## Annihilation

When corresponding particles of matter and antimatter (for example, an electron and a positron) contact each other, they annihilate each other, converting their masses into energy in the form of high-energy photons. The total energy produced can be calculated by using the equation $E = mc^2$.

## Antimatter

Every particle of matter in the Standard Model has a corresponding particle of antimatter. Anti-particles can be thought of as equal and opposite “reflections” of their matter counterparts. Matter and antimatter can annihilate with each other, producing large amounts of energy. Surprisingly, matter and antimatter are not exact reflections of each other; there are some slight asymmetries between them.

## Big Bang

Cosmologists believe that the universe started much smaller than it is now — a nearly infinitesimal point. The unfathomably rapid expansion during the first moments of our universe’s existence is called the Big Bang.

## Big Crunch

According to the Big Crunch theory for the ultimate end of the universe, the expansion of the universe will reverse, leading to a massive collapse. This would effectively be like an inverted Big Bang.

## Big Freeze

A likely outcome for our universe is that as stars continue to die, the universe will slowly cool down, eventually decaying into a cloud of particles. This cosmological outcome is called the Big Freeze.

## Big Rip

A dramatic theory for the end of the universe, called the Big Rip, predicts that the universe will expand at an ever increasing rate. This would cause every atom in the universe to be violently torn apart.

## Black Hole

One fascinating consequence of General Relativity is the fact that some objects have such intense gravity that nothing can escape them — not even light! These extraordinary occurrences are called black holes. The extreme warping of spacetime around black holes leads to some bizarre phenomena.

## Boson

Bosons are the fundamental particles responsible for mediating the interactions (forces) between the fermions. They include the photon, gluon, and weak bosons, as well as the Higgs boson. Some physicists have speculated the existence of the graviton; however, it is unknown if such a particle exists.

## Cosmic Microwave Background Radiation (CMBR)

Telescopes that are sensitive to electromagnetic radiation in the microwave range can detect a faint signal from all directions in outer space. This signal, called the Cosmic Microwave Background Radiation (or CMBR for short), is a faint remnant from the early history of the universe. It is significant evidence for the Big Bang.

## Cosmology

Cosmology is a field of physics devoted to understanding questions about the large-scale structure and evolution of the universe. The generally accepted theory for the origin of the universe is the Big Bang. Three possible outcomes for the future of the universe are the Big Crunch, the Big Rip, and the Big Freeze. Cosmology also encompasses the study of dark matter and dark energy.