S03E15: The Large Hadron Collision

In tonight’s episode, Leonard finds he is invited to Large Hadron Collider, “the LHC”.   In case this ever happens to you,  I have a handy phrasebook at the end of the post.  (Or take it with  you if  take a  free CERN tour open to the public.)  But first, even though the LHC has had about a billion dollars of news coverage over the past two years, there may be viewers that have not have heard that the LHC is the largest “atom smasher” ever built.

“Atom smasher” is a quaint 1950’s term for a “particle accelerator”.  Particle accelerators  produce “high energy” collisions for people like me, “high energy physicists”.   As a side benefit, they  also produce the brightest visible light and X-ray sources available for study of new materials and biological systems.

How high is “high energy”?    The LHC is designed to produce collisions of protons that have been accelerated by 7 trillion volts.  That sounds like a lot.  How much?  When two of these protons collide they have  the energy you would get out of eating 0.00013 micrograms of a candy bar.

That is not much energy for a machine touted as recreating the Big Bang.   There are much higher energy collisions on a Manhattan sidewalk than this.   The key point is  that high-energy physicists care about the energy per particle.    Collisions on the highway, or even a baseball with a bat, are collisions with objects with over 10²⁷ (1 followed by 27 zeros!) particles in them.   So any one proton in the collision of two cars has very little energy compared to the LHC.

A ball and bat make a much higher energy collision that the LHC. What matters though is the energy per particle.

Even the “Big Bang machine” as an analogy is a bit off the mark.  The collisions do not make a high temperature replica of the Big Bang.  Having only two particles collide is barely enough to think about as having any temperature at all.    (Some reactions that would occur in a high temperature fluid, cannot happen at the LHC with its only two colliding particles, even though they are high enough energy…to get around this, some physicists will someday use the machine to collide large nuclei, but the high-energy frontier is the collisions of single protons.)

Perhaps a more apt, albeit less sensational, description is an old one:  High energy accelerators are giant microscopes.  A deep law of physics is that the higher the momentum of a particle, the smaller size it can resolve.   High energy means high momentum and going down this path for a few centuries brings us to the Large Hadron collider.

Optical Microscopes:  The artisan lens-makers of Flanders over 400 years ago inspired Galileo to combine lenses to make a telescope to study the heavens.    A slight rearrangement of the optics, produced a microscope, producing images of biological structures too small for the human eye, on the scale of a millionth of a meter or “micron”.   The minimum size structure visible is dictated by the “size” of visible light, about half a micron.   But a “micron” is enormous on the biological and even atomic scale.   Barely any of the structures in the nucleus of a living cell can be seen.

Electron Microscopes:   In the early 20th century, a polio epidemic spanned the world.  In 1% of its infections, polio would leave children paralyzed for life.  Optical microscopes were not up to the task of imaging the poliomyelitis virus.  So German engineers pressed into service the physics rule that high momentum means access to small sizes..  By bombarding a sample with high energy electrons, the polio virus could be seen.  (Images of structures are  in black and white.  It is meaningless to even ask the color of something so small that not even light can resolve it.  But like Ted Turner, physicists often colorize their images. )   Over the years, the technology has improved to the point where even the locations of individual atoms can be measured to 0.000000000050 meters.

Accelerated electrons allow imaging the poliomyelitis virus which causes polio (false color). This is far too small to see under a regular, optical, microscope.

The Large Hadron Collider:  and other recent accelerators are sensitive enough to offer the possibility of looking inside even a proton.   Structures the size of 0.000000000000000001 meters (that’s a billionth of a billionth of a meter) are routinely studied by high energy physics like Leonard.

Founded soon after the Second World War, CERN used physics as a proving ground for European unity in peaceful pursuits.  I spent a few years working at CERN, the home of the Large Hadron Collider.  English is lingua franca at CERN, but having been around for nearly 40 years, English spoken in this island surrounded by the French-speaking countryside of France and Switzerland has developed into a dialect of its own.   In case you, like Leonard, are ever invited to CERN here are a few helpful phrases instructing you how to speak in the CERN dialect:

“How does this look like?“:  When giving a presentation on scientific work, I often find myself asking rhetorically about the data, choosing between either “How does this look?” or “What does this look like?”.  In the CERN dialect, this hybrid phrase means you never have to choose.

Profit: In French, the verb profiter means  to take advantage of. This allows a much more efficient construction, as in “Let us profit from the sunshine and eat out of doors”.

British English: For some reason, English taught in European schools appears still to be British English, not American.  So use “autumn” for “fall”,  never use “how come?” for “why?” and so forth.

Avoid   ‘s :  Face it, the “apostrophe -s” is hard to hear, and the rules are often even screwed up by a native English speaker.   This is also not a construction that has a counterpart in many other languages.  A phrase, “Let’s go to John’s lab and look for Mike’s screwdriver” is not something you are likely to hear in the CERN dialect.  Rather say “Let us go to the lab of John and look for the screwdriver of Mike” if you want to be sure to be understood.

Replace specific English words with French ones: Occasionally the French word is substituted directly for an English one.   Being located on the French-Swiss border, working at CERN you will be crossing the border–several times a day.   “Customs Officer” is a word you’ll need, but klunky.  Replace with douanier.

For what concerns… :  Phrases do not always get shorter.  If you are concerned about your particle tracker, don’t say “Concerning the tracker”, say “For what concerns the tracker….”

Toilet: A word we avoid in polite English conversation, toilet, corresponds in French to the very clean faire la toilette.  At CERN, don’t “go to the bathroom”. There is no bathtub in there anyway.  When nature calls you can very politely “go to the toilet”.

For more information see this nice page from Francois Briard a CERN employee who is heavily involved with their public outreach.  He also sent me a link to some fun movies.

Of course any of the guys would have friends at the university that could get them into the LHC lab, including many places not open to the public on the tours.   But plane tickets to Europe, a place to stay, and especially European gasoline for getting around do not come cheaply.   So their excitement is duly warranted.

Time for a “toilet” break.

P.S.  For over a decade, in my high-energy physics class I’ve always asked the students the following question:   “Every time a new accelerator turns on, some clowns appear and say it will destroy the Earth and/or Universe.  Explain whether this is likely or unlikely.”   Sure enough, the same thing happened with the LHC turn-on.  A key point I want my students to realize  is that Nature has much higher energy particles making much higher energy collisions all around us.   Basically these guys are fear mongering with an attention-grabbing stunt.  Now just because it is fear-mongering and an  attention-grabbing stunt does not mean it is wrong.    There are always loopholes.  So it is logically incorrect to say a disaster is absolutely impossible, as some of my colleagues have said. (Or at least what the media says they said.)  In fact it is logically possible at any moment something you do in your kitchen could even create ice-9.  So I think physicists should be careful and not say “absolutely impossible” when they really mean to say “is ridiculously stupid”.

P.P.S.  That said, I have an “I survived the Large Hadron Collider 9/10/2008 T-shirt”