Curated playlist
Concepts in astronomy
- Big BangThe name Big Bang began as a passing remark on the BBC. Fred Hoyle, who favored a rival theory, coined it in 1949.
- Black holeEinstein used his own theory in 1939 to argue black holes were impossible. Decades later, astronomers photographed one.
- Cosmic inflationCosmic inflation says a region smaller than an atom ballooned to roughly the size of a grapefruit.
- Dark energyDark energy makes up 68% of everything, yet nobody knows what it is. It pushes the universe apart faster.
- UniverseIn 1998, two research groups found the universe's expansion is speeding up.
- Gravitational waveA gravitational wave from two black holes stretched a four-kilometer detector arm by a thousandth of a proton's width.
- QuasarA quasar named 3C 273, in the constellation of Virgo, is the brightest of its kind in Earth's sky. Quasars are extremely luminous cores of distant galaxies, and this one offers a way to feel their scale. Move 3C 273 to a distance of about…
- Stellar classificationThe Sun carries a short label that astronomers write as G2V. Those three characters say it is a main-sequence star with a surface temperature of around 5,800 K. Nearly every star whose light can be studied receives a code like it. The…
- CometA close, bright comet can stretch up to 30 degrees across the sky, the span of sixty full Moons.
- GalaxyIn a typical galaxy, most of the mass is dark matter, not stars. Only a few percent shows up as stars and nebulae.
- PlanetFor centuries, Earth was not counted as a planet. The word first meant a wandering point of light.
- CosmogonyThe Big Bang model cannot actually reach the moment of the beginning.
- Light-yearA light-year is not a measure of time. It is a distance, roughly 9.46 trillion kilometers.
- ParsecThe parsec is an astronomer's unit of length, and the nearest star, Proxima Centauri, sits about 1.3 of them from the Sun. Seen from that star, the whole gap between Earth and the Sun would look slightly less than one arcsecond wide. That…
- Interstellar mediumVoyager 1 crossed into interstellar space on the 25th of August 2012. Voyager 2 followed on the 5th of November 2018.
- Stellar nucleosynthesisEvery carbon atom in your body was made inside a star. Stellar nucleosynthesis explains how stars forge elements.
- StarOnly about 4,000 stars are visible to the naked eye, and every one is in the Milky Way.
- Newton's law of universal gravitationNewton called gravity's pull across empty space "so great an absurdity". He wrote it in 1692.
- Gravitational lensIn 1919, a solar eclipse showed stars in the wrong places. Bent light backed Einstein's theory.
- Dark matterDark matter, added up from the Sun out to the orbit of Neptune, would weigh about as much as a large asteroid. That is a strikingly small amount. Yet across the universe as a whole, dark matter makes up roughly 85% of all mass. It does not…
- ConstellationA constellation is a patch of the celestial sphere where visible stars form a perceived outline, usually an animal, a mythological figure or an everyday object. Consider Orion and Scorpius. In myth, the scorpion assassinates the hunter,…