02 August 2005

Modern Physics: The Idiot's Version.

You can understand almost everything you need to know to explain almost everything in real life with a quite simple (and wrong) set of physics theories.

In the abridged version, there are just two forces: gravity and electro-magnetism.

Gravity is Newtonian. In other words, the only thing you need to know about gravity is F=GMm/r^2, where G is the gravitational constant, M is one object's mass, m is the other objects mass, and r is the distance between them. It is for all practical purposes instantaneous.

You still need a quantum mechanics level understanding of electro-magnetism, and you still need Einstein's theory of special relativity (the speed of light speed limit and related ideas about clocks ticking at different speeds for different observers).

There are just five kinds of particles you need to know about: protons, neutrons, electrons, positrons (i.e. anti-electrons) and photons. You assume that all of these particles are stable except in situations that are beyond the scope of this simplified theory.

Everything else in the universe is relegated to "nuclear physics" and "astronomy", neither of which are relevant in the vast majority of cases in real life. For example, the abridged rules of physics I've presented above is completely sufficient for any purposes within the realm of chemistry or biology or non-nuclear engineering applications.

I say this because it is important to make clear what is at stake in modern physics. No one is proposing any changes to the laws of gravity in situations at the Earth orbit level or below in cases where Newtonian gravity is currently sufficient as an approximation of the theory of General Relativity to get the right result. No one is proposing substantive changes to QED (the theory of electromagentism). No one is proposing that special relativity is wrong in the kinds of circumstances where we ordinarily apply it.

For that matter, we really know all we need to know to create nuclear fission and fusion bombs, and to operate nuclear fission based nuclear power reactors. And, the physics of the most plausible candidates for nuclear fusion based power reactors are quite well understood. Modern physics is about understanding the universe. But, it is unlikely to have much in the way of technological benefits that flow from the theories themselves. Most scientists expect, at best, a new theory that would explain what "higher level theories" have already observed.


Kyle said...

" Most scientists expect, at best, a new theory that would explain what "higher level theories" have already observed."

Are you sure? Robert Laughlin would disagree. Most physicists are condensed matter and materials physics, and most of them would disagree as well.

Andrew Oh-Willeke said...

Laughlin appears to agree with me, even using the same language of "emergent physical phenomena" aka "higher level theories". His point is that a theory of everything would do little to expand our understanding of the universe, because the interesting part of physics involves how the fundamental theories we already understand play out, rather than how phenomena that flow from fundamental theories which we do not yet understand.

Basically, he echos my main message, which is that theory of everything research has little practical effect, despite its value in satisfying human curiousity.