Wednesday, December 29, 2010

In The Beginning...

This is not a bad article, written by Martin Rees. But then again, I'm a bit disappointed at how sloppy it is in some areas. I'm fully aware that this was written for the general audience, and it appeared in a regular newspaper. But still, he could have made it a bit more accurate without changing the readability of the article.

For example, he wrote this about a possible extra dimension for gravity:

Some have speculated that other universes could exist in tandem with ours. Imagine ants crawling around on a large sheet of paper (their two-dimensional universe). They would be unaware of a similar sheet that is parallel to it. Likewise, there could be another entire universe (with three-dimensional space, like ours) less than a millimetre away from us, but we would be oblivious to it if that millimetre were measured in a fourth spatial dimension, while we are imprisoned in just three.

While the original prediction by Arkani-Hamed et al. predicted millimeter scale compaction, it has now become sub-sub-sub-millimeter scale after several tests have concluded that the Newtonian gravity has not shown any deviation up to sub-micron length scales (or even smaller). So to me, the paragraph above gives the wrong idea that such extra dimension are of the order of just under a millimeter scale. We know quite a bit more now. There is no longer any need to stick with "under a millimeter" when we know it should be under a micrometer, which would be more accurate.

The other part is more puzzling and I don't know why he wrote it.

That said, everything, however complicated - breaking waves, migrating birds and tropical forests - is made of atoms and obeys the equations of quantum physics. But the uncertainties of subatomic physics are irrelevant to biologists; even if those equations could be solved, they would not offer the enlightenment that scientists seek.

This, I don't understand. There are already numerous examples of QM effects in biological system. I've mentioned a lecture given by Seth Lloyd at the Perimeter Institute. And we now have many reports of QM effects in photosynthesis. Someone like Rees should be aware of such advancement. So why would he made a statement that gives the impression that quantum mechanics offers no "enlightenment" to biologists?

{scratching head}



AcLa said...

He probably meant, not "quantum mechanical effects are irrelevant to biology" but rather "knowing the microscopic laws is not the same as knowing the macroscopic laws".

His next paragraph seems to support this interpretation, as it starts with "Each science has its own autonomous concepts and laws".

ZapperZ said...

Unfortunately, that doesn't make it any clearer. If he's referring to emergent phenonmena (which I've covered already in several blog entries), then why would this be restricted biological systems? The whole of condensed matter physics is, in principle, dealing with emergent phenomena.

Furthermore, just because we are dealing with a system composing huge number of particles, it still doesn't mean that QM isn't applicable. Again, as in condensed matter, we still use QM to describe such many-body system. So while microscopic laws may not be the same as macroscopic laws, QM have been shown to still applicable in both systems.


AcLa said...

I don't think he restricts it to biological systems, it looks more like it's just an example that he chose to use for whatever reason.

I don't see that he claims that QM doesn't apply. I think a crude way to paraphrase it would be "knowing the Schrodinger eqn doesn't help you understand turbulence". I understand that you know this (and guess you agree), all I am saying is that I think this is all he's saying (but with biology instead of turbulence...).

But perhaps I am misinterpreting the article and it's really claiming that QM breaks down in biological systems.

sudheer s. said...

well i agree with AcLa.But I don't understand what he means by"each science has its own autonomous concepts and laws".I believe or rather heard that all sciences are interlinked.I don't get that "autonomous" part.

Eric said...

Your line for the sub-micron experiment currently points to an older blog post of yours, a post about a measurement down to 50 microns. If there's a recent measurement on the sub micron scale, I'd love to see a link to it.

Eric said...

Sorry if I double-post.
Could you include a link to the sub-micron measurement you mentioned? The link shown is to a post about an older, >micron measuement, I think.