The Dark Side

Off and on, we've been discussing the progress economics has made as a discipline. In those discussions, we often hear what a sorry state economics is in, that the theoretical models don't predict well, that economics isn't a real science, and so on. A comparison to physics often comes up.

One response to this onslaught against economics is to point out that physicists also have a theory that doesn't predict well, in particular the motion of galaxies and the matter within them is at odds with theoretical predictions. Visible matter cannot account for the gravitational "stickiness" of clusters of matter.

The solution physicists have adopted is not to question the theory, at least not for the most part - see below, but instead to make stuff up - dark matter, dark energy, I expect there will be a "dark light" soon as well - whatever is needed to make the equations work must exist.

When I respond to attacks on economics by pointing out that these theories seem every bit as controversial and uncertain as ours, in fact perhaps more so with this "making stuff up" step that assumes the theory is correct and then assumes the matter needed to make the theory work is present in just the right invisible amounts to get motions to agree with theory, I get told it's because I don't understand (and let's not get into the vacuousness of string theory - when I say the absence of testable predictions makes string theory philosophy, not science, I guess I don't understand either).

I'm going to get myself in trouble again by not understanding one more time. This is an astrophysicist from a blog in the NY Times called Across the Universe:

Searching for the Dark Side, by Chris Lintott, Commentary, NY Times: ...The ... kind of matter we – and everything we can see directly – are made of accounts for only a sixth of the total mass in the universe. In the absence of knowledge, we label the rest as “dark matter” and look to detect it via its effects on what we can see.

We have long known that there is more to our universe than we can see. The great eccentric of American astronomy, Fritz Zwicky, realised in 1930 that the galaxies within galaxy clusters were moving more rapidly than they should be. The only explanation was to assume that there was more matter present than scientists had thought... A similar problem exists on the scale of individual galaxies; if only the visible disk of a galaxy such as the Milky Way existed, the galaxy would fly apart in just a few million years. The solution is the same; if the Milky Way is embedded in a halo of dark matter, then all is well.

What is this dark matter? We know very little about it... [M]ost cosmologists now believe that dark matter is composed of slow-moving exotic particles that have yet to be identified.

Such a situation is unsatisfactory to say the least. Although particle physicists are working on the problem, ... it is embarrassing not to know what the main component of the universe is. The alternative is to assume that there is something wrong with our knowledge of gravity, and that the work of Einstein needs revising. Theories that attempt to do just that have been somewhat successful. ...

[It will be] a stringent test for theorists attempting to dispose of dark matter, but I for one hope they succeed. It would be tidier, somehow, to lose the enigmatic dark matter, and exciting to discover a successor to Einstein’s relativity. As George Bernard Shaw said in 1930, “Ptolomy invented a universe and it lasted 2000 years. Newton invented a universe and it lasted 200 years. Now Dr. Einstein has invented a new universe, and no one knows how long this one is going to last.”

"[I]t is embarrassing not to know what the main component of the universe is." That's why economists should hang their heads in shame when real scientists enter the room.