Why physics needs such enormous machines to study the smallest things
Harry Cliff explains why a collider has to be so big, Don Lincoln explains how colliders and detectors work, and Lisa Randall draws lessons from the Large Hadron Collider. Their explanations answer the common question of why progress in particle physics costs so much.
Why does studying smaller things require more energy? Show answer
A higher-energy collision resolves a shorter distance, and heavy particles can only be made if the collision carries at least their mass in energy.
What does Harry Cliff say the collider is a microscope for? Show answer
The structure of the vacuum. He says the real building blocks are quantum fields, and particles are ripples in them.
Why build a ring instead of a straight line? Show answer
The particles come round again, so the same accelerating section can give them a kick on every lap.
What sets the size of the ring? Show answer
The magnets. The bigger the tunnel, the weaker the magnets can be, and the collider used the strongest that could be built at the time.
Why does the collider need so many collisions? Show answer
Bunches of protons mostly pass through each other, and the interesting events are a tiny fraction of the collisions that do happen.
How many collisions happen each second, by Don Lincoln's count? Show answer
About 20 per crossing at 40 million crossings a second, roughly a billion collisions.
What do triggers do? Show answer
They decide 40 million times a second whether a crossing looks interesting, cutting the data to about 1,000 events a second kept for study.
What does Lincoln's top quark story show? Show answer
In 1995 his team had perhaps 19 top quarks after months of data. The newer collider may make one every second, thanks to higher energy and more collisions.
Why does Lincoln compare protons to garbage cans? Show answer
They are full of stuff, so a piece of one hits a piece of another and the outcome cannot be dialled in as with electrons.
How far away are the energies that would test a final theory? Show answer
About a quadrillion times beyond today's machines, according to Lincoln. Cliff says it would take an accelerator circling the Milky Way.
What is Lisa Randall's cautionary tale? Show answer
Confidence that the European collider would find supersymmetry helped leave it the only machine after the larger American one was cancelled, and supersymmetry has not appeared.
What is the alternative to building a bigger machine? Show answer
Higher precision. Cliff's experiment measures known particles carefully, looking for the footprints of something new.