Uncertainty principle at the macroscopic level

In summary, the conversation discusses the application of Heisenberg's uncertainty principle at the macroscopic level. It is suggested that increasing the Planck constant to a larger value would have minimal effects at this level. The concept of knowing both the velocity and momentum of a particle simultaneously is also debated, with the conclusion that the uncertainty principle still applies as the measurements would yield different results each time.
  • #1
preitiey
11
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what will be the scenario if Heisenberg's uncertainty principle is applied at macroscopic level?
 
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  • #2
That's kind of hard to do without really messing things up. Let's increase the Planck constant so that the Planck length increases from 1.6 10-35 meters to about a centimeter. The first problem I'm running into is trying to hit the correct key on my keyboard. They're only slightly further apart than the Planck length, so it's not clear that they're in different places. Also, it seems I can tell either where they are or how fast they're moving, but not both very accurately.
 
  • #3
Can we practically think of this dimension for Planck's constant? If yes, that means we are assuming the energy of quanta and its frequency of approximately same value and that too quite large. possible so?
 
  • #4
In view of the earlier posts, I am not sure what the original question meant. Are we talking about applying the same uncertainty principle (with the standard value for Planck's constant) to macroscopic phenomena around us, or are we talking about a mythical universe in which Planck's constant is huge?
 
  • #5
Yes, I am talking about applying this principle to macroscopic level, that means to a level where we can watch it significantly. Will this principle hold for macroscopic dimension?
 
  • #6
preitiey said:
Yes, I am talking about applying this principle to macroscopic level, that means to a level where we can watch it significantly. Will this principle hold for macroscopic dimension?
The HUP is not limited to any particular size, BUT ... for all practical purposes it is irrelevant at the macroscopic level. You could watch a macroscopic object for MUCH longer than the universe has already existed and you would never see any change.
 
  • #7
Here one thing I am confused with:
we know p = mv, v is the velocity of the particle.
if velocity is known, momentum can be calculated. But velocity is determined by the displacement of the particle within some time range. so for that time range, we know where the particle is. This means we know both momentum and position simultaneously. What's wrong here?
 
  • #8
preitiey said:
Here one thing I am confused with:
we know p = mv, v is the velocity of the particle.
if velocity is known, momentum can be calculated. But velocity is determined by the displacement of the particle within some time range. so for that time range, we know where the particle is. This means we know both momentum and position simultaneously. What's wrong here?
There has been some lively discussion here about whether the HUP applies to a single measurement or not. That is, some people argue that you can in fact know the velocity and momentum of a single particle at a single time. What is not in any dispute at all, however, is that you won't get the same answer twice in a row.

That is, if you could set up the EXACT same starting conditions on a quantum particle multiple times and each time measure the velocity and momentum of the particle you would get a different answer each time and the distribution of the answers would follow the HUP.

So "knowing" both the velocity and momentum of a quantum object really doesn't really tell you what you think it tells you.
 
  • #9
preitiey said:
what will be the scenario if Heisenberg's uncertainty principle is applied at macroscopic level?

The uncertainty is there, but it's too small to notice.
preitiey said:
Here one thing I am confused with:
we know p = mv, v is the velocity of the particle.
if velocity is known, momentum can be calculated. But velocity is determined by the displacement of the particle within some time range. so for that time range, we know where the particle is. This means we know both momentum and position simultaneously. What's wrong here?

In QM you have:

##<p> = m\frac{d<x>}{dt}##

This is a relation between expectation values of position and momentum. It's not a relation between specific measurements of position and momentum.
 
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Related to Uncertainty principle at the macroscopic level

1. What is the uncertainty principle at the macroscopic level?

The uncertainty principle at the macroscopic level, also known as the Heisenberg uncertainty principle, is a fundamental principle in quantum mechanics that states that it is impossible to know with certainty both the position and momentum of a particle at the same time.

2. How does the uncertainty principle apply to macroscopic objects?

The uncertainty principle applies to macroscopic objects in the sense that it sets a limit on our ability to measure their properties accurately. This means that even for objects that are large enough to be seen with the naked eye, there will always be a degree of uncertainty in our measurements of their position and momentum.

3. What is the significance of the uncertainty principle at the macroscopic level?

The uncertainty principle at the macroscopic level has significant implications for our understanding of the physical world. It challenges the classical view of determinism and suggests that there is inherent uncertainty in the behavior of particles at a fundamental level. It also has practical implications for precision measurements and technological applications.

4. Can the uncertainty principle be violated at the macroscopic level?

No, the uncertainty principle cannot be violated at the macroscopic level. It is a fundamental principle of quantum mechanics that has been extensively tested and has not been found to be violated. However, the effects of the uncertainty principle may not be noticeable for macroscopic objects due to their large size and mass.

5. How does the uncertainty principle relate to other principles of physics?

The uncertainty principle is closely related to other principles of physics, such as the principle of complementarity and the concept of wave-particle duality. It also has connections to other principles of thermodynamics and information theory. The uncertainty principle is a fundamental aspect of nature that is integral to our understanding of the physical world.

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