I’ve received a couple of comments recently about the Hadron Collider. For those of you who don’t know what I’m talking about, the collider is a $8 billion particle accelerator and considered as one of the most complex scientific equipment ever built. The main purpose if this collider is to make particles travel almost as fast as the speed of light and then make them crash into each other, thus generating incredible amount of energy.

Why the hell do we want to accelerate particles?

Well, the Large Hadron Collider UK website explains why:

The LHC will allow scientists to probe deeper into the heart of matter and further back in time than has been possible using previous colliders.

Researchers think that the Universe originated in the Big Bang (an unimaginably violent explosion) and since then the Universe has been cooling down and becoming less energetic. Very early in the cooling process the matter and forces that make up our world ‘condensed’ out of this ball of energy.

The LHC will produce tiny patches of very high energy by colliding together atomic particles that are travelling at very high speed. The more energy produced in the collisions the further back we can look towards the very high energies that existed early in the evolution of the Universe. Collisions in the LHC will have up to 7x the energy of those produced in previous machines; recreating energies and conditions that existed billionths of a second after the start of the Big Bang.

So, it is basically all about explaining what the universe is made of and what the universe was like at the time of the Big Bang. That would help us understand quantum physics a lot more and provide explanations for some phenomenons physics can’t explain. We could go in details explaining the process of accelerating particles, the effects on atoms, what an atom is made of (nucleus, quarks, etc.) but that’s not the point of this article, you can find the information elsewhere easily. I want to explain why this collider is considered by some people as dangerous while there’s nothing to be scared of.

How is this Large Collider built?

The collider is contained in a circular tunnel with a circumference of 27 kilometers (17 mi) at a depth ranging from 50 to 175 meters underground. The tunnel, constructed between 1983 and 1988, was formerly used to house the LEP, an electron-positron collider.

The 3.8 metre diameter, concrete-lined tunnel crosses the border between Switzerland and France at four points, although the majority of its length is inside France. The collider itself is located underground, with many surface buildings holding ancillary equipment such as compressors, ventilation equipment, control electronics and refrigeration plants.

The collider tunnel contains two pipes enclosed within superconducting magnets cooled by liquid helium, each pipe containing a proton beam. The two beams travel in opposite directions around the ring. Additional magnets are used to direct the beams to four intersection points where interactions between them will take place. In total, over 1600 superconducting magnets are installed, with most weighing over 27 tonnes.

What about black holes?

Some people claims that the huge amount of energy produced by the collider could result in a black hole and that this black hole would swallow Earth and distant stars. For those of you who don’t know, a black hole is so dense that it absorb everything, including light (That’s why it’s actually black). That’s also why we are orbiting around the Sun, because the sun is a bigger mass and we’re attracted by it. The difference with black holes is that their density is much more important, thus also absorbing light.

While it is totally possible for the collider to generate a black hole, it wouldn’t result in a doomsday scenario simply because we have to put everything in perspective. A black hole generated in the collider would be too small to have any sort of influence. Mangano, a member of the CERN group studying the safety of the collider doesn’t deny the possibility that the collider could spawn a black hole, but he says the energy would be concentrated in a space thinner than a human hair. That’s simply too small to even have a slight influence on us. That would be a spectacular thing though, because black holes are still a mystery to scientists.

There’s also the other fact that the energy created by smashing protons and lead ions together might not produce enough energy to create a black hole. Energy created by the collider can reach 14 trillion electron volts, but it is not widely accepted as being enough to spawn a black hole.

Other safety concerns

I could rewrite the whole thing but I think Wikipedia does a pretty good job at explaining safety concerns of the Large Hadron Collider:

Concerns have been raised that performing collisions at previously unexplored energies might unleash new and disastrous phenomena. These include the production of micro black holes, and strangelets. Such issues were raised in connection with the RHIC accelerator, both in the media and in the scientific community; however, after detailed studies, scientists reached such conclusions as “beyond reasonable doubt, heavy-ion experiments at RHIC will not endanger our planet” and that there is “powerful empirical evidence against the possibility of dangerous strangelet production.”

One simple argument against such fears is that collisions at these energies (and higher) have been happening in nature for billions of years apparently without hazardous effects, as ultra-high-energy cosmic rays impact Earth’s atmosphere and other bodies in the universe. A concern against this cosmic-ray argument is that, if dangerous strangelets or micro black holes were created at LHC, a proportion would have less than the Earth’s escape velocity (of 11.2km/s), and therefore would be captured by the Earth’s gravitational field, whereas those created by high-energy cosmic rays would leave the planet at high speed, due to the laws of conservation of momentum at relativistic speeds.

CERN’s review concludes, after detailed analysis, that “there is no basis for any conceivable threat” from strangelets, black holes, or monopoles. However, the concern about the verity of Hawking radiation was not addressed, and another study was commissioned by CERN in 2007 for publication on CERN’s web-site by the end of 2007.

The risk of a doomsday scenario was indicated by Sir Martin Rees, with respect to the RHIC, as being a one in fifty million chance, and by Professor Frank Close, with regards to (dangerous) strangelets, that ‘the chance of this happening is like you winning the major prize on the lottery 3 weeks in succession; the problem is that people believe it is possible to win the lottery 3 weeks in succession’. Accurate assessments of these risks are impossible due to the currently incomplete, or even hypothetically flawed, standard model of particle physics (see also a list of unsolved problems in physics).

Micro black holes

Although the Standard Model of particle physics predicts that LHC energies are far too low to create black holes, some extensions of the Standard Model posit the existence of extra spatial dimensions, in which it would be possible to create micro black holes at the LHC at a rate on the order of one per second. According to the standard calculations these are harmless because they would quickly decay by Hawking radiation. The concern from opposing civil society movements is that, among other disputed factors, Hawking radiation (which is still debated) is not yet an experimentally-tested or naturally observed phenomenon. Thus, the above mentioned opponents to LHC consider that micro black holes produced in a terrestrial laboratory might not decay as rapidly as calculated, or might even not be prone to decay and, if unable to rapidly evaporate, they could start interacting, grow larger and potentially be disastrous to Earth itself.

This all looks safe to me. Of course, there’s always new surprises showing up when messing up with atoms but I completely trust these scientists. I think we have enough knowledge about quantum physics to be able to predict possible dangers and protect us against them. Also, according to scientists, ‘the chance of this (doomsday scenario) happening is like you winning the major prize on the lottery 3 weeks in succession’. We have to admit it’s pretty low.

In fact, I’m really excited by this project and I’m sure great discoveries will be made!

In conclusion, there’s not much fears to have about this collider: there’s a lot of more important stuff in life to worry about.