywhere near this fast currently.

However to be clear, the Planck time is a generic feature of most quantum gravity theories, but Professor Fink is correct in saying that this is not a solid arguement for it existing.

Son Goku

Michael Collins wrote:

Any chance you could shed more light on this please Son?

Sure, just let me think of an analogy.

Professor_Fink

Son Goku wrote:

I know there might exist shorter periods of time, but even though we don't know anything about quantum gravitational physics wouldn't the experimental arguements for not resolving processes faster than this time be unchanged? Unless I have it wrong.
Not that we can resolve processes anywhere near this fast currently.

That's not clear to me at all. It's not at all clear that the Schwarzschild solution is applicable, and even if there is, then quantum imaging might provide a higher resolution.

(Quantum imaging uses entangled photons to achieve high spatial resolution using less power by making use of entangled photons)

Son Goku wrote:

However to be clear, the Planck time is a generic feature of most quantum gravity theories, but Professor Fink is correct in saying that this is not a solid arguement for it existing.

It's inevitable that it will be a feature of quantum gravity, since it is precisely the scale at which we expect quantum gravity to have a significant effect. That's not to say that it must provide a fundamental limit on the resolution of time, length, mass, etc., but rather the characteristic scales at which quantum gravity effects become important.

Son Goku

That's not clear to me at all. It's not at all clear that the Schwarzschild solution is applicable, and even if there is, then quantum imaging might provide a higher resolution.

(Quantum imaging uses entangled photons to achieve high spatial resolution using less power by making use of entangled photons)

Fair enough. Just goes to show you can't just say the stuff you're used to hearing, e.g. "The Planck time is the shortest time".

ZorbaTehZ

It's threads like this that make me sad I'm not doing something Physic-y in college

dan719

ZorbaTehZ wrote:

It's threads like this that make me sad I'm not doing something Physic-y in college

I don't know- it's kinda making me sad I am.:o

Son Goku

Michael Collins wrote:

Any chance you could shed more light on this please Son?

Sorry for the delay.

Basically in modern physics the electron is seen as being a small quantized excitation of a massive "electron field" that fills the whole universe.

Now as you know many objects have symmetries such as a football which looks the same no matter what way you rotate it. This is a symmetry in that it doesn't effect the physics of the ball. For instance it makes no difference if I rotate a ball 90 degrees before you kick it because of its spherical symmetry.
This might seem a bit odd, but the electron field also has a symmetry like this called a gauge symmetry. It's a bit more abstract, but the electron field can be multiplied by a complex number at each point and it makes no difference to what happens physically.
However the electron field on its own can't do this, it needs another field to "help" it not be affected by complex numbers. If you work through the mathematics you can try to derive what this other field is like. It turns out this field is the electromagnetic field.

If anybody knows economics there is an almost perfect analogy. Imagine if somebody were to mess up the world markets by making incomes and prices jump around randomly. This would cause supply and demand to go out of hand. Some people would try to buy more than there is supply for and others wouldn't be able to afford their previous standard of living. However this brings in the "Invisible hand of the market". As time goes on prices will adjust, decreasing and increasing there until all markets once again clear, compensating for the random changes. The "invisible hand of the market" restores order.

In this analogy incomes and prices are the electron field, the random jumping is like the multiplication by a complex number and the "invisible hand of the market" is the electromagnetic force.

Basically electromagnetism exists to make sure matter doesn't care about multiplication by a complex number.