Sorry this is a bit long–I’m trying to cram quite a lot of science into a rather small space–but not at anything like the speed of light 😉
Wednesday was the “start-up” of the Large Hadron Collider at CERN. As I’m sure you all know…
Encouraging the insanity
What should have been an exciting day was marred for me by all the persistent “end-of-the-world” hype in the media and on the Internet. There was a news report of a teenage girl in India who believed the stories enough to kill herself: she thought that when it was switched on, the Earth would be swallowed up by a black hole. It makes me angry that there’s so much misinformation around, both about what is/was being done and about the “likely” effects.
It makes me particularly angry to hear that small children, who one would hope would be getting excited about science in the same way that we as children got excited about space when we saw the moon landings, have instead been going around terrified of the end of the world.
Now, not everyone understands particle physics. But surely simple explanations are possible which address people’s fears. And one would hope that the media would search these out and pass them on.
OK, maybe that was a reckless statement, because I now have to try to write a simple explanation myself. And I’m not a particle physicist, just someone who did a physics-related subject at university. But here goes. [Edit: someone has now helpfully pointed out that as a blogger, I am one of the media. Hmmm…]
What are they doing?
Eventually (but not on Wednesday): trying to bash protons together at very high speeds, i.e. with a lot of energy. A proton is the heavy bit in the middle of a hydrogen atom. If you do this hard enough, the actual energy of the collision is converted into extra particles. One hope of the experiment is that these will include the famous Higgs Boson which everyone wants to find. Being a particularly heavy particle if it exists, it needs a lot of energy to make it, which means incredibly high speeds.
Wednesday: simply tests to check that a beam of protons, going at speeds that have been in use for years–not at the colossal speeds hoped for in future–could make it all the way round the 27-km circuit in a clockwise direction. Then a similar test to see if another beam could get round in the anticlockwise direction. No ultra-high energies. Not even two beams colliding with each other. Lots of very relieved engineers who’d spent years of their lives working on the project finally getting some indication that the machine might work. Bottles of champagne.
Given that what happened on Wednesday wasn’t even really new, it’s hard to see why so many people thought it was going to end the world. Unless maybe THE MEDIA didn’t bother to find out the facts properly and report them responsibly… Perish the thought.
Is it going to destroy the world, then?
We’ve heard a lot about various speculative ways for this to happen. Sadly we’ve heard a lot less about why nobody in the physics community thinks they’re the least bit likely. I suppose “nothing will happen” and “science fiction is fiction” aren’t really news. They’re not even particularly exciting. So they don’t get reported. I also suspect that to the physicists, who are intimately familiar with the science, the idea seems so fatuous that it barely seems to need explaining. Would you expect someone to come and ask you to explain why sailing over the horizon won’t make you drop off the edge of the world? No, because you’d have to change your whole view of the world you deal with every day.
CERN has produced a quite informative Safety page. What follows is a summary of that, with some additions from other sources. The CERN page also includes links to various safety reports and relevant scientific publications.
The experiment has happened already
In fact, it happens all the time. I’m talking about cosmic rays.
These are particles from space which routinely hit the earth, some at extremely high energies–considerably higher than the LHC is aiming for. So, in fact, the LHC experiment (and more energetic ones) is effectively happening in the Earth and its atmosphere every day. But at random and mostly without any fancy detectors to observe it. The LHC safety page points out that the Earth has already been hit by the cosmic-ray equivalent of about a million LHC experiments. Oddly, it still hasn’t been destroyed.
Is it really like cosmic rays, though? After all, cosmic rays don’t arrive all bunched together in a very thin beam. Might this make a difference? After all, we’ve got lots of collisions happening close together… Well I asked someone at the LHC about this and it turns out that the collisions are still WAY too far apart to have any effect whatever. So yes, it’s like cosmic rays.
Ways the world won’t end
Black holes: Could the LHC produce an earth-swallowing black hole? Well…
- Standard theory says it can’t produce black holes at all. But if that’s wrong, then
- the theories that think it can all say that the black holes would disappear in a tiny instant and have no chance to start growing.
- a black hole that could grow and swallow its surroundings would need to start off as heavy as Mount Everest anyway. (Imagine trying to stuff a whole mountain into the machine and accelerate it to almost the speed of light…)
- If the LHC could swallow up the earth in a black hole, then so could the cosmic rays which keep hitting us. Not only haven’t they succeeded, but there’s no sign that its happened anywhere else in the universe either.
Vacuum bubbles: As I understand it, these are part of a speculative theory where regions of the universe could “flip” into a different state, where matter would have different properties and we could not exist.
- If the LHC could cause this, then high-energy cosmic rays would already have done it. The LHC is quite weedy in comparison
- and actually there’s no evidence of ANYTHING having caused it anywhere in the observed universe.
Strangelets: the idea here is that the LHC produces a tiny lump of an exotic kind of matter, which then converts ordinary matter to strange matter when it comes in contact with it.
- This is the opposite of what strange matter would be expected to do. If it can exist, it’s expected to convert itself immediately to ordinary matter.
- The “possibility” was however explored before the start-up in 2000 of another machine, the Relativistic Heavy Ion Collider or RHIC, which was far more likely than the LHC to produce strangelets. Eight years on, it still hasn’t managed to produce any.
- The particles to make strangelets can only stick together if they’re travelling slowly enough; the LHC simply bashes things together too fast. If the RHIC couldn’t do it, the RHC hasn’t a chance.
Magnetic monopoles: These are hypothetical particles a bit like magnets with only one end. (I have trouble imagining them!). Some theories think they could do nasty things to the protons in ordinary matter. However,
- the theories that say they can do this also say they’re too heavy for the LHC to produce.
- if the LHC could make them, then the cosmic rays that hit us are already making them, and have been for billions of years, with no ill effect.
So they’re either impossible for the LHC to make, or safe and here already.
Links
Acknowledgement
I would like to thank Seth Zenz at the LHC for answering my question about the concentrated beam, and for taking the trouble to read through this post to check I’d represented the science accurately.
The Other Blog Without A Name 