Wednesday, November 27, 2013

Criteria for truth

The physicists and cosmologists tell us that the universe consists of 5% ordinary matter (the kind of stuff your chair is made of), 27% dark matter (massy stuff of a yet undetermined nature), and 68% dark energy (also yet unidentified). Dark matter and dark energy are hypothesized to exist because of their apparent effects on luminous objects -- stars and galaxies.

Which is to say, most of what is is invisible.

It's sort of like hypothesizing the existence of poltergeists to account for moving candlesticks.

With a difference. Weakly interacting massive particles (WIMPs) and axions -- the two strongest contenders for dark matter -- will only be admitted to the realm of the real if they can be empirically detected. In both cases, this requires a rather heroic experiment. You can be sure that physicists are doing their best to make the supposed culprits reveal themselves. There are reports on the current state of affairs in the 1 November issue of Science.

Some folks would say that the difference between WIMPs or axions and poltergeists are not as great as I make them out to be. OK, the candlestick moved, but what about the neighbor who reported hearing a spooky sound the same evening, or the "ghost-buster" (reasonable fees) who claims to have captured an aura on his infrared camera? Doesn't that count as empirical verification?

Not quite. Every claim for detection of a WIMP or axion will (or has been) subjected to repeated scrutiny. Every claim must be reproducible by believers and skeptics alike. Consensus is the goal. When the WIMP champions concede to the axioners, or vise versa, then we'll begin to say that nature is revealing the real.

Tentatively. And in the meantime, physicists and cosmologists work to make the bonds that hold experiment and theory together as resilient as possible.

These are constraints that poltergeists – or UFOs, or astrology, or ESP, or petitionary prayer -- have yet to meet.