ATLAS, one of the experiments in the Large Hadron Collider. Photo by CERN

The Large Hadron Collider will power up on today. From the popular news it looks like scientists will be charging up a death ray to cause the end of the world for no good reason. My feelings about the critics are mixed. The fact that a lot of people in lab coats say it's safe isn't enough to make it safe. One comment on the BBC website was "let's hope these scientists know what they're doing," and that's exactly the wrong attitude to have. People are right to challenge any bland assertions and ask for evidence. At the same time the people warning people are "meddling in things they don't understand" are resorting to the worst stereotypes of superstition. Of course scientists are meddling in things they don't understand. If they understood what was going on it'd be a waste of billions of pounds to pay people to meddle with them.

So how do you find out if the Large Hadron Collider is safe without spending years studying particle physics?

One way is to look at why physicists want to build it. The LHC is a very strange device. It's the collider that will be large. The hadrons themselves will be extremely small. They're protons or lead ions which will be accelerated to race round the LHC in a large loop. The beam will be directed rather like the way the cathode-ray tubes work on old televisions and computer monitors, though they direct electrons rather than protons and they don't tend to be loops over sixteen miles long. Perhaps "not like a television" would be a better analogy. Once they have this beam of high-energy particles, scientists will then smash it into another beam coming in the opposite direction and hope to watch the debris.

The beams will produce an uncounted number of collisions. What physicists hope is that they'll catch enough of these to see what is inside a proton. So far there's a popular model proposed for how the universe works. If they see some of the particles that were predicted it suggests they're along the right lines. If they don't see anything they'll be even more excited, because that means the universe is much stranger than they thought. Then they'll work about how to sell that to the public, because it's difficult to get people excited when your message is "We've found nothing, isn't that wonderful?"

Target number one is the Higgs Boson. This is the particle that gives things mass. This sounds simple enough, we don't even need to see because we all know we have mass every time we step on the bathroom scales. In fact we know very little about how that mass got there. We don't even know if there's one Higgs particle or many. This has serious implications when we look at the cosmic rays which smack into the atmosphere.

The scare stories come from the other things which might be found. One concern is that the collider might produce mini Black Holes. As everyone who's seen the Disney documentary on the subject, there's a danger that the world could be overrun by deadly red robots. That's far more likely than the alternative proposed by some other people because as violent as these explosions are, they won't exceed the bombardment by cosmic rays that the Earth has suffered since its formation.

Another way to find out if it's trouble is to see what other physicists, who have less money for their work, say about it.

Unsurprisingly some of them they say it's a lot of money for little outcome and the money could be better spent elsewhere. This isn't necessarily just sour grapes. The LHC will be putting huge amounts of energy into these particles and as everyone knows e=mc². That could be a problem if you want to see where mass comes from because the m in that equation is mass. Particles accelerated to high speeds might not behave the same as particles at lower speeds. However what these same physicists are not saying is that the LHC will cause the end of the world. If there was any conceivable chance then wouldn't that be the best reason to get the project shut down and the money spent elsewhere?

This doesn't mean the LHC will be problem-free or that we shouldn't keep an eye on it. Nasty surprises can come from where you don't expect them, ask anyone who's brushed their teeth with radium toothpaste but you can get unexpected benefits too. The universe is not a safe place. In 1994 the comet Shoemaker-Levy smacked into Jupiter with a force that would have meaningfully meant the end of civilisation if it had hit Earth. Yet sooner or later a similar event will come our way, on the whole it's safer to know more about the cosmos so you have a better chance of defending yourself.

Still if you're disappointed that the world will not be ending today then I highly recommend the website Exit Mundi, which will tell you how it will end.

Cartoon by Nick Kim at Lab Initio.