This Wednesday (September 10), the world’s most powerful high-energy physics experiment will begin operation.  The Large Hadron Collider (or LHC), part of the European international experimental facility CERN, is one of the most anticipated projects in all of physics for many years.

So what does the LHC have to do with astronomy?  Why is your intrepid planetarium director excited about this, when it doesn’t seem to have any relation to the usual stuff we talk about in the planetarium?  The answer lies in the mysterious substance known as dark matter, which comprises more than 20% of the contents of our universe.  In contrast, ordinary matter—atoms and molecules, which is the stuff of our bodies and our planet—only makes up about 4% of the contents of the universe.  (The rest is an even more mysterious substance known as dark energy, a subject best left for another essay!)We don’t know many facts about dark matter.  Unlike regular matter, it is completely transparent to light:  light shines through it without being reflected, refracted, absorbed, or anything normal like that.  We know about its existence through its gravity:  we can see how dark matter affects the behavior of galaxies and galaxy clusters, and how it influences the behavior of the universe as a whole.  But what is it, really?

Enter the Large Hadron Collider.  This instrument is designed to accelerate heavy particles to a high fraction of the speed of light and smash them together.  The resulting collisions will produce cascades of new particles, including (hopefully) some new ones nobody has detected before.  If dark matter consists of various types of particles known as weakly-interacting massive particles (WIMPs), it is possible the LHC will find them.  Likewise, if they are members of the zoo of particles predicted by supersymmetry (SUSY) theory, they might show up in the detector.  Both SUSY particles and WIMPs are conjectural right now, but if their predictions have any validity, the LHC is a good way to find out.  Finding either a WIMP or a SUSY particle would take us a long way towards solving the dark matter problem, and thus identifying 20% of the missing stuff the universe is made of.

One more quick note:  there has been a lot of buzz about the LHC bringing about the end of the world.  According to some scientists, there is a probability that the LHC could produce a small black hole, which if things went really wrong could grow quickly and destroy the Earth.  The calculations are pretty unreliable when discussing black holes that small, however, and what we do know about tiny black holes is that they are very short-lived—they evaporate almost instantly by the process known as Hawking radiation. Thus, since any black hole produced by the LHC would be very small, its lifetime would be typically too short to cause any damage before evaporating.

So, I can’t reassure you that the LHC won’t destroy the Earth, but I would place extremely low odds on it doing so!

Posted by Matthew R. Francis under Science Ideas & Science News |