It's a whiz-bang experiment, with a downside that could really suck

WILL the world end later this year? In mid-August, in a chamber deep underneath the Swiss-French border, physicists will switch on a machine that might produce the first man-made black holes. Normally only found in outer space, these high-gravity objects have a reputation for devouring all matter in their vicinity — and they only stop when the food runs out. Could the Earth's first black hole also end up being its last, after it sucks in the chamber, the physicists, and the entire planet?

The possibility has had some press lately because two people are so concerned by this whoops-apocalypse scenario they've taken legal action against CERN, the European agency doing the experiment. The two litigants claim researchers haven't done the appropriate risk assessments for this mother of all science experiments.

The experiment will be carried out with the most powerful atom-smasher ever built — the Large Hadron Collider. In a few months' time, the machine will push bunches of subatomic particles round and round a 27-kilometre-long ring at almost light speed, and then bring them into a head-on collision. Rising from the debris of the impact, according to some theories, could be minuscule black holes.

Now, the CERN scientists calculate that the baby black holes' existence will be fleeting. So fleeting, in fact, they'll evaporate almost the instant they form, long before they've had a chance to gobble down the collider or any physicists. (Although they will hang around long enough for measurements to be made, allowing researchers to make some remarkable discoveries about the cosmos.) The physics community says the chance of the particle accelerator inadvertently becoming some sort of doomsday device is almost zero. But the interesting thing is, the probability is not exactly zero, so critics argue the possibility can't be ruled out absolutely.

If you're familiar with risk assessment forms, you'll have noticed there's no section for calculating accidental Armageddon. But, in what must be one of the strangest papers published in the science journal Nature, a couple of mathematical physicists have come up with a way to roughly estimate the probability that a tinkering physicist will slip up and obliterate the world. It turns out the chance of such a cosmic calamity in any one year is less than a trillion to one. But is that risk low enough?

Dealing with low risk is an issue that not only applies to atom smashers: it's relevant to every new technology that's developed. Whether it be genetically modified foods, mobile phones or new medical procedures, no matter how much testing is done it's simply not possible to prove that anything is 100% safe.

Critics point out that one way of putting any risk into context, including the collider risk, is to work out just how bad the consequences of an accident would be. Having your entire planet slurped into a hole in the space-time continuum is a fairly high-impact outcome. And, according to an even more extreme (but highly speculative) theory, that may not be the worst of it.

The atom-smasher could unexpectedly cause what physicists innocuously describe as "a transition to a lower vacuum state". The consequence of this brand new vacuum state would be a wave of obliteration emanating from the Earth at the speed of light that would eventually annihilate the observable universe. Now that'd be a cosmic cock-up!

Should the physicists be stopped from switching on their machine? Well, it's important to keep in mind that there are plenty of wild theories out there in physics, and most of them are eventually proved untrue. Plus, odds of less than a trillion to one are pretty low. For example, the chances of civilisation being destroyed by a killer asteroid from space are way higher.

And the Nature paper outlines another scenario that is far more likely than any scientist bringing on doomsday. It turns out nature has her own atom-smashers. Particles travelling near the speed of light are continually whizzing through the galaxy. These cosmic rays crash into the atoms in our planet's atmosphere with an impact far greater than will be achieved by the CERN atom-smasher.

Nature's atom-smashing experiments have been going on for the 4½ billion years the Earth has been around and no world-ending black holes have been created so far. Indeed, the paper in Nature estimates that the risk of one of these natural particle colliders ending the world is 1000 times greater than the chance of us doing it.

Of course physicists should be able to switch on their collider and start making some of the remarkable discoveries about our universe that await. The machine promises to explore exciting territory: finding more of the cosmos' fundamental building blocks, for example, and perhaps even unearthing new hidden dimensions.

Graham Phillips is the presenter of ABC TV's Catalyst and a former astrophysicist. grahamp@bigpond.com

Related

Gauging a Collider’s Odds of Creating a Black Hole

Asking a Judge to Save the World, and Maybe a Whole Lot More

LHC - Large Hadron Collider - Messing with the unknown