Bill

If you could prove that assertion to the satisfaction of the scientific community, the Nobel Prize for Physics could be yours sometime in the not very distant future.

I was long under the impression (as you seem to be) that the "uncertainty" in the "Heisenberg Uncertainty Principle" was cuased by the act of measuring either the position or the momentum. However, several years worth of additional casual reading on matters of quantum mechanics has convinced me that beausoleil has rather the better position in the debate between you too and that the "uncertainty" is a matter of the nature of reality because (at least at the present) we are dealing with a probability field rather than a nice simple sub-atomic particle (which is how we thought about these matters traditionally; I still remember using ping-pong balls for protons and neutrons and beads for electrons in creating atomic models in school).

One of the inputs to the probability calculation is the uncertainty as to whether or not we are dealing with a wave or a particle. Anybody who knows quantum mechanics knows that we can get either effect out of any given photon. When a photon strikes an electron, you get a temporary increase in the energy content of the electron (it jumps out a shell), but then it re-emits the photon and falls back in a shell. Is this reaction of the electron due to an increase in mass (matter) or energy? Why?

Everybody working in particle physics ought to know just how ignorant we are of basic scientific facts these days. But of course, we are not so ignorant as to believe that Heiesenberg will be shown to be wrong any time soon.....

== Bill

Mark_Chid

A point I once read, which makes a great deal of sense, is that the reason that Quantum Theory seems so bizarre is that we are used to thinking in metaphors when we do science and that when we get down to electrons and protons and quarks the metaphors break down. Electrons behave like electrons - thats all. they are not 'particles' or 'waves' they are electrons. They are so basic that we can't refer to them in terms of anything else, and tehrefore we can hardly talk about them at all.

Just like light. Light is not a wave OR a particle, its light, which is something else altogether!

Mark_Chid

Actually theres a very elegant explanation of the double slit effect that assumes the many-worlds interpretation rather than the classical probabalistic one is the true picture of Quantum Mechanics. It convinced me that Many Worlds was true because it actually EXPLAINS the effect rather than simply renaming the problem!

Its discussed in the appendices of Michael Chrichton's book 'Timeline'.

Answerer

To me, MWI is nothing but another science fiction story. To think that the multiverse actually possessed a permanent memory storage system is even more bizarre than the randomness behaviour of an electron.
MWI also violated the law of conservation of mass-energy. Just imagine that there are infinite number of universes instantly popped out of nowhere every planck time, which is equivalent to the assumption that infinite amount of energy is being created here and then.
Anyway, I would rather put more faith in superstring theory or quantum loop theory that sounds more rational than any other bizarre quantum interpretations.

echidna

The thought of Mother Theresa married to GWB always ruled out the MWI for myself, and even that’s far from being the least likely universe …

exactamundo

The physical laws of the universe are governed by the interaction of the smallest particles of matter in the universe, which were once thought to be atoms. Mathematics has now shown that there seems to be smaller particles of matter effecting the interaction of the atoms, These particles are called quarks which are inside atoms. The physical laws of the universe are only observations of how one atom reacts to another atom which reacts to another atom and so on and so on which then defines the physical laws of our universe.

The physical laws of the universe are not created but discovered through observation and mathematics is used to predict and explain the observation.

Some laws of physics are being refined because of the newly discovered quark's characteristics.

Even though atom's characteristics were predicable most of the time sometimes they acted a little bit differently under different situations and jived with the previous mathematical models.

So just like how science discovered the tenth planet "Pluto" by observing that the other planet's behaviors were not acting as predicted and that there must be something else effecting their behavior, Pluto was discovered, with observation and mathematics, just like the quarks have now been discovered.

Science is always testing and re-testing ideas and hypothesis to keep them real and true. When more information is discovered that might prove an hypothesis wrong or cause it to be refined, then this is a good thing because it keep science real and true, unlike biblical truths that require incredible acts of faith, without observation to keep the "bible's truths" real.

Jesse

Answerer:
To me, MWI is nothing but another science fiction story. To think that the multiverse actually possessed a permanent memory storage system is even more bizarre than the randomness behaviour of an electron.

"Posessed a permanent memory storage system?" What are you referring to here?

Answerer:
MWI also violated the law of conservation of mass-energy. Just imagine that there are infinite number of universes instantly popped out of nowhere every planck time, which is equivalent to the assumption that infinite amount of energy is being created here and then.

This is an incorrect description of the MWI. The MWI does not postulate new universes popping out of nowhere--it just postulates a single universal wavefunction which evolves according to the deterministic Schrodinger equation, without any mysterious "random collapse" due to "measurements." In a way this makes it the simplest of all interpretations, at least in terms of requiring the fewest assumptions beyond the actual equations of quantum mechanics.

Also see <a href="http://www.hedweb.com/everett/everett.htm#conservation" target="_blank">Does many-worlds violate conservation of energy?</a> from <a href="http://www.hedweb.com/everett/everett.htm" target="_blank">The Everett FAQ</a>.

Answerer:
Anyway, I would rather put more faith in superstring theory or quantum loop theory that sounds more rational than any other bizarre quantum interpretations.

You're comparing apples and oranges. Superstring theory and quantum loop theory are theories of quantum gravity, and just like quantum field theory they would presumably be compatible with any interpretation of QM.

[ September 06, 2002: Message edited by: Jesse ]</p>

Answerer

I'm refering to one of the assumptions made in MWI which has something to do with the past alternative universes.

Sorry, it isn't the simplest interpretation at all, in fact, its one of the hard ones. Furthermore, that universal wave function you are talking about do require the existence of other 'alternative' universes, so where do those
universes come from?


Not really, since quantum gravity is the ultimate combination of quantum mechanics and general relativity. Therefore, how is string theory 'restricted' from giving new quantum interpretations?

Jesse

Jesse:
"Posessed a permanent memory storage system?" What are you referring to here?

Answerer:
I'm refering to one of the assumptions made in MWI which has something to do with the past alternative universes.

I still don't understand what you're talking about, could you elaborate?

Jesse:
This is an incorrect description of the MWI. The MWI does not postulate new universes popping out of nowhere--it just postulates a single universal wavefunction which evolves according to the deterministic Schrodinger equation, without any mysterious "random collapse" due to "measurements." In a way this makes it the simplest of all interpretations, at least in terms of requiring the fewest assumptions beyond the actual equations of quantum mechanics.

Answerer:
Sorry, it isn't the simplest interpretation at all, in fact, its one of the hard ones.

It's the simplest in terms of its theoretical assumptions. Other interpretations of QM need to postulate two separate things--first the equations for the deterministic evolution of the wavefunction when a system is not being observed, and second, a "collapse" of the wavefunction when it is measured, with the probability of different states being proportional to the square of the amplitude. The MWI says, no, the evolving wavefunction is all there is.

Answerer:
Furthermore, that universal wave function you are talking about do require the existence of other 'alternative' universes, so where do those
universes come from?

The universal wavefunction is no different than any other wavefunction. If I calculate the evolution of the wavefunction for an electron over some period of time, it can be shown mathematically that this is equivalent to computing a weighted sum of all possible paths (or 'histories') the electron could have taken (this is the <a href="http://www.maths.usyd.edu.au:8000/u/hughl/PI.html" target="_blank">Feynman path integral</a>). Where do those "alternate histories" of the electron come from? I guess one answer would be that they're implicitly contained in the rules for the evolution of the wavefunction, and the same would be true for the wavefunction of the whole universe.

Jesse:
You're comparing apples and oranges. Superstring theory and quantum loop theory are theories of quantum gravity, and just like quantum field theory they would presumably be compatible with any interpretation of QM.

Answerer:
Not really, since quantum gravity is the ultimate combination of quantum mechanics and general relativity. Therefore, how is string theory 'restricted' from giving new quantum interpretations?

If string theory keeps the same basic elements of quantum mechanics in other quantum theories (basically, treating the dynamics of any system in terms of a wavefunction with complex amplitudes) then it will not say anything new about the interpretation of quantum mechanics. String theory in its current form does not modify this basic framework, as far as I know. But you're right, a theory of quantum gravity could shake things up--just as the idea of "spacetime" might not turn out to be basic but just derived from some more fundamental level, the same could be true of wavefunctions in QM. But as I said, I'm pretty sure that string theory still takes the wavefunction for granted, as does loop quantum gravity.

[ September 07, 2002: Message edited by: Jesse ]</p>

Answerer

Okay, allow me to ask another question, do those 'alternate histories' of the electrons fade away in time or do they remain unchanged permanently?