antimatter: Molecules formed by atoms consisting of antiprotons, antineutrons, and positrons.
Big Bang: The rapid expansion of dense matter and space-time that, according to current theory, marked the origin of the universe. It is supported by astronomers’ current understanding of the composition and structure of the universe.
black hole: A region of space having a gravitational field so intense that no matter or radiation (including light) can escape.
cosmos: (adj. cosmic) A term that refers to the universe and everything within it.
density: The measure of how condensed some object is, found by dividing its mass by its volume.
Hawking radiation: The particles emitted from the event horizon on the outer edges of a black hole. Energy can be converted into a pair of particles. If that happens very close to outer edge of a black hole, one of those particles can tunnel out and become detected — providing the only direct physical clue to the black hole’s presence. These emissions are called Hawking radiation for Stephen Hawking, the famous British physicist who came up with the idea that black holes can emit particles.
mass: A number that shows how much an object resists speeding up or slowing down — basically a measure of how much matter that object is made from.
matter: Something that occupies space and has mass. Anything on Earth with matter will have a property described as “weight.”
particle: A minute amount of something.
phenomenon: Something that is surprising or unusual.
physics: The scientific study of the nature and properties of matter and energy. Classical physics is an explanation of the nature and properties of matter and energy that relies on descriptions such as Newton’s laws of motion. Quantum physics, a field of study that emerged later, is a more accurate way of explaining the tiny motions and behavior of matter about the size of electrons. A scientist who works in such areas is known as a physicist.
planet: A large celestial object that orbits a star but unlike a star does not generate any visible light.
radiation: (in physics) One of the three major ways that energy is transferred. (The other two are conduction and convection.) In radiation, electromagnetic waves carry energy from one place to another. Unlike conduction and convection, which need material to help transfer the energy, radiation can transfer energy across empty space.
radioactive decay: A process by which an element is converted into a lighter element through the shedding of subatomic particles (and energy).
shock waves: Tiny regions in a gas or fluid where properties of the host material change dramatically owing to the passage of some object (which could be a plane in air or merely bubbles in water). Across a shock wave, a region’s pressure, temperature and density spike briefly, and almost instantaneously.
star: The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become hot enough, stars will emit light and other forms of electromagnetic radiation. The sun is our closest star.
summit: (in public policy) A meeting between officials of some organization or governments, often with the goal of negotiating new rules, policies or treaties.
universe: The entire cosmos: All things that exist throughout space and time. It has been expanding since its formation during an event known as the Big Bang, some 13.8 billion years ago (give or take a few hundred million years).