Curated category
Concepts in astronomy
- Big BangThe Big Bang places the beginning of the universe at an estimated 13.787 billion years ago. That single number, drawn from detailed measurements of how fast…
- Black holeA black hole is so compact that its gravity stops everything, including light, from escaping. That boundary of no escape has a name: the event horizon.
- Cosmic inflationCosmic inflation is the idea that the universe, in its very first fractions of a second, expanded at a rate so extreme that distances between points doubled…
- Dark energyDark energy is the name scientists gave to whatever is pushing the universe apart at an ever-faster rate, and it makes up 68% of everything that exists.
- UniverseThe universe is all of space and time and their contents. That deceptively simple phrase hides a staggering reality: roughly 93 billion light-years of…
- Gravitational waveGravitational waves are ripples in the fabric of spacetime itself, and on the 14th of September 2015 at 09:50:45 GMT, two detectors sitting thousands of…
- CometA comet can stretch an arc of up to 30 degrees across the night sky, the span of sixty full Moons. That is what a comet looks like when it is close and…
- GalaxyA galaxy holds, on average, an estimated 100 million stars, each one orbiting a shared center of mass that none of them will ever reach.
- PlanetA planet is a large, rounded astronomical body, and for centuries the word meant something humble: a point of light that wandered.
- CosmogonyIn ancient Greece, thinkers developed a cosmogony focused on the origin of matter, space, and time. This transition from Chaos to Cosmos formed a form of…
- Light-yearA light-year is not a measure of time. That single misconception trips up almost everyone who hears the word for the first time, and it sits at the heart of…
- Interstellar mediumThe interstellar medium is the matter and radiation filling the vast space between star systems in a galaxy. Imagine the emptiness between stars not as a…
- Stellar nucleosynthesisStellar nucleosynthesis is the process by which stars forge the chemical elements that make up everything around us. Every atom of carbon in your body, every…
- StarA star is a luminous spheroid of plasma held together by self-gravity. The nearest one to Earth is the Sun. Look up on a clear night, and the other points of…
- Newton's law of universal gravitationNewton's law of universal gravitation begins with a deceptively simple claim: every particle in the universe attracts every other particle.
- Gravitational lensGravitational lensing is the bending of light by mass sitting between a distant source and an observer. On the 29th of May 1919, Arthur Eddington, Frank…