(Every day until Christmas, I’ll be posting a science-related image.)

Day 17

Our bodies are made of atoms—hydrogen, carbon, oxygen, nitrogen, phosphorous, calcium, iron, and so forth. Those atoms, in their turn, are made of electrons, protons, and neutrons. Electrons appear to be fundamental: no experiment has shown signs they consist of more primitive particles. However, protons and neutrons are the most stable examples of hadrons, particles made up of quarks bound together by gluons. Quarks are (again, as far as we can tell) fundamental, indivisible particles, while gluons are mediators of force.

Probing matter at its most fundamental requires high energies. We can’t see these particles, even with powerful microscopes: the wavelengths of visible light are much bigger than atoms, so we’ll never see them directly. To get to the constituents of atoms, one of the best ways is to collide particles together and measure what comes out. At sufficiently high energies, if protons collide with each other, they interact on the level of their constituent quarks and gluons. The (unfortunately) now-inoperative Tevatron collider at Fermilab slammed streams of protons and their antiparticle partners, antiprotons, into each other at a high fraction of the speed of light. The huge Collider Detector at Fermilab (CDF) shown above is one of two Tevatron detectors that measured the energy and momentum of particles produced in these high-energy collisions, sifting through the vast number of byproducts to find new particles, new interactions, and ultimately get at the structure of matter at its most basic. CDF and its fellow Tevatron detector DØ (pronounced “D-zero”) found the top quark, the heaviest and most unstable of the quarks; they also contributed to the discovery of the Higgs boson.

Sometimes to comprehend the very small, we need to construct very large devices.