They can’t find it, but it must be there. How long can that approach be sustained?
“Dark-matter search considers exotic possibilities,” Nature told its readers this week. How exotic? Exotic enough to be completely undetectable forever. Would that be scientific?
In October [10/30/13] the most sensitive experiment looking for proof of the leading candidate for dark matter — theorized particles called WIMPs (weakly interacting massive particles) — reported null results, disappointing scientists once again. Now some researchers are reexamining dark-matter candidates once written off as unlikely, and considering less satisfactory ideas such as the possibility that dark matter will turn out to be made of something more or less undetectable.
The article goes on to claim that evidence for dark matter is “substantial,” despite the fact that “Physicists still have no proof that dark matter exists at all”. That “substantial” evidence, however, is all indirect: motions that imply the presence of something possessing more gravity than accounted for by visible matter. Tied into the explanation is the assumption that things have been moving out there for billions of years.
If WIMPs don’t turn up, or axions (the next leading candidate), or mini black holes or quark matter, scientists will be forced into an uncomfortable position: believing in something that they cannot detect. That’s pretty scary:
The scariest possibility may be that dark matter is made of something impossible to find —some particle that interacts with regular matter only via gravity and no other force. In such a case researchers would have no hope of catching it in a detector. “If we move into a mode where our most favored particles are simply not detectable, we have the classic scientific challenge, which is how do you verify such a theory?” Gaitskell asks. “At that point you’re almost a failure — you have a theory that’s almost impossible to test.”
Such a “scientific challenge” would be indistinguishable from believing in ghosts, unicorns or fairies. They’re always just around the corner but never show up. But they must be there, because we feel their influence, don’t we? What else could it be?
Theorists continue to hope evidence for dark matter will show up. If not, they can always try the “federal-deficit” trick: leaving the bill to the kids.
“I doubt we’ve thought through all the interesting possibilities,” says theorist Matt Strassler, a visiting physicist at Harvard University. “We may get lucky” and find the answer soon, he says, “or this may drag on for 100 years or more.”
But does science get a blank check or credit card to use for a century when its promised returns don’t materialize? One searcher quipped, “As in all research, there is never a guarantee of success.” It would seem that at some point a respectable scientist would decide that a vain quest is not worth pursuing.
If these guys were investment counselors, would you trust them? There is another way out. Question your assumptions.