Science's Big Query: What Can We Know, and What Can't We?

The Wall Street Journal ^ | Friday, May 30, 2003 | SHARON BEGLEY

[Physicist]

First: The application of the Heisenberg's uncertainty principle to the question of what can or cannot be known is absurd. As if the "position" and "momentum," if any actual particle could actually be identified, and either its position or momentum measured? The entirety of the uncertaintly principle is not an indication of what cannot be known, but an observation about the statistical nature of what can be known, and a failure of the statistical method to resolve certain aspects of sub-atomic behavior. (The fact that another method might produce different results seems beyond the imagination of the current crop of so-called scientists.)

Sorry, but that's wrong. The HUP is not a limitation on measurement, it is a limitation on reality. If you measure the position of a particle to a very high degree of accuracy, it is not simply a matter of being unable to know what the particle's momentum is. After you make the position measurement, the particle does not have a specific momentum. It becomes physically spread out in momentum-space.

Likewise, the better we measure a particle's momentum, the more the wavefunction becomes physically spread out in space. This is not a "mathematical fiction"; the ensemble of trajectories represented by that distribution all physically contribute to the motion of the particle. The fact that individual electrons diffract through two spatially separated slits demonstrates that this is physics, and not philosophy.

[Physicist]

By the way, there are not multiple universes, or existences, or realities, either, anymore than there are multiple personalities.

Recommended reading: "Parallel Universes" by Max Tegmark, the cover article in the May issue of Scientific American. Max is (in my opinion) one of the two most brilliant professors in the physics department here at Penn, and a hell of a nice guy.

[Precis: "Not just a staple of science fiction, other universes are a direct implication of cosmological observations".]

Belief in either are similar pathologies.

The universe is the way that it is, and not how we would wish it to be.

[BSunday]

What we can know
Death is coming for each of us.
Liberals will always whine.
Supply side economics works
(Feel free to add your own, I'm too lazy...

What We Can't Know
Where Jimmy Hoffa's body is
Who else shot Kennedy
Where is D.B Cooper?
Again, feel free to add your own....

[Physicist]

Here it is: Parallel Universes by Max Tegmark

[Alamo-Girl]

What a superb article, Physicist! Thank you so much for the heads up!

I’m a big Tegmark fan – and because the subjects discussed in the article coincide a standing conversation with tortoise, predestination v free will, I’m giving him a heads up as well.

Of all the levels, the Level IV rings most true to me.

A common feature of all four multiverse levels is that the simplest and arguably most elegant theory involves parallel universes by default. To deny the existence of those universes, one needs to complicate the theory by adding experimentally unsupported processes and ad hoc postulates: finite space, wave function collapse and ontological asymmetry. Our judgment therefore comes down to which we find more wasteful and inelegant: many worlds or many words. Perhaps we will gradually get used to the weird ways of our cosmos and find its strangeness to be part of its charm.

Thanks again!

[Billthedrill]

Actually the theorem is not about "in practice" but "in principle"...

ARGH! You are, of course, correct, and that was even the point I was trying to make. English Language 1, BtD 0. Again.

It all devolves to the statement which many of us find threatening and all of us encounter at some point - that our comfortable, reassuring mental model is inadequate, and we have to change it. Writ large this is what Kuhn meant by "paradigm shift" but it is much more often encountered in mental activity at a much smaller scale than a paradigm. For example, while I understood it technically it took me a long time to shake it conceptually that an electron isn't a little bitty round thingy orbiting the nucleus like a moon around a planet. A lot of freshman philosophy papers go up in flames at that point.

[Hank Kerchief]

I said: By the way, there are not multiple universes, or existences, or realities, either, anymore than there are multiple personalities.

You said: How do you know that?

Thank you, thank you, thank you. This is the last argument of all those who propose something is true on the basis of ???? (imagination, hallucination, superstition), but without any evidence whatsoever. How do you know there is not a Phoenix? Can you prove Santa Claus does not exist somewhere? etc. etc. etc.

There is no end of things people can imagine and then invent arguments for the existence of. First, let me see some evidence, some reason for supposing there is the imagined other world, or reality, or "parallel" existence, then we can consider the question. In the mean time, there is as much reason to believe in the Phoenix or a leprechaun as in other "realities."

[tictoc]

Scientists are minions paid off by Lizard/human hybrids incubating in vast facilities underground. Their sole mission is to draw blinds over our eyes.

Fools! Do you think the lizard kings will spare you after the Emergence? No. Useful idiots. Also, I am drilling a hole in my backyard. Why wait for the Lizards to creep up on me.

I found this great clearing house of suppressed information on the Web, now I know all about you people. Confusing us with irrational (the word is a dead giveaway) numbers, teaching submission to "primes". The Founding Fathers would have given you an earful. We must return to wholesome integers.

[tortoise]

Tegmark is alright in my book, and is an insightful and clueful individual.

I've been involved in some interesting discussions lately regarding the usual QM oddities with some conclusions that might interest you. While still somewhat speculative, there is a solid model developing of aspects such as Heisenberg uncertainty, collapsing wave functions, and similar complexities that shows that these can all be expressed in a really tidy (if unusual) finite state system. If this holds up, it could unify the "weirdness" of QM with everything else in a single computational information theoretic framework.

I had hoped (and to a certain extent assumed) that something like this would happen eventually, but I wasn't counting on it because it looked difficult. It seems that there may very well be hope for this, though it is still way too early to say anything for sure. Consider this heads up on an interesting but speculative bleeding edge development. :-)

[Alamo-Girl]

Jeepers, tortoise!

That's exactly the kind of research that mesmerizes me and why I'm so "into" quantum field theory, STM and anything Penrose I can find.

I'm craving to know more already. Please, oh, please let me know as soon as there is anything in writing I can ponder!

[SunkenCiv]

A Blast from the Past.

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