The curious wavefunction the difference between chemistry and physics gsa 2016 catalog

‎"Chemistry is not ‘physics with less rigor’. In chemistry there are discoverable guiding principles for systems which are too complex for a "first principles" approach. The nature of chemistry is very difficult to explain to most physicists, in my experience!" In chemistry there are emergent phenomena that cannot be simply reduced to physics. One has to think at the level of molecules and not just atoms, especially for understanding chemical reactions. This is especially true for understanding biochemical reactions. Knowing about quarks won’t directly help you to understand the structure of DNA but knowing about hydrogen bonds definitely will. Of course the same caveats apply to thinking about biology as ‘applied chemistry’. The fact is that every science comes with its own set of fundamental laws. These laws are strictly reducible to ‘lower-level’ laws in a philosophical sense, but the lower-level laws don’t directly lead to the higher-level fundamental ones. Thus, an understanding of the lower-level laws, no matter how thorough, does not automatically imply an understanding of the higher-level ones.

Even without having read the books and articles about the philosophy of chemistry, it is proven by mathematicians that even when you know all the basic rules and the exact starting environment that make up together an entire world, one can not predict the results for a longer period and on larger scale. This is easily shown by Langton’s Ant:

At first, all seames well defined ans simple, but when time passes by and when the system becomes more complicated and larger, a chaotic behaviour appears. Although many mathematicians have tried to find some sort of function to prove the ant’s behaviour, nothing so far seems to work, exept for the step-by-step approach. And then suddenly, after the chaotic period, some certain order emerges. The order is also not predictable when one only knows about the starting terms.

Applied to the discussion about chemistry and physics: even although physics might once find a way to completely discribe all forces acting on a whole molecule existing of thousands of non-hydrogen atoms, it would probably be not suited for describing what happens when a large quantity of acid is mixed with a large amount of a solution of two bases.

Take for instance the 1996 Nobel Prize in Chemistry awarded to three chemists "for their discovery of fullerenes". How it was discovered? According to this article http://www.azom.com/Details.asp?ArticleID=3499: “The serendipitous discovery took place during experiments involving a cluster beam which uses a laser to vaporize a graphite rod in a helium atmosphere to produce carbon plasmas. The research was aimed at characterizing unidentified interstellar matter.”

Hence it was discovered by accident and not by applying any deductive process to it. It doesn’t make it less relevant, but is a typical chemistry discovery, more the sub-product of another project rather than the confirmation of a theory or hypothesis aimed initially by the discoverers.

Now take the Nobel Prize in Physics of the same year, awarded to three physicists "for their discovery of superfluidity in helium-3". They discovered this phenomenon after several years of research in superfluidity, a phenomenon whose theory was awarded in 1962 with another Nobel Prize in Physics to Lev Landau "for his pioneering theories for condensed matter, especially liquid helium". Therefore, they didn’t get the result by accident. That is the role of a deductive science: to theorize first, to predict later and to confirm by measurements at the end.

Sometimes the chemistry-vs-physics debate is focused on the alleged “complexity” of chemistry: “In chemistry there are discoverable guiding principles for systems which are too complex for a "first principles" approach.” Lipscomb says this like if it was a revelation. But everyone in physics is pretty much aware of the fact that when the number of variables exceeds a certain limit, the system itself became intractable at a “first principles” level. Those systems are studied by the laws of statistical mechanics or the many-body theory. I wonder what advances he may be done without the help of “reductionist” instruments like NMR or X-ray diffraction.

“I recognize that many physicists are smarter than I am—most of them theoretical physicists. A lot of smart people have gone into theoretical physics, therefore the field is extremely competitive. I console myself with the thought that although they may be smarter and may be deeper thinkers than I am, I have broader interests than they have.” Reply Delete