Quantum Physics

In another thread I was prodded to produce a Petty style exposition of Quantum Theory. Here's the opening salvo.

Prologue

The leading lights of physics were remarkably smug around the year 1900. They had good reason to be: 50 years earlier heat and temperature became unified with the same laws of motion that had been grandly predicting the movements of everything on earth and in the heavens for the past 200 years. 40 years earlier the Scotshobbit James Clerk Maxwell had pulled together disparate observations of electricity and magnetism, creating a unification that out of the blue explained where light and radio waves came from. 20 years earlier the concepts of statistical mechanics developed by Gibbs and Boltzmann were laying bare the detailed behavior of gasses and chemical reactions, even though the practitioners had no firm proof molecules even existed.

All these achievements were evolutionary rather than revolutionary: nobody had to unlearn old habits of thought to apply the new discoveries, simply learn new skills. So it was that in 1894 Albert Michelson declared that the future of physics lay in measurement to the 6th decimal point, and Lord Kelvin (one of the masterminds who united motion and heat) declared in 1900 that there was nothing new to be discovered in physics, echoing the need for more precise measurement. It should be pointed out that they were talking about far-reaching laws, not details like new elements. It was like saying that even though there were new lands and oceans to explore, the earth would continue to be round, and the sun would still rise like clockwork.

But they were deliberately ignoring the burning fuses of evidence everyone was aware of, deeming them details of small consequence. As early as 1850 the spectra of the elements were known to be more akin to barcodes than rainbows, and this fact was being used to identify elements (and identify helium in the sun before it was discovered on earth). But the current physics could explain discrete wavelengths by fixed oscillators: merely some details to be worked out in the structure of the elements; a spark, not a fire. The shape of the thermal radiation spectrum and the heat capacity of metals could not be explained; but this was also tied to hidden structure of the elements. Small sparks rather than a conflagration. But the sparks you ignore may be the sparkling fuses of bombs, and the brash new generation of physicists whose task it was to wrestle with these small problems ended up proving that the world was neither round nor flat, but topsy-turvy.

2 years after Michelson's statement, he made very careful measurements that showed light always traveled the same speed no matter what direction or speed the earth is moving, and a young Albert Einstein was prodded along the path that led to relativity. A year after Lord Kelvin declared there were no new discoveries, Max Planck explained thermal radiation by assuming energy was quantized rather than continuous. The paper made no stir (it was more a curve fitting technique than a bold new theory), but two years later Einstein repurposed the quantum concept to prove the existence of photons (impossible constructions under Maxwell's theory of light), and it was as if a sledge hammer hit the world of classical physics. That same year he also published Relativity, and the world was demolished.

The twin pillars of 20th century physics, quantum theory and relativity, are notable because they violate our intuition. I plan to provide a guided tour through the basic concepts of quantum theory, moving slowly and keeping the concepts as unmathematical as I can. I'll tackle roughly one topic per week:

1. Waves and superposition: quantum mechanics is often called wave mechanics, and before we get to the weird parts, we have to understand how waves in the everyday world behave. Dry but crucial.

2. History of the development of Quantum Theory: I gave some vague hints above, but will fill it out so that it makes sense.

3. Applying Quantum Theory: this is where the basic tools and predictions of quantum theory (not already described in the history section) are laid out.

4. Quantum Mechanics and Everyday Experience: in case the strangeness of QM is not apparent by now, it will here be related to the world we know.

See you here next weekend.

halfwise wrote:
2 years after Michelson's statement, he made very careful measurements that showed light always traveled the same speed no matter what direction or speed the earth is moving, and a young Albert Einstein was prodded along the path that led to relativity.

Nicely written! I look forward to future installments.

I can't resist one quibble though. Are you familiar with Dayton Miller's critique of the Michelson-Morley experiment and his further research? This article makes an interesting case, even if you choose not to accept it's conclusions:

http://www.orgonelab.org/miller.htm

That does seem to be a very valid and important experiment, and I don't doubt it was largely ignored due to bias towards relativity. But the reasons for this 'bias' were (and continues to be) overwhelming evidence that relativity works. I think the author of this review article damages his case in continuing to refer to this as an 'ether drift' experiment. Note that this phrase starts by assuming an ether, then assumes it is largely not observed because it is being dragged along with the earth, and the experiment observes slight discrepancies from being dragged along perfectly with the earth. This would mean out in space the effect would be huge, which contradicts mountains of observations of relativity at work on the astronomical scale.

If modern physics would go back and take this experiment seriously (and I think they should) they would probably relate it to dark matter, which has been shown to cluster around galaxies. This makes much more sense than assuming a cosmological ether that is being imperfectly dragged along with the earth. I have had doubts about ascribing dark matter to exotic particles that have otherwise been undetected in earthbound experiments, and have felt that observations of distant galaxies are subject to errors. But since I'm not an observational astronomer, I'm not qualified to critique their methods. The Miller experiment may be the only earthbound experiment to indicate the existence of dark matter, if only it were resurrected and brought to the attention of the modern generation of astrophysicists.

Actually Dave, Miller's work has not been ignored. An extremely detailed analysis of Miller's work was published online in 2008, going far beyond Shankland's critique. End result: Miller's positive results were statistically indistinguishable from zero.

http://arxiv.org/pdf/physics/0608238.pdf

Don't know if it made it in a peer-reviewed journal, there's a possibility nobody was interested in an examination of the flaws of a long disregarded experiment.

I expect that Dark Matter will turn out to be so out of our experience or capacity to understand that it never becomes observable in earth bound experiments. Maybe it is just Nothing but Nothing with strange powers, so how can you observe Nothing?

Thanks for this thread Halfwise its fab.

The early 20th century physicists had learned their lesson about the limits of human reasoning so well that by 1945 Richard Feynman's dissertation work (he would later revolutionize quantum mechanics) was dismissed with the phrase "Your idea is crazy, but not crazy enough to be true."

So glad you are undertaking this Halfwise- good opening and already keen for more.
I personally will be particularly interested when you eventually get to macro and micro- how all the weirdness down there makes all the regular stuff at our level, mainly because my own interest in quantum was sparked coming at it from the other side, from the shaman/mystic side and discovering rather suprisingly many of the underlying concepts seem remarkably similar.
Carry on the good work!

I want to know about Spooky Action at a Distance.

I can demonstrate that with nothing more than a gust of wind and my kilt at just the right angle.

Not sure I can compete with Petty's version, but I will cover SAAAD. Unfortunately it's only really spooky if you buy into the logical arguments behind it. Most books for the general audience simply tell you what the interpretation is without convincing you why you should believe it, in my opinion. Not too sure how much better I can do but will try.

So Religion and Science were twins separated at birth!

halfwise wrote:Actually Dave, Miller's work has not been ignored. An extremely detailed analysis of Miller's work was published online in 2008, going far beyond Shankland's critique. End result: Miller's positive results were statistically indistinguishable from zero.

http://arxiv.org/pdf/physics/0608238.pdf

Don't know if it made it in a peer-reviewed journal, there's a possibility nobody was interested in an examination of the flaws of a long disregarded experiment.

Very interesting. Thank you!

I'll confess I only made it through the introduction, conclusions and appendices, and about half the text. It's a little dense reading for a humble farmer.
{I'm personally much more comfortable with models that can be described in terms of fruits and vegetables. }

I lost confidence in your scientific viewpoint (and practical skills) when I saw plenty of carrots but no spaceship, Cap'n Dave - and not one hired carrot-skinner in sight!

David H wrote:
I'll confess I only made it through the introduction, conclusions and appendices, and about half the text. It's a little dense reading for a humble farmer.
{I'm personally much more comfortable with models that can be described in terms of fruits and vegetables. }

What, you think I read the damn thing?

I read the article you sent, but this second more modern one may fall under the category of proof by intimidation. Just don't have time for this kind of thing right now.