Saturday, March 28, 2009

Now You See It Now You Don’t

Some information here from the Economist March 7th - the remainder from my now 28 year old Ph.D studies and pondering.

A slightly obscure realm of physics is concerned with what seems to be as much a question of philosophy as of physics - the issue of the interaction between matter and anti matter.
Physicist Lucien Hardy asserted that when a particle meets its anti particle the pair explode in a burst of energy leaving nothing. His formulation did however leave open the possibility that the particles might collide and survive if they were unseen.

What nonsense is this? The "seen unseen" issue arises from the work of Bohr and Heisenburg in the 1920s showing that the very act of observing altered what was being observed and thus whatever "was" before it was seen could never be observed. More practically the act of observing plus all the apparatus being used to observe alters what is being observed - that apparatus includes the theories brought to the "seeing".

This then - starts to look a bit more exciting and relevant. If the thought apparatus brought to the observation process is in fact defining in some (unspecified) part what is being observed then we ought to be careful what we think.

The Economist reports however that two independent groups of physicists have demonstrated that things do indeed "exist" even when not seen (bad luck for the question "is a man wrong even when he says something in a dark wood and no woman can hear him"- at least for males).

The two teams - one from Japan and one from Canada - probed "reality" without disturbing it by using what is, in effect, an analogue model. Polarisation of photons (which are the particles making up light) involves behaviour which follows exactly the behaviour of the particles in Hardy's paradox.

The trick was to NOT gather all the information (shades of the non barking dog in the Sign of Four - again) in any one experiment and thus not "observe" in any one experiment. Data were then pooled so that the sum of the partial information allowed confirmation of collision and survival but only when not seen.

What might this mean for us lesser mortals trying to explain and describe social, economic and cultural behaviour. Well it admits the possibility, may even prove, that such phenomena exist but - the catch is they cannot be observed without altering them. So objectivity is both possible and impossible all at the same time.

The claim that objectivity is not possible is far from new but has been made before primarily as a matter of assertion and disciplinary defensiveness. These results suggest a more robust explanation is possible - and yes, theory and one's epistemological apparatus matter very, very much.

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