Awhile ago I wrote about Lisa Randall, Professor of Science at Harvard University, a theoretical physicist and cosmologist, who proposed that the dinosaurs went extinct due to the actions of unseen dark matter.¹ There now appears again an article in the popular science magazine Nautilus with the title “Does Dark Matter Harbor Life? An invisible civilization could be living right under your nose.”² It would appear to be excerpted from Randall’s book Dark Matter and the Dinosaurs. In the article Randall asserts that we may, in fact, be kind of racist against dark matter, well, at least, we are biased towards ordinary matter, where, she claims, in fact, that dark matter is the stuff that holds galaxies together so it is really important stuff.
The common assumption is that dark matter is the “glue” that holds together galaxies and galaxy clusters, but resides only in amorphous clouds around them. But what if this assumption isn’t true and it is only our prejudice—and ignorance, which is after all the root of most prejudice—that led us down this potentially misleading path?
People in foreign relations make a mistake when they lump together another country’s cultures—assuming they don’t exhibit the diversity of societies that is evident in our own. Just as a good negotiator doesn’t assume the primacy of one sector of society over another when attempting to place the different cultures on equal footing, an unbiased scientist shouldn’t assume that dark matter isn’t as interesting as ordinary matter and necessarily lacks a diversity of matter similar to our own.² (emphasis added)
She goes on to promote the possibility of dark life, invisible creatures living on dark planets around dark stars in dark parts of galaxies. She suggests dark matter may be much more than just amorphous matter, but have a rich life with dark forces and therefore this implies a dark invisible universe of creatures we cannot detect. Sure sounds like good material for a sci-fi story.
Partially interacting dark matter certainly makes for fertile ground for speculation and encourages us to consider possibilities we otherwise might not have. Writers and moviegoers especially would find a scenario with such additional forces and consequences in the dark sector very enticing. They would probably even suggest dark life coexisting with our own. In this scenario, rather than the usual animated creatures fighting other animated creatures or on rare occasions cooperating with them, armies of dark matter creatures could march across the screen and monopolize all the action.
But this wouldn’t be too interesting to watch. The problem is that cinematographers would have trouble filming this dark life, which is of course invisible to us—and to them. Even if the dark creatures were there (and maybe they have been) we wouldn’t know. You have no idea how cute dark matter life could be—and you almost certainly never will.
Though it’s entertaining to speculate about the possibility of dark life, it’s a lot harder to figure out a way to observe it—or even detect its existence in more indirect ways. It’s challenging enough to find life made up of the same stuff we are, though extrasolar planet searches are under way and trying hard. But the evidence for dark life, should it exist, would be far more elusive even than the evidence for ordinary life in distant realms.
Dark objects or dark life could be very close—but if the dark stuff’s net mass isn’t very big, we wouldn’t have any way to know. Even with the most current technology, or any technology that we can currently imagine, only some very specialized possibilities might be testable. “Shadow life,” exciting as that would be, won’t necessarily have any visible consequences that we would notice, making it a tantalizing possibility but one immune to observations. In fairness, dark life is a tall order. Science-fiction writers may have no problem creating it, but the universe has a lot more obstacles to overcome. Out of all possible chemistries, it’s very unclear how many could sustain life, and even among those that could, we don’t know the type of environments that would be necessary.² (emphasis added)