# The Naked Scientists Forum

### Author Topic: Can the uncertainty principle be circumvented?  (Read 3606 times)

#### Supercryptid

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##### Can the uncertainty principle be circumvented?
« on: 04/03/2009 03:49:22 »
This may be a long shot, but here's a thought experiment to consider:

Quote
In the far distant future, a scientist decides that he will either measure the position or momentum of a particular subatomic particle in his laboratory to a high degree of accuracy. He decides that he will base his decision on which property to measure on the decay of a uranium atom. He puts the uranium atom in a box with a detector. He decides that, if the uranium atom decays within 10 seconds of him placing it within the box, he will measure the particle's position. If the uranium atom does not decay within 10 seconds of being placed within the box, he will measure the particle's momentum. He inserts the atom and waits for 10 seconds. It does not decay. Therefore, he measures the particle's momentum with an instrument to a high degree of accuracy.

Now, in this far distant future, it has been discovered that both traversable wormholes and parallel universes exist. In the scientist's laboratory, he has a wormhole-generating machine that can send information to and receive information from other universes. He decides that he will make a link between his universe (which we will call Universe A) and another universe which is almost exactly identical to his own (which we will call Universe B).

Universe A and Universe B are exactly the same, down to the subatomic level, except in one way. In Universe A, the uranium atom did not decay within 10 seconds. In Universe B, however, the uranium atom did decay. Therefore, the scientist in that universe (Scientist B) decided to measure the particle's position to a high degree of accuracy.

The original scientist (Scientist A) sends a message to Scientist B through the wormhole about the position of the particle. Since the two universes were identical in every way up until this point except in the uranium's decay or non-decay, the momentum of Universe's A particle should be exactly the same as that of Universe B's particle. Now Scientist B has both the particle's position and momentum measured.

Now there are many possible interpretations of this:

1) If the multiple-worlds theory is correct, and information can be sent to other universes, then the uncertainty principle may be circumvented.
2) Traversable wormholes can exist, but there are no parallel universe to visit.
3) Parallel universes exist, but traversable wormholes do not.
4) Neither traversable wormholes nor parallel universes exist.
5) Both traversable wormholes can exist and parallel universes exist, but no universe close enough in properties to our own exists for this thought experiment to be carried out.
6) Traversable wormholes can exist, and parallel universes like our own exist, but the particles in Universe A and Universe B are somehow "entangled" in such a way that measuring some property of one alters some property of the other, so that no useful information can be gained by the scientists' actions.
7) Traversable wormholes can exist, and parallel universes like our own exist, but there is no way that contact with a sufficiently similar universe can be made to perform the experiment.

What are your thoughts on this?

#### Vern

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##### Can the uncertainty principle be circumvented?
« Reply #1 on: 04/03/2009 05:51:47 »
I suspect that your option #4 is the most probable one. Neither multiple universes nor wormholes exist.

#### DoctorBeaver

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##### Can the uncertainty principle be circumvented?
« Reply #2 on: 04/03/2009 09:16:57 »
Quote
Universe A and Universe B are exactly the same, down to the subatomic level, except in one way. In Universe A, the uranium atom did not decay within 10 seconds.

That difference is more important than you may initially realise. It implies that the particles in universe B are totally separate entities from those in universe A. You are therefore, in effect, measuring 2 distinct particles rather than just 1. That means there is no way of guaranteeing that the particle in universe A has the same momentum & position as the particle in universe B.

In fact, that holds true for every particle in the universes. You would have to measure both values for every particle to know that there was no difference and the Uncertainty Principle would prevent you doing that.

There is, though, something that troubles me about the Uncertainty Principle. In accelerators particles are smashed together. The exact point of the collision is known as is the mass of the particles and their velocity. Surely, then, that means that both momentum & position are known.

I don't pretend for 1 moment to understand physics to any great extent so I've obviously got something wrong somewhere. There is no way a layman such as I could find a hole in 1 of the underlying principles of modern physics, so can someone please tell me where I'm going wrong?

#### lightarrow

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##### Can the uncertainty principle be circumvented?
« Reply #3 on: 04/03/2009 12:20:36 »
This may be a long shot, but here's a thought experiment to consider:

Quote
In the far distant future, a scientist decides that he will either measure the position or momentum of a particular subatomic particle in his laboratory to a high degree of accuracy. He decides that he will base his decision on which property to measure on the decay of a uranium atom. He puts the uranium atom in a box with a detector. He decides that, if the uranium atom decays within 10 seconds of him placing it within the box, he will measure the particle's position. If the uranium atom does not decay within 10 seconds of being placed within the box, he will measure the particle's momentum. He inserts the atom and waits for 10 seconds. It does not decay. Therefore, he measures the particle's momentum with an instrument to a high degree of accuracy.

Now, in this far distant future, it has been discovered that both traversable wormholes and parallel universes exist. In the scientist's laboratory, he has a wormhole-generating machine that can send information to and receive information from other universes. He decides that he will make a link between his universe (which we will call Universe A) and another universe which is almost exactly identical to his own (which we will call Universe B).

Universe A and Universe B are exactly the same, down to the subatomic level, except in one way. In Universe A, the uranium atom did not decay within 10 seconds. In Universe B, however, the uranium atom did decay. Therefore, the scientist in that universe (Scientist B) decided to measure the particle's position to a high degree of accuracy.

The original scientist (Scientist A) sends a message to Scientist B through the wormhole about the position of the particle. Since the two universes were identical in every way up until this point except in the uranium's decay or non-decay, the momentum of Universe's A particle should be exactly the same as that of Universe B's particle. Now Scientist B has both the particle's position and momentum measured.

Now there are many possible interpretations of this:

1) If the multiple-worlds theory is correct, and information can be sent to other universes, then the uncertainty principle may be circumvented.
2) Traversable wormholes can exist, but there are no parallel universe to visit.
3) Parallel universes exist, but traversable wormholes do not.
4) Neither traversable wormholes nor parallel universes exist.
5) Both traversable wormholes can exist and parallel universes exist, but no universe close enough in properties to our own exists for this thought experiment to be carried out.
6) Traversable wormholes can exist, and parallel universes like our own exist, but the particles in Universe A and Universe B are somehow "entangled" in such a way that measuring some property of one alters some property of the other, so that no useful information can be gained by the scientists' actions.
7) Traversable wormholes can exist, and parallel universes like our own exist, but there is no way that contact with a sufficiently similar universe can be made to perform the experiment.

What are your thoughts on this?

8)(≈ 7bis)The "distance" between the two universes A and B cannot be determined better than h/Δp
« Last Edit: 04/03/2009 12:22:10 by lightarrow »

#### lightarrow

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##### Can the uncertainty principle be circumvented?
« Reply #4 on: 04/03/2009 12:26:01 »
There is, though, something that troubles me about the Uncertainty Principle. In accelerators particles are smashed together. The exact point of the collision is known as is the mass of the particles and their velocity. Surely, then, that means that both momentum & position are known.
You know the point of collision and the energy-momentum of them with a limited precision (which is always less than what you could compute with the Indeterminacy Principle).

#### DoctorBeaver

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##### Can the uncertainty principle be circumvented?
« Reply #5 on: 04/03/2009 13:57:02 »
Why is the precision limited?

#### lightarrow

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##### Can the uncertainty principle be circumvented?
« Reply #6 on: 04/03/2009 15:02:13 »
Why is the precision limited?
Because the measuring instruments are not perfect.

#### DoctorBeaver

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##### Can the uncertainty principle be circumvented?
« Reply #7 on: 04/03/2009 15:14:19 »
Simple as that,eh! Thank you.

#### swansont

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##### Can the uncertainty principle be circumvented?
« Reply #8 on: 04/03/2009 15:17:04 »
Why is the precision limited?

Also because of the uncertainty principle.

Collisions have cross-sections.  The targeting is not so precise that they know the exact position.  They use the cross section and targeting to increase the probability of a collision, but they still rely on it being a stochastic process.

At the LHC: "So even though we squeeze our 100,000 million protons per bunch down to 64 microns (about the width of a human hair) at the interaction point. We get only around 20 collisions per crossing with nominal beam currents."

http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/collisions.htm

#### lightarrow

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##### Can the uncertainty principle be circumvented?
« Reply #9 on: 04/03/2009 15:19:59 »
Simple as that,eh! Thank you.
I remember discussing such a question with an experimental particle physicist, but I sincerely can't remember the details; I barely remember that the uncertainty of the Indetermination Principle is quite far to be reached by present experiments.

#### yor_on

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##### Can the uncertainty principle be circumvented?
« Reply #10 on: 05/03/2009 19:27:38 »
I'm getting boring here :)
The only thing I seem to write those days is Interesting::))
But that's what it is, interesting.

If I understand this right Swansont:)
You will have two beans crossing each others path?
Each beam containing around a 100,000 million protons?
And how compressed is each burst?

Or is that the total amount of particles meeting each other?
By "per bunch' I will presume to mean that they are sent in 'bursts'?

The diameter of each beam is around 64 microns which then should be 0,064 mm (0,000064 m.)
The diameter of a proton is about a Femtometer
(1 fm = 10^{-15} m = 0.000000000000001 m)

So is there any calculations done on how much of this that will represent 'space' in those collisions?

percentage, sort of :)
As there only is 20 collisions 'per beam crossing'?

Could one use this to measure a 'probability' - curve and perhaps get some 'measurement' of Heisenberg's uncertainty principle?
Or am I bicycling again, I know that HUP flatly states that "increasing the accuracy of measurement of one observable quantity increases the uncertainty with which another conjugate quantity may be know"
What I'm wondering though is if there would be a defined 'curve' for when you have a 'ideal' proportion of (?)variables(?) ( like proton density/time f.ex in that/those beams, and no, you're not allowed to kill the bearer:)

As a way to get more 'collisions' and of course, a probability curve for narrowing all parameters :::)))

« Last Edit: 05/03/2009 19:31:10 by yor_on »

#### The Naked Scientists Forum

##### Can the uncertainty principle be circumvented?
« Reply #10 on: 05/03/2009 19:27:38 »