The biggest collection of brain-boggling brains ever assembled!

The 1927 Solvay conference on particle physics: back row, third from right, Werner Heisenberg, sixth from right, Erwin Schrödinger; middle row, from right, Niels Bohr, Max Born, Louis de Broglie and centre, Paul Dirac. Front row, second from left, Max Planck, next to him, Marie Curie, then Hendrik Lorentz and Albert Einstein. Of the 29 pictured, 18 won Nobel prizes, Curie in both physics and chemistry

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This picture and much of the basis for my post is taken from an article by Philip Ball at the Prospect site and he is definitely not to blame for my misinterpretations!

Crikey!  Even looking at that collection of mammoth 'brain-boxes' gives me a headache!  Well, what else do you expect from a man who failed Maths, Physics & Chemistry at school?  Even so, with the courage of the truly stupid I will attempt to provide you with the essence of Mr. Ball's essay which is worth reading in full - in fact it might be essential to do so because it is quite likely that I shall get hold of the wrong end of Schrödinger's cat!

Mr. Ball is taking a long view of quantum theory to see where and what it has lead to in the past 100-odd years. It all began with Max Planck who theorised that light was actually made up of tiny discrete bits of energy which he called 'photons'.  Einstein seized upon this and showed how it was that these high speed particles, or 'quanta', which knocked the electrons out of bits of metal, the process we know as the photo-electric effect.  And, as Mr. Ball usefully reminds us, it was for this paper that Einstein won his Nobel prize - not relativity.  Even so, from that time on, it was all downhill for physics, or perhaps, all upside down and inside out might be a better description.  But despite its almost 'unreal' description of 'reality', within the last 100-odd years quantum physics has solved innumerable problems and been turned to immense practical use in a variety of fields:

Scientists routinely adopt the approach memorably described by Cornell physicist David Mermin, as “shut up and calculate.” They use quantum mechanics to calculate everything from the strength of metal alloys to the shapes of molecules. Routine application of the theory underpins the miniaturisation of electronics, medical MRI imaging and the development of solar cells, to name just a few burgeoning technologies.

It is very necessary for physicists to keep 'shtum' and just stick to the maths because the whole field of quantum physics is based on paradox after paradox.  'Things' are and are not at the same time!  'Reality' is that these tiny particles might be here doing this, or over there doing that and you will not know until you 'look' at them at which point 'reality' or part of it, collapses, so it wan't very 'real' after all because merely by 'looking' you alter 'reality'!  Hence, Schrödinger's famous cat really is both alive and dead simultaneously until you open the box to check, at which point one set of possibilities collapses.  I could go on but the late, and very great, Richard Feynman put it better than anyone:

I think I can safely say that nobody understands quantum mechanics.(1)

And he won a Nobel prize on the subject!  Still, that is hardly surprising given the nature of that mysterious entity we call 'light'.  In the earliest science, light was considered to be made up of particles but then later investigation showed that it was probably more like a wave.  Then along came Planck and, hey-ho, we were back to particles again.  Once more, Feynman does his best to explain it:

This growing confusion was resolved in 1925 0r 1926 with the advent of the correct equations for quantum mechanics.  Now we know how the electrons and light behave.  But what can I call it?  If I say they behave like particles I give the wrong impression; also if I say they behave like waves.  They behave in their own inimitable way, which technically could be called a quantum mechanical way.  They behave in a way that is like nothing you have ever seen before. (1)

So, today they are both waves and particles at the same time!  However, even given this weird, paradoxical description of a totally different 'reality' below the level of the everyday 'reality' which we inhabit and experience, nevertheless, quantum physics is highly accurate as Mr. Ball reminds us:

Quantum mechanics is one of the most reliable theories in science: its prediction of how light interacts with matter is accurate to the eighth decimal place.

So that's alright, then!  Even so, the description of 'reality' offered by quantum physics, that nothing at the sub-atomic level is ever certain, only the odds on various outcomes are accurate, was hardly satisfactory:

But the question of how to interpret the theory—what it tells us about the physical universe—was never resolved by founders such as Niels Bohr, Werner Heisenberg and Erwin Schrödinger. Famously, Einstein himself was unhappy about how quantum theory leaves so much to chance: it pronounces only on the relative probabilities of how the world is arranged, not on how things fundamentally are. (My emphasis)

Back in the '20s, Neils Bohr and his 'disciple', Werner Heisenberg, attempted to come to terms with the paradoxical nature of the science they were investigating and proclaimed the Copenhagen Interpretation.  As Mr. Ball explains:

Most physicists accept something like Bohr and Heisenberg’s Copenhagen interpretation. This holds that there is no essential reality beyond the quantum description, nothing more fundamental and definite than probabilities. Bohr coined the notion of “complementarity” to express the need to relinquish the expectation of a deeper reality beneath the equations. If you measure a quantum object, you might find it in a particular state. But it makes no sense to ask if it was in that state before you looked. All that can be said is that it had a particular probability of being so. It’s not that you don’t “know,” but rather that the question has no physical meaning. Similarly, Heisenberg’s uncertainty principle is not a statement about the limits of what we can know about a quantum particle’s position, but places bounds on the whole concept of position.

In other words, they are saying that the quantum description of the world beneath the atomic level is it and all about it; nothing more to see, folks, just move along.  But there is one nagging doubt, one piece of the jigsaw which remains stubbornly innaccesible, and that is the proposed marriage between quantum mechanics and gravity.  So far,no one has succeeded in wedding these two aspects of 'reality' together and until they do, the description remains incomplete.

(1) Richard Feynman, The Character of Physical Law, ch.6

 

Comments

[dearieme]

There is a superb old paperback giving an account of the development of quantum mechanics that will appeal to the intelligent schoolboy - and perhaps you, Duffers. "The Strange Story of the Quantum" by Banesh Hoffman. Wonderful name, wonderful book.

P.S. That assemblage in the photo was the finest collection of physicists ever gathered since Sir Isaac drank his last, lonely cocoa before bed.

[David Duff]

"intelligent schoolboy"? My teachers never thought so! I will look out for that book, thanks, DM.

[Andra]

Well, I can cheerfully say that I don't understand it either.
When can I pick up my Nobel prize (and the cheque)?

[Whyaxye]

"Of the 29 pictured, 18 won Nobel prizes, Curie in both physics and chemistry"

Even at these stratospheric levels, it appears that women can multi-task whereas men cannot.

[David Duff]

Andra, as we used to say in the second-hand car trade 'the cheque's in the post - honest!'!

Well spotted, W, but somehow the phrase 'multi-tasking' at that level seems so mundane.

[Andra]

Lovely. When I receive the cheque I'll take you and the missus to lunch at La Lucciola in Bali.
It's lovely to sit and watch the sunset over the sea, with a Bintang or two.
The sun sets in the west there, you know.

[David Duff]

But ... but ... it can't, 'cos you're in the east and as 'seen' from here your sun sets in the east. I'm sure that what old Albert taught me! It's relative, innit?