The end of the world as we know it?

Scaremongers have warned that the collisions at Cern could unleash incalculable danger and perhaps even destroy the Earth. Michio Kaku puts some fears to rest
Artist's impression of a supernova explosion
Photograph: Nasa/AP

Back in 1910, the media correctly reported a most unusual event: the Earth would soon encounter a celestial body in the heavens - and pass through the tail of Halley's Comet. The media also correctly stated that the tail contained poisonous gases. This soon sparked an episode of mass hysteria that suddenly gripped the public. Overnight, would-be prophets sprung up at street corners warning of doomsday. People were frantically buying gas masks and home-made remedies to ward off the poison gas. Wild rumours fed on each other, stirring up even more panic among the public.

But the media failed to report the full truth, that the tail of Halley's comet was rarer than the finest vacuum on Earth, and that all the debris and gas inside the tail could probably fit inside something like a suitcase. So when the Earth finally passed through the tail of the comet, nothing happened.

Now the media is correctly reporting that some physicists believe that the Large Hadron Collider might produce mini black holes in its collisions, and that black holes are in general so powerful that they can swallow up not just the Earth, but whole star systems. The media also correctly reported that physicists, when pressed, cannot completely dismiss the chance of being eaten alive by these mini black holes from the LHC.

This in turn has sparked some rather sensational headlines, leading up to a lawsuit filed in the US District Court in Hawaii in March, where seven people are asking for a court injunction to stop the experiments at the LHC, stating that the mini black holes it produces could grow by swallowing matter until they become large enough to swallow up the entire Earth. Although the equipment is based in Europe, and is hence outside the jurisdiction of US law, many of its large magnets and key components come from the US. The lawsuit could, theoretically, cripple the project.

These headlines may sell newspapers, but the media conveniently downplay, or even omit, giving the full picture. First of all, mother nature can produce subatomic particles of greater energy than the puny LHC in the form of cosmic rays. These high-energy particles, which are accelerated to astronomical energies by huge magnetic and electric fields in space, have been raining down on Earth for billions of years, plenty of time to swallow up the planet - yet we are still here to write about it.

Secondly, these mini black holes are not just small black holes; they are actually subatomic in size, comparable to electrons or protons. The entire energy created by these particles would not even light up a light bulb if the LHC were running for a hundred years. Although the subatomic particles produced by the LHC can have trillions of electron volts, the LHC is expected, at best, to create mini black holes at the rate of one per second, which is much too small to cause any appreciable danger to anyone.

In the same way that animals from the cat family come in all sizes, from ferocious lions to harmless domestic cats, black holes also come in all sizes, from the astronomically colossal to the totally insignificant.

Thirdly, these mini black holes are unstable, and quickly decay. Instead of gobbling up matter and becoming big enough to eat up the Earth, they go in the opposite direction, emitting radiation so that they eventually disappear into nothing, a process proposed by the renowned Cambridge physicist, Stephen Hawking. So these subatomic black holes naturally self-destruct.

Some critics have claimed that these mini black holes might get captured by the Earth's gravitational field, but they decay too quickly for them to be a danger to anyone.

Fourthly, when pressed by journalists to flatly declare that the worst case scenario cannot occur, physicists shy away, not because we think the event might occur, but because of a loophole in the quantum theory. Because of Werner Heisenberg's uncertainty principle, there is a tiny chance that anything will occur. There is a chance that firebreathing dragons will be produced by the LHC. But the probability of this event is so small, one can show that it will not happen in the lifetime of the universe.

In my opinion, if an event is so rare that it will probably not happen in the lifetime of the Universe, then we physicists should say to the media that it will not occur, period. We physicists have to be more media savvy, and not split hairs. The final nail in the scaremonger's coffin is that many of their fears against the LHC are identical to the ones used against the Relativistic Heavy Ion Collider in Brookhaven National Laboratory in New York State, a much smaller machine that has been running successfully for years without incident.

So who is to blame for the current concern about the LHC? The media and fearmongers are mainly to blame; but physicists are as well, because we have failed to adequately convey the purpose and the scope of the LHC to the public and the media. During the cold war, whenever physicists in the US wanted funds for a new particle accelerator, we would bypass the public and simply go to Congress and say one word, "Russia!" Congress would get scared, whip out a chequebook and say two words, "How much?"

This is not because these particle accelerators had any direct military value in the cold war. But Congress was worried that the US would lose its edge in a crucial area of high technology and wanted to compete with Russia's increasingly powerful particle accelerators. Well, now it is obvious that Russia is not building huge atom smashers anymore, and politicians are wary of funding them.

Now, we have to appeal directly to the public to support basic research. We physicists have to sing for our supper, just like all the other interest groups fighting for their share of the pie. As with Halley's Comet and now the LHC, history seems to be repeating itself, the first time as tragedy, the second as farce.

It is easy to forget that the US had begun building a much bigger particle accelerator in the 1990s, called the Superconducting Supercollider, which was cancelled by Congress in 1993. In the last days of hearings, one congressman asked an important question: "Will we find God with this machine? If so, I will vote for it." The poor physicist at the hearing was thrown by the question and failed to give a convincing answer, and the SSC was soon cancelled - the whole business of digging a hole for the SSC and filling it in cost $2bn of US taxpayers' money.

Since then, we physicists have replayed that scene over and over again in our minds. How should we have answered that question?

I don't know, but I would have said the following: "God. By whatever signs or symbols you ascribe to the deity. This machine, the supercollider, will take us as close as humanly possible to his or her greatest creation, genesis. This is a genesis machine, designed to study the greatest event in all history: the birth of the universe."

· Michio Kaku is professor of theoretical physics at the City University of New York. His latest book is Physics of the Impossible