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Re: [Phys-L] Quantum Biology



On 10/09/2015 10:40 AM, Savinainen Antti wrote:

<https://www.ted.com/talks/jim_al_khalili_how_quantum_biology_might_explain_life_s_biggest_questions/transcript?language=en>

It seems that Schrödinger's vision on life & physics is finally
coming true. This at least what All-Khalili seems to be saying: "in
the last 10 years, there have been experiments emerging, showing
where some of these certain phenomena in biology do seem to require
quantum mechanics".

I'm not impressed. The part that is real is not surprising, and
the part that is surprising is not real. It's pure speculation.

Here's how I see it: Quantum mechanics has some weird aspects,
but overall it's not nearly as weird as some people claim it is.

a) For starters, 99% of the time, quantum mechanics predicts
that the classical approximation is valid. This is as it
should be. QM knows when classical physics is correct.
BTW the reverse is not true; classical physics knows almost
nothing of QM.

b) In 99% of the remaining cases, QM makes predictions that
are non-classical but obviously correct and non-weird. For
example, classical physics unequivocally predicts that atoms
have zero size, whereas QM predicts that they have a size on
the order of a Bohr radius, i.e. something that scales like ℏ.

So something like 99.99% of the total predictions are non-weird.
This is stuff that can be understood in terms of high-school
wave mechanics (ripple tanks etc.) if you think about it the
right way.

If you want to talk about quantum biology, start with the
fact that biology requires non-zero-sized atoms. This is
quantum-mechanical, biological, not weird, and not new.

c1) Now we come to exchange of identical particles. You can
introduce the /outline/ of this idea a the high-school level,
and use the Pauli exclusion principle as an example. However,
if you pursue it, the right answer soon becomes quite complicated.

The exclusion principle has a big effect on atomic physics and
chemistry; without it, all the elements would just act like
isotopes of hydrogen. However, the typical biologist doesn't
need to worry about this. The easiest approach is to accept
the periodic table as a given, empirically-established fact.

Whether you consider this "weird" or not is a matter of opinion.
If you look at all closely at the periodic table you find plenty
of complexity, but most people just accept it. In any case,
there's nothing the least bit new about it.

Next, consider the fact that you could not possibly explain
the acidity of acetic acid without quantum mechanics. This
is certainly quantum-mechanical, certainly biological, and
certainly not new.

Next, consider the fact that you could not possibly explain
aromatic molecules without quantum mechanics. This category
includes four of the amino acids and all five of the nucleotides.
This is certainly quantum-mechanical, certainly biological,
and certainly not new.

Similarly, you could not possibly explain the magnetism of
matter (and ferromagnetism in particular) without quantum
mechanics. This is relevant to one of the N ways that
migratory species find their way. This is well known to
every solid-state physicist on earth. To suggest that
there is something mystical about it strikes me as kooky.

c2) Exchange also leads to superfluidity (which includes
superconductivity). This is starting to get weird. We
are talking about quantum coherence on a macroscopic scale.

Nobody predicted this. Indeed it took decades to come up
with a reasonable explanation, even after the phenomenon
was observed experimentally. The explanation requires a
lot more than high-school ripple-tank physics.

d) The truly weird part of QM has to do with Schrödinger cat
states and Bell inequalities. I'm not sure anybody fully
understands this stuff. Einstein assumed that there "had to
be" an explanation in terms of hidden variables, and famously
said God does not play dice. However, the equations and the
experiments say Einstein was completely wrong. No hidden-
variable theory could possibly give the right answers.

On the other hand, IMHO the chance that "spooky action at a
distance" has any relevance to biology is exceedingly slim.
For one thing, the biological system has nothing to gain by
it; you can't do useful work with it, and you can't transfer
information with it.

James Randi said "Extraordinary claims require extraordinary
proof". Mystical speculation doesn't cut it.