B What about if I apply HUP to myself?

[dyn]

Hi
HUP states that if i know the exact position of a particle there must be infinite uncertainty in its momentum. What about if i apply HUP to myself ? Is it not possible for me to know that i am standing at a specified position and not moving ; implying zero uncertainty in both position and momentum ?
Thanks

 

[phinds]

First of all, the HUP is not applicable in any practical sense to macro objects but rather only to quantum objects. Second, it is not helpful to talk about single measurements. The real value of the HUP in distinguishing classical physics from quantum physics is this:

In classical physics, if you can set up an experiment EXACTLY the same every time then the results will be the same every time. In quantum physics, if you set up an experiment EXACTLY the same every time, the results will NOT be the same every time but will in fact have a statistical distribution described by the HUP.

 

[PeterDonis]

Is it not possible for me to know that i am standing at a specified position and not moving ; implying zero uncertainty in both position and momentum ?

No. But your mass is so large that you can have extremely small uncertainty in both your position and your velocity (which is how you actually judge how fast you are moving) while still not violating the HUP. In fact, in a practical sense there are other sources of uncertainty in your measurements that are far larger than the uncertainties imposed by the HUP, which is why, as @phinds says, the HUP is useless in a practical sense for macroscopic objects.

 

[Nugatory]

Hi
HUP states that if i know the exact position of a particle there must be infinite uncertainty in its momentum. What about if i apply HUP to myself ? Is it not possible for me to know that i am standing at a specified position and not moving ; implying zero uncertainty in both position and momentum ?
Thanks

You are not a particle, you are a collection of about $10^{27}$ particles. Each one of those particles has some uncertainty as to position and momentum, as required by the uncertainty principle.

It’s worth taking a moment to calculate the actual numerical values of the uncertainty in the position and moment of an electron confined within the volume of a water molecule. You’ll see how you can evade the uncertainty principle and you’ll feel a lot better about being made of uncertain particles.

 

[dyn]

You are not a particle, you are a collection of about $10^{27}$ particles. Each one of those particles has some uncertainty as to position and momentum, as required by the uncertainty principle.

That argument wouldn't apply if the mass of approx. 100kg consisted of a single particle

 

[StevieTNZ]

HUP states that if i know the exact position of a particle

then you say "apply HUP to myself"

Are you a particle?

 

[Nugatory]

That argument wouldn't apply if the mass of approx. 100kg consisted of a single particle

Yes, and in that case we would apply PeterDonis’s answer in post #3.

it’s still worth taking a moment to do the calculation and get some actual numeric values out. Say your hypothetical 100kg particle is prepared in a quantum state such that the uncertainty in its position is about one atomic diameter.…. What is the uncertainty in its momentum and hence its speed?

 

[Vanadium 50]

It sounds like you aren't asking a question so much as making an argument.

The first thng you should do is plug some numbers in. Keep in mind you can shift your weight and move around a bit. Do you know your position to a centimeter? A millimeter? A micron? A nanometer? Same with momentum./

Now multiply those numbers together. Did you violate the HUP?

 

[PeroK]

A street performer at Covent Garden violates the HUP, and several other laws of physics:

 

[Ibix]

We did this at school. Rolled a cricket ball through a doorway and worked out the possible velocity uncertainty. Unfortunately a fly sneezed on the other side of the world and the shockwaves ruined our data collection.

 

[votingmachine]

Hi
HUP states that if i know the exact position of a particle there must be infinite uncertainty in its momentum. What about if i apply HUP to myself ? Is it not possible for me to know that i am standing at a specified position and not moving ; implying zero uncertainty in both position and momentum ?
Thanks

You need to figure out exactly how you are going to perform these measurements that assert a perfect measurement of zero velocity and perfect placement in position. What you will find is that there is no way to make the exact measurements you claim.

It is indeed not possible for you to know that you are standing at a specified position and not moving beyond the limit of the HUP.