Be afraid! Be very afraid! Those evil particle physicists are at it again with their massive high-energy colliders, and if they're not closely monitored, their high-falutin' "experiments" might put an end to the universe as we know it. This could be doomsday, people, the ultimate Apocalypse! At least that's what an average citizen might think if they happened to stumble on this little item on Slashdot, which Jen-Luc Piquant found courtesy of the mystery blogger behind Angry Physics. It resurrects the rumor of universe-destroying mini-black holes that could be created once CERN's Large Hadron Collider goes online in -- is it 2008? I haven't been keeping up with the official start date.
I'm sure it's just a coincidence that the item appeared on the five-year anniversary of those infamous terrorist attacks on NYC and DC. Nonetheless, the smell of fear -- or at least of fear-mongering -- was still lingering in the air as various members of the Bush administration capped off a pre-election week of stumping across the nation, telling us why we should still be absolutely terrified of innocent-seeming items like bottled water and shampoo, which MIGHT EXPLODE ANY MINUTE. However, in fairness to the White House, concerns over continuing terrorist threats are much, much more valid than the worry that the LHC will end Life As We Know It On Earth -- almost infinitely so. Terrorist attacks have actually happened, and our country is still a major target of extremist groups, so a certain degree of caution should appropriately be exercised. (I still say the whole liquids and gels ban on flights is ludicrous, however.)
Even in physics, one shouldn't dismiss a potential risk outright, particularly since the LHC will achieve unprecedented energies that will hopefully lead to exciting new physics. "New physics" implies that scientists could find something surprising, or revolutionary, which could in turn be potentially dangerous. After all, Wilhelm Roentgen never dreamed in 1898 that his newly discovered x-rays could be fatal in large doses -- the proverbial double-edged sword. But in case people have forgotten, this isn't the first time we've heard about mini-black holes being produced in colliders. Brookhaven's Relativistic Heavy Ion Collider (RHIC) generated all kinds of world-ending rumors when it fired up in 1999, prompting the Sunday Times of London to print an hysterical article with the headline, "Big Bang Machine Could Destroy Earth!" Congress called for special hearings, and legend has it that one reporter called Brookhaven to ask whether RHIC had already created a black hole that swallowed the plane of John F. Kennedy Jr. as it flew past Long Island. (I would like to think this story is apocryphal, but alas, it probably isn't.)
Most of the RHIC hysteria centered not on mini-black holes, but on strangelets: an object formed should strange quarks stick around long enough after a high-energy collision to combine with up and down quarks. If a resulting strangelet had a negative charge -- an even more unlikely prospect than a strangelet forming in the first place -- it would gobble up all normal matter it encountered, until the entire universe was converted into strangelets. Aiee! Fortunately, the probability of this happening is, at best, on a par with winning the lottery not just once, but more than 10 times in a row. And that's an optimistic estimate. My favorite quote at the time was by MIT physicist Robert Jaffe, who told New York Newsday that, with regard to the formation of strangelets, it was more likely that "a spaceship is going to land in the middle of Texas, and that aliens are going to come out and tell us that the New York Yankees are all aliens."
My point is that both of these prospects have been carefully studied, in depth, by a panel of top-notch experts in the field, a mere 7 years ago, and found to be, well, fairly preposterous. Mini black holes might be a wee bit more likely than the formation of strangelets, but even if they are produced, they wouldn't pose a threat. Why is that? You might well ask. Two words: Hawking radiation. Back in the 1990s, Stephen Hawking showed that black holes can emit tiny particles of radiation, which cause them to lose mass over time, gradually winking out of existence. It's the result of virtual particle pairs popping out of the quantum vacuum near a black hole. Normally they would collide and annihilate into energy, but sometimes one of the pair gets sucked into the black hole, resulting in an apparent violation of energy conservation. The mass of the black hole must decrease slightly as a result to counter this effect and ensure that energy is still conserved. How fast it evaporates depends on the black hole's size: the smaller it is, the faster it evaporates. Ergo, even in the event the LHC produced mini black holes, they would be roughly the size of an electron, and would evaporate in mere fractions of a second.
Ultimately, the best argument against the latest "mini black holes" doomsday scenario is the same as for RHIC and its hypothetical strangelets: it hasn't happened yet in the earth's atmosphere, which is routinely bombarded by cosmic rays, and has been for billions of years, yet no evidence for strangelets or mini-black holes has been detected. Ditto for the high-energy collisions at RHIC, which has been operating for several years now. Okay, that last bit is not quite accurate: there's some debate among particle theorists about whether RHIC has produced a fireball with properties strikingly similar to a black hole. But as predicted theoretically, whatever it was proved too short-lived to pose a catastrophic risk; it wasn't even around long enough to collect much data beyond the mess of squiggly lines pictured at right.
Neither the RHIC nor the LHC doomsday scenarios are unique in modern physics history. During the years of the Manhattan Project in the 1940s, there were concerns that a nuclear explosion would set the Earth's atmosphere. (Gratuitous Morpheus quote from The Matrix: "It was we who scorched the sky.") SLAC's B factory caused ripples of doomsday concerns when it came online, and there were fears in the 1990s that Fermilab's Tevatron might create a supernova instead of (or in addition to) discovering the top quark. All proved to be unfounded.
So why does this kind of irrational panic keep happening every time a major physics experiment is slated to begin? For starters, human fear isn't logical, and we're living in an age of unprecedented scientific progress, in which the public is both fascinated by, and fearful of, what science has wrought, and what it might produce in the future. It's also an era where the knowledge gap between scientists and the average person on the street could more appropriately be termed a yawning chasm. The panic stems from ignorance of the actual physics at work. Normally this would be our cue to decry, once again, the sad state of scientific literacy (or lack thereof) in this country. And we are, indeed, still concerned about this. But in fairness to the public, sometimes physicists forget what it was like not to have a PhD in the field. Consider all the science stuff people need to know just to make sense of it all.
Thanks to popular authors like Hawking and the seeping of the notion into popular culture (Futurama played with black hole physics in one memorable episode), the average citizen probably has a rudimentary grasp of black holes and the effects of extreme gravity. But they don't necessarily know about Hawking radiation, which requires a solid grasp of concepts like matter and antimatter, virtual particles, energy conservation, and energy/mass conversions, just for starters. And they don't have a good grasp of relative size scales, so a "mini black hole" might call to mind something the size of a donut, rather than a teensy subatomic particle. Nor will they appreciate the associated physical differences related to size -- like the strength of the object's gravitational pull, for instance, or the amount of energy required to produce a top quark. (The energy to make a top quark is impressive when expressed in GeVs, but extrapolate that to the macroscale, and it amounts to roughly the energy required for an adult male to perform a single pushup.)
Matters aren't much better when it comes to the inner workings of the actual facilities. The public knows (at least one hopes they do) that physicists are smashing atoms inside giant colliders, but they don't understand that producing a mini black hole -- or a top quark, Higgs boson, or hypothetical graviton, for that matter -- requires concentrating sufficient mass into very tiny spaces to reach the literally astronomical high energies needed to recreate early cosmic conditions in the lab. And even then, it would probably require that string theory be correct in its assumption that gravity isn't as weak as it seems to be, because it can seep into extra dimensions -- meaning it would be much stronger at the Planck scales at which such dimensions might exist. So now we're asking them to be conversant in basic string theory and extra-dimensional concepts as well, not to mention the notion of a Planck scale. Given the fact that there are members of the public with active brain cells who can't even remember that the earth orbits the sun, not vice versa, and it seems a lot to ask of the average nonscientist, especially if they're distracted by the season premiere of Grey's Anatomy.
I wish I had a solution to the problem, other than to echo everyone else in calling for a redoubling of our education and outreach efforts. But sometimes it seems to be a losing battle, doesn't it? Granted, it's discouraging at times, but I still say it's a war worth waging. Otherwise, think of what a less-than-scientifically-literate layperson might make of last month's breaking news about graphene: "Black Hole in a Pencil," the Science magazine headline read.
Pencils? Black holes? What could possibly be the connection? That headline gave me pause, and I'm reasonably scientifically literate. I even know a little bit about graphene, thanks to my regular attendance at certain physics conferences. (I'm hoping to write a more extensive post on the subject at some point, but I'm still muddling through the technical details.) In essence, graphene is the two-dimensional version of graphite, the stuff of pencil lead. There was some doubt as to whether this was even possible -- for it to be truly 2D it would have to be a mere atom thick, making it also highly unstable -- but Andre Geim and cohorts at the University of Manchester in the UK succeeded in creating sheets of graphene in 2004, and have been investigating this new substance further ever since.
It's pretty exciting stuff. Much has been made of the material's potential for creating ultrafast molecular-scale transistors, especially the fact that the electrons in graphene zip along at the speed of light, as if they had no mass -- contrary to special relativity, which says no object with even the tiniest bit of mass can ever exactly reach the speed of light. Geim's latest results suggest that graphene can also shoot electrons through other materials as if they were invisible, making it possible to test the so-called Klein paradox in a tabletop experiment. (You can see nifty movies of the effect here.) It's related to quantum tunneling, in which electrons can tunnel through supposedly insurmountable energy barriers. The likelihood for tunneling decreases the higher or thicker the energy barriers that are raised, and infinitely high walls should reduce those chances to zero. Oskar Klein, however, said that if particles were moving fast enough (i.e., at the speed of light), they could pass through even infinitely high barriers. It's the kind of bizarre behavior that would normally require superheavy atoms or -- ta-da! -- black holes.
Um... That's it? That's the "connection" between pencils and black holes? I understand if you feel a bit cheated, since the connection seems pretty tenuous at best. Sure, Science was attempting to find a creative, fun little angle to liven up a potentially dry topic, but in this case, it's highly misleading. They let their own cleverness impede effective communication of the essential concepts. I guarantee the average non-scientist reader would just hear "black hole" and "pencil," and react accordingly. (On the upside Jen-Luc points out that hardly anyone outside the scientific community is likely to read Science.) Blame the editors if one day, in the near future, some poor kid taking the SATs starts worrying that his Number 2 pencil could make like a black hole at any moment, and quite possibly destroy the universe.