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AtomicJoe
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What is the shortest distance you (or anything) and travel?
Is there a limit?
And if so why?
Is there a limit?
And if so why?
I can't even figure out what that means! What do you mean by "measure" a distanced and what do you mean by "travel" a distance?AtomicJoe said:That says shortest measurable distance also there are no references for it.
Just because you can't measure a shorter distance does not mean you can't travel a shorter distance?
HallsofIvy said:I can't even figure out what that means! What do you mean by "measure" a distanced and what do you mean by "travel" a distance?
bp_psy said:Doesn't the concept of spatial position and movement become indefinite long before the plank length due to the uncertainty principle?
Curl said:The point is that "space" and "movement" is nothing like you are familiar with when you go down to the quantum level. It is better explained by the wavefunction which is where the HUP comes from.
So asking "measure a small distance" turns out to be an invalid question at those lengths.
AtomicJoe said:I really do not see that it makes any difference I mean basically if you move something which is " nothing like you are familiar with" then it is "nothing like you are familiar with" in a different place".
I mean we move things everyday which are full of fundamentalist particles without any problem.
Pengwuino said:You don't see how the movement occurs at the [tex]10^{-35}m[/tex] scale, however.
Think of it this way, let's say you have a grid of tiles on the floor and someone wants to move across them and they're all 1'x1' and you're looking at this person way up in the sky. Now, the person can continuously move himself across those 1x1 tiles. He can make a movement that is so slight that the doesn't change his position to a neighboring tile (let's say he only moves an inch).
At the Planck level, this notion no longer is valid. "Small movements" such as in the previous example do not exist. It is also something fundamental, it is not just an issue with our experimental abilities. The guy in the previous paragraph could use a telescope to try to get a better measurement of how the guy is moving with a finer resolution than the 1'x1' tiles because the guy on the tiles can make seemingly continuous motions. At the quantum/planck level, such ideas are meaningless. Everything is discrete.
AtomicJoe said:So say use a force and apply it to an object and it moves one plank distance, what happens if I apply the same force to an object with twice the mass, does it move or not?
Pengwuino said:The problem is you're trying to use classical macroscopic ideas to deduce what can happen at scales where classical physics fails immensely. Everything is quantized. At some point, what you call a force can no longer be arbitrarily cut in half as well.
Gabe21 said:yes. just because u can't measure the distance doesn't mean it didn't move.
Okay, what reason do you have to think that?AtomicJoe said:Well measure is what it says, measure or detect, travel means to move.
I think you can move a distance which you can't measure.
HallsofIvy said:Okay, what reason do you have to think that?
The above is right in a metaphysical sense or from a realist's point of view, but, within the framework of current physics, you can never tell if something moved a distance smaller than Planck's length and thus it becomes meaningless, in terms of physics, to ask if something can "really" move a smaller distance. Maybe it can, maybe it can't; physics can't tell you, so, for physics a smaller distance doesn't exist (as of yet, of course).Gabe21 said:just because u can't measure the distance doesn't mean it didn't move.
saim_ said:The force applied will accelerate the particle and deform its wave-packet or its probability distribution function. Taking approximation of the gravitational effects of the energies involved into account will further blur our view of the position and velocity of the particle. Things are not so simple at quantum scales.
http://rugth30.phys.rug.nl/quantummechanics/potential.htm
http://en.wikipedia.org/wiki/Uncertainty_principle
saim_ said:You are extrapolating the classical picture to the quantum scales, which is completely wrong. Nothing is holding the particle in place; its position cannot be determined due to its wave-y uncertain nature even at scales much larger than Planck's length. But in theory, yes you can measure its position precisely at such length if you completely give up information regarding some other quantities. But if you go down to Planck's scale, you cannot even do that due to gravitational effects.
I think this discussion will do more harm to your understanding than good. So I suggest reading up a little bit on quantum mechanics and then look back at this matter.
Gabe21 said:yes. just because u can't measure the distance doesn't mean it didn't move.
Quantum physics is what happens in the real world.Classical mechanics has a much more limited scope.AtomicJoe said:The classical position has to be reconciled with the quantum position because that is what happens in the real world.
I know absolutely nothing about Quantum Mechanics. But isn't Newtonian idea of force just a macroscopic observation of just the fundamental forces? I mean when we apply force on something through contact, at the atomic level it is the electromagnetic repulsive force that causes the body to move isn't it. F=ma only applies for big bodies. But at extremely small distances such as the subatomic scale these things do not hold.AtomicJoe said:So say use a force and apply it to an object and it moves one plank distance, what happens if I apply the same force to an object with twice the mass, does it move or not?
mishrashubham said:I know absolutely nothing about Quantum Mechanics. But isn't Newtonian idea of force just a macroscopic observation of just the fundamental forces? I mean when we apply force on something through contact, at the atomic level it is the electromagnetic repulsive force that causes the body to move isn't it. F=ma only applies for big bodies. But at extremely small distances such as the subatomic scale these things do not hold.
So to be saying that we apply a force to a body so that it moves one Planck length is meaningless. A Planck length is [tex]10^-^2^0[/tex] the size of a proton, which itself is [tex]10^-^4[/tex] the size of an atom. Plus the electrons are supposed to form an electron cloud and not a fixed orbit. Therefore atoms are always moving distances much larger than a Planck length.