Preposterous Universe

 
Doubt and dissent are not tolerated

PZ Myers of Pharyngula fame has pointed me to an online petition that was apparently first published in New Scientist. No, it's not complaining about the Bush administration making a travesty of science (although David Appell points to one of those, too); it's about the terrible dominance of the Big Bang model.

The complaints are not new. The Big Bang just rubs some people the wrong way, and they won't believe in it no matter how many successes it accumulates. Some of the disbelief stems from religious conviction, but in other cases it seems to be a particular kind of philosophical outlook. Most of the skeptics, of course, have their own favorite alternatives. The most popular is undoubtedly the Steady-State model (or one of its increasingly twisted modern incarnations), but there is also something called the "plasma cosmology", championed by the late Nobel Laureate Hannes Alfven. (His Nobel was for plasma physics, not cosmology; and the fact that he was Swedish didn't hurt.) If you want to know in detail why the various alternatives are wrong, Ned Wright tells you.

Here is the kind of thing the petition says:

What is more, the big bang theory can boast of no quantitative predictions that have subsequently been validated by observation. The successes claimed by the theory's supporters consist of its ability to retrospectively fit observations with a steadily increasing array of adjustable parameters, just as the old Earth-centered cosmology of Ptolemy needed layer upon layer of epicycles.

Really? How about acoustic peaks in the power spectrum of temperature fluctuations in the cosmic microwave background? And the polarization signal, and its spectrum? And the baryon density as deduced from light-element abundances agreeing with that deduced from the CMB? And baryon fluctuations in the power spectrum of large-scale structure? And the transition from acceleration to deceleration in the Hubble diagram of high-redshift supernovae? And the relativistic time delay in supernova light curves? These are just the very quantitative predictions that have come true in the last few years; the Big Bang has had a long history of many observational successes. (This is a very incomplete list; usually one doesn't pay much attention to straightforward tests of the Big Bang framework, since they are taken for granted.)

But here is the important issue, again from the petition:

Whereas Richard Feynman could say that "science is the culture of doubt", in cosmology today doubt and dissent are not tolerated, and young scientists learn to remain silent if they have something negative to say about the standard big bang model. Those who doubt the big bang fear that saying so will cost them their funding.

Something actually interesting is being raised here: at what point does a scientific theory become so well-established that it's no longer worth listening to alternatives?

There's no easy answer. Scientific theories are never "proven" correct; they simply gather increasing evidence in their favor, until consideration of alternatives becomes a waste of time. Even then, they are typically only considered correct in some domain. Einstein's general relativity, for example, works very well in a certain regime, but that doesn't stop us from considering alternatives that may be relevant outside that regime.

So, shouldn't we devote a certain fraction of our scientific resources, or our high-school and secondary curricula, to considering alternatives to the Big Bang, or for that matter Darwinian evolution? No. Simply because resources are finite, and we have to use them the best we can. It is conceivable in principle that the basics of the Big Bang model (an expanding universe that was much hotter and denser in the past) are somehow wrong, but the chances are so infinitesimally small that it's just not worth the bother. If individual researchers would like to pursue a non-Big-Bang line, they are welcome to do so; that's what tenure is for, to allow people to work out ideas that others think are a waste of time. But the community is under no obligation to spend its money supporting them. And yes, young people who disbelieve in the Big Bang are unlikely to get invited to speak at major conferences, or get permanent jobs at research universities. Likewise astrophysicists who believe in astrology, or medical doctors who use leeches to fight cancer. Just because scientific claims are never proven with metaphysical certainty doesn't mean we can't ever reach a conclusion and move on.

And to be sure, the alternatives to the Big Bang are just silly. Usually I try to keep my intellectual disagreements on the level of reasoned debate, rather than labeling people I disagree with as "dumb" (that I reserve for the President); but in this case I have to make an exception. They just aren't, for the most part, very smart. Consider this quote by Eric Lerner, petition signatory and author of The Big Bang Never Happened:

No Conservation of Energy
The hypothetical dark energy field violates one of the best-tested laws of physics--the conservation of energy and matter, since the field produces energy at a titanic rate out of nothingness. To toss aside this basic conservation law in order to preserve the Big Bang theory is something that would never be acceptable in any other field of physics.

Actually, there is a field of physics in which energy is not conserved: it's called general relativity. In an expanding universe, as we have known for many decades, the total energy is not conserved. Nothing fancy to do with dark energy -- the same thing is true for ordinary radiation. Every photon loses energy by redshifting as the universe expands, while the total number of photons remains conserved, so the total energy decreases. An effect which has, of course, been observed.

Just because a person doesn't understand general relativity doesn't mean they are dumb, by any means. But if your professional activity consists of combating a cosmological model that is based on GR, you shouldn't open your mouth without understanding at least the basics. So if I get to decide whether to allocate money or jobs to one of the bright graduate students working on some of the many fruitful issues raised by the Big Bang cosmology, or divert it to a crackpot who claims that the Big Bang has no empirical successes, it's an easy choice. Not censorship, just sensible allocation of resources in a finite world.

~ posted by Sean Carroll at 5:11 PM ~ link ~ ~ ~