G

is for galaxies—see how they turn!

Galaxies are huge collections of stars, all held together by gravity. By some estimates, the Milky Way galaxy contains up to 400 billion stars, and scientists estimate that our universe holds at least 100 billion galaxies. Researchers study the behavior of galaxies to learn more about the invisible things that influence them, such as dark matter and dark energy.

H

is for Higgs, discovered at CERN.

The Higgs field gives many fundamental particles their mass. Theorists predicted the existence of the Higgs boson in the 1960s, but they didn’t know what mass the Higgs boson itself might have, making it very difficult to find. After five decades of searching, experimentalists finally discovered the Higgs boson at the Large Hadron Collider in 2012.

I

is for inflation that made the universe

expand.

Imagine if things the size of an atom suddenly expanded to the size of a grapefruit. That’s what scientists believe happened during inflation, a short but violent period early in the universe’s history. The universe grew, stretching minor quantum variations into larger patterns that can still be read in the sky in light left over from just after the big bang.

J

A joule is the name for a certain amount of energy. It’s roughly equivalent to you lifting a small apple a meter in the air. One of the most energetic cosmic ray particles ever detected clocked in around 50 joules, which might seem unimpressive—until you compare the size of your arm to the size of a subatomic particle! This cosmic ray, propelled by an unknown source in space, was millions of times as energetic as the particles accelerated at the Large Hadron Collider, the most powerful accelerator ever built.

is for Joule,

a measurement of energy on hand.

K

Many subatomic particles are made of building blocks called quarks, which come in six different types. Kaons are particles that contain a quark called a strange quark. Kaons are important because scientists used them to find clues as to why our universe is made of more matter than antimatter. They discovered that kaons and their antimatter partners decay in different ways, contributing to the imbalance.

is for kaons,

with quarks that are strange.

L

is for leptons, which have a wide range.

The leptons are a family of subatomic particles. The best-known lepton is the electron. Other leptons include heavier versions of the electron called muon and tau particles, and a group of three almost massless particles called neutrinos. Unlike some other particles, leptons don’t combine with one another; they like their personal space.