Tuesday, July 14, 2009

Doubt in Heisenberg's Uncertainity Principle

According to Heisenberg's Uncertainity Principle , the exact position and momentum of a moving body cannot be determined to a value of infinite precision .
Now my question is that if a body is at rest , which means it has no momentum at all , then can we determine the exact position of the body , means does this principle applies to the bodies at rest . If no , then we can determine the exact position of a body at rest . Now we can choose a suitable frame of reference with respect to which the body is at rest , and by doing that we can determine the exact position of the body , and if we know the velocity of the frame of reference in which we are sitting with respect to another then we can also determine the exact momentum of the body at the same instant of time . Isn't it contradictory to this principle ? Means how does Heisenberg's Uncertainity Principle applies when we are observing the position and momentum from different frames .


Doubt Clearer1:
No body can be at rest, due to the uncertainty principle. There is always some uncertainty in it's position and momentum. This is also the reason why we cannot reach absolute zero, as a matter of principle.

Doubt Clearer2:
In macroscopic world we feel that some things are stationary just because their motion is so feeble to be detected by our eye. Actually its not in rest.

Doubt Clearer3:
Now my question is that if a body is at rest , which means it has no momentum at all

According to initial papers on quantum theory by Planck, he said, "the minimum physical action that occurs in Nature is ħ/2". A minimum physical action means that there is no rest in Nature, however small motion may be. Planck puts it like: "Natura facit saltus" that means "Nature makes jumps".

Doubt Clearer4:
Nothing can be at absolute rest. There is something called zero point energy given by half of hbar. At finite temperatures there is always some thermal motion. Even at absolute zero (if it can ever be achieved) a body will have zero point motion.

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