Will new collider create black holes that destroy us all?

Visitors stand in front of the ATLAS detector at the Large Hadron Collider near Geneva. (Salvatore Di Nolfi, Keystone/Associated Press)

The Large Hadron Collider is a particle accelerator collider being built at the European Laboratory for Particle Physics, or CERN, straddling the French-Swiss border near Geneva. It should be completed and ready to start producing data sometime this summer. In it, scientists will be able to smash protons travelling at more than 99.99 percent of the speed of light with protons traveling in the opposite direction at the same speed.

Protons are actually pretty complicated objects, made of little bits and pieces, and in a collision of two protons it can happen that two of the little pieces find themselves very close together. Those pieces carry a lot of energy, and due to Einstein's E=mc{+2} one might imagine that a lot of mass in a little space could lead to a black hole.

The odds of this actually happening are pretty much zero for several reasons. First of all, the theorists who worry about such things happening make assumptions that the energy needed to make a black hole is vastly less than what we would expect in the real world as we know it. This possibility only arises in theories with what are called "large extra dimensions," and there is no evidence at all that these describe reality.

A second reason: Black holes, strictly speaking, are theoretical constructs. Nobody has ever seen a black hole. Things that are black hole candidates are objects which are known to be small and to have very high masses, but if one is very honest, there are a lot of problems with the black hole concept, and we don't yet know for sure that they really exist. One particularly vexing problem is that time is predicted to slow down as one approaches a heavy object, so that bits of matter falling into a heavy collapsing object actually take an infinite amount of time to fall in from the point of view of an observer outside.

A third reason is that while we physicists are all excited about the collisions to take place at CERN soon, such collisions take place all the time on Earth, the moon, and everywhere else due to ultrahigh energy cosmic rays. In other words, the experiments people worry about at CERN have been going on now and then at random all over the place for billions of years, and things seem to be fine!

Dr. Knowledge is written by physicists Stephen Reucroft and John Swain, both of Northeastern University. E-mail questions to drknowledge@globe.com or write Dr. Knowledge, c/o The Boston Globe, PO Box 55819, Boston, MA 02205-5819.

• Searched
• E-Mailed