Astronomy flashcards
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30 decks
- Introduction (Astronomy)Recall cards introducing astronomy. What astronomy studies and where the elements of life were made. The nature of science: hypotheses, observational versus historical science, and peer review. The universality of physical laws. Numbers in astronomy: scientific notation, the speed of light, and the light-year. Light travel time and looking back in time. A tour of the solar system: planets, stars, the astronomical unit, and the sizes and distances of the Earth, Moon, and Sun. The Milky Way and the large-scale universe: galaxies, constellations, the Local Group, Andromeda, superclusters, and quasars. The universe of the very small: atoms, molecules, elements, and the density of matter in air, interstellar, and intergalactic space. Carl Sagan's cosmic calendar.
- Observing the Sky: The Birth of Astronomy (Astronomy)Recall cards on how humans learned to read and understand the sky. The celestial sphere and its landmarks: zenith, horizon, celestial poles and equator, and how the pole's altitude reveals your latitude. The ecliptic, the 88 constellations, asterisms, and the zodiac. Ancient astronomy: Eratosthenes measuring the Earth, Hipparchus and his star catalog, magnitudes, and precession, Ptolemy's geocentric model and the Almagest, Stonehenge, and the Maya. Astrology versus astronomy: horoscopes, the twelve signs, and why astrology has no scientific support. The birth of modern astronomy: Copernicus and the heliocentric model, and Galileo's telescopic discoveries of the phases of Venus, the moons of Jupiter, the stars of the Milky Way, and the mountains of the Moon.
- Orbits and Gravity (Astronomy)Recall cards on how the motions of the planets were measured and finally explained. Tycho Brahe's 20 years of observations and Kepler's three laws of planetary motion: elliptical orbits, foci and eccentricity, the law of equal areas, and P squared = a cubed. Newton's synthesis: his three laws of motion, momentum, mass, velocity, acceleration, density, and angular momentum. The universal law of gravitation, the inverse-square force, the gravitational constant, and Newton's mass-bearing form of Kepler's third law. Orbits in the solar system: perihelion and aphelion, the eight planets, the asteroid belt, and comets. Satellites and spacecraft: circular and escape speeds, orbital decay, and gravity assists (Voyager 2). Finally, gravity with many bodies: perturbations and the prediction and discovery of Neptune that confirmed Newton's laws.
- Earth, Moon, and Sky (Astronomy)Recall cards on how Earth's motions define the sky and our measures of time. The celestial sphere: great circles, meridians, longitude and latitude, the celestial equator and poles, declination and right ascension, and Foucault's pendulum. The seasons: Earth's 23.5-degree axial tilt, solstices and equinoxes, and the tropics and polar circles. Keeping time: sidereal versus solar days, apparent and mean solar time, standard time zones, daylight saving, and the International Date Line. The calendar: the tropical year and synodic month, the Julian and Gregorian reforms, and leap-year rules. Phases and motions of the Moon: the sidereal and synodic months, phase rise and set times, and synchronous rotation. Ocean tides: the tidal force, two bulges, spring and neap tides, and tidal friction. Finally eclipses of the Sun and Moon: umbra and penumbra, annular and total eclipses, and why they do not happen every month.
- Radiation and Spectra (Astronomy)Recall cards on light and how it reveals the nature of matter across the universe. The behavior of light: Maxwell's electromagnetic theory, wavelength and frequency, the speed of light, the photon and wave-particle duality, and the inverse square law of brightness. The electromagnetic spectrum: gamma rays, X-rays, ultraviolet, visible, infrared, microwaves, and radio waves, plus Wien's law and the Stefan-Boltzmann law for blackbody radiation. Spectroscopy: Newton's prism, dispersion, continuous, absorption, and emission spectra, Fraunhofer lines, and Kirchhoff's identification of elements. The structure of the atom: electrons, protons, and neutrons, the nucleus, isotopes, the Bohr model, and Planck's constant. Formation of spectral lines: ground and excited states, excitation and emission, the Lyman, Balmer, and Paschen series of hydrogen, ionization, and recombination. Finally the Doppler effect: blueshift and redshift, radial velocity, and the Doppler formula.
- Astronomical Instruments (Astronomy)Recall cards on the telescopes and detectors astronomers use to study the universe. Telescopes: their light-gathering and focusing functions, aperture and collecting area, refractors versus reflectors, chromatic aberration, the Newtonian and Cassegrain focus, and the history from Lippershey and Galileo to Newton's first reflector and the great refractors. Telescopes today: the 8-to-10-meter giants (Keck, Gran Telescopio Canarias, VLT, Subaru, Gemini, Hale), segmented mirrors, high and dark sites, and active and adaptive optics. Detectors: photographic plates, CCDs, imaging versus spectroscopy, diffraction gratings, and cooled infrared detectors. Radio telescopes: Jansky and Reber, dishes and receivers, Green Bank, Arecibo, and FAST, and interferometry from the VLA and ALMA to the VLBA. Space observatories: Hubble, IRAS, Spitzer, JWST, SOFIA, Chandra, and Fermi. And the future giants: the ELT, TMT, GMT, Vera Rubin Observatory, and the Cherenkov Telescope Array.
- The Solar System: An Overview (Astronomy)Recall cards introducing the solar system as a whole. Its inventory: the Sun, the eight planets, their moons and rings, and debris such as asteroids, comets, and dust, formed together about 4.5 billion years ago. The layout: the Sun holding 99.8 percent of the mass, the terrestrial versus jovian planets, distances in astronomical units and orbital periods, densities, and rotations. The smaller bodies: trans-Neptunian objects, the five dwarf planets, moons from the Galilean satellites to Titan and Triton, ring systems, asteroids, comets, meteors, and meteorites. Composition and structure: the hydrogen-rich giants, silicate-and-iron terrestrials, differentiation, and how surface temperature falls with distance. Dating surfaces by crater counts and by radioactive decay, with the major parent-daughter isotope pairs and their half-lives. And the origin of the solar system from a spinning solar nebula of gas and dust.
- Earth as a Planet (Astronomy)Recall cards studying Earth as one of the terrestrial planets. Its bulk properties: diameter, mass, record-high density, and escape velocity. Its layered interior built by differentiation: the basaltic oceanic and granitic continental crust, the deep mantle, the iron core, and the magnetic field and magnetosphere the liquid core produces. Its restless crust: igneous, sedimentary, and metamorphic rock, roughly a dozen tectonic plates driven by mantle convection, seafloor spreading, subduction, faults, continental drift, and hot spots. Its atmosphere: the nitrogen-oxygen-argon mix, sea-level pressure, the troposphere, stratosphere, and ionosphere, the ozone layer, and weather versus climate. The coevolution of life and air: the oldest rocks, stromatolites, the rise of oxygen, and present-day carbon dioxide and the greenhouse effect. And the cosmic impacts that have shaped Earth, from Tunguska and Chelyabinsk to Meteor Crater and the Chicxulub impact that ended the age of the dinosaurs.
- Cratered Worlds: The Moon and Mercury (Astronomy)Recall cards studying the Moon and Mercury, the airless, heavily cratered worlds closest to home. The Moon's bulk properties: its diameter, mass, surface gravity, escape velocity, low density, and synchronous rotation, and why it holds no atmosphere. Its two terrains: the dark basaltic maria that flooded impact basins, the bright, ancient, heavily cratered highlands of anorthosite, the regolith, and its extreme day and night temperatures. The physics of impact cratering: impact speeds, the nuclear-scale blast, crater and ejecta sizes, bright rays, secondary craters, and how often craters of a given size form. The competing ideas for the Moon's origin, from the fission, sister, and capture hypotheses to the leading giant impact hypothesis. And Mercury: its eccentric orbit, huge iron core, 3-to-2 spin-orbit resonance, temperature extremes, shrinkage scarps, the Caloris basin, polar ice, and the Mariner 10 and MESSENGER missions that mapped it.
- Earthlike Planets: Venus and Mars (Astronomy)Recall cards comparing Venus and Mars, Earth's two nearest planetary neighbors. The bulk and orbital data of each world: distance from the Sun, orbital period, diameter, mass, density, surface gravity, escape velocity, rotation, and surface conditions. The geology of Venus: its lowland lava plains, the absence of plate tectonics, the Aphrodite and Ishtar highlands, the Maxwell Mountains, its shield volcanoes and pancake domes, and how Magellan's radar and the Venera landers explored it. The crushing 90-bar, 96-percent carbon-dioxide atmosphere of Venus, its sulfuric-acid clouds, and the runaway greenhouse effect that makes it the hottest planet. The geology of Mars: Olympus Mons, the Valles Marineris canyons, the Tharsis bulge, its cratered southern highlands, and the Mariner and Viking missions. The evidence for water and life on Mars: its polar caps, runoff and outflow channels, recurring slope lineae, subsurface ice, and ancient lakebeds. And why three planets that began alike diverged into such different worlds.
- The Giant Planets (Astronomy)Recall cards on the four giant planets of the outer solar system: Jupiter, Saturn, Uranus, and Neptune. The composition of the outer solar system and the distinction between the gas giants (Jupiter and Saturn) and the ice giants (Uranus and Neptune). The robotic missions that explored them: the Pioneers, the two Voyagers and their Grand Tour, Galileo and its atmospheric probe at Jupiter, Cassini and the Titan landing at Saturn, and Juno's polar orbit. The bulk properties of each planet: orbital period, diameter, mass, density, rotation, and axial tilt, including Uranus tipped on its side. Their interiors of liquid metallic hydrogen, rock-and-ice cores, internal heat sources, and strong tilted magnetic fields. And their atmospheres: the hydrogen-helium composition, the ammonia and methane cloud decks, the belts and zones, the ferocious jet streams, and the long-lived storms such as Jupiter's Great Red Spot and Neptune's Great Dark Spot.
- Rings, Moons, and Pluto (Astronomy)Recall cards on the moon and ring systems of the giant planets, and on the dwarf planet Pluto. The four Galilean moons of Jupiter: heavily cratered Callisto, giant Ganymede, ocean-bearing Europa, and volcanic Io, whose eruptions are driven by tidal heating. Saturn's moons, including Titan with its thick nitrogen atmosphere and hydrocarbon lakes, and Enceladus with its water geysers and subsurface ocean. Neptune's captured moon Triton, the coldest world yet visited, with its nitrogen geysers. Pluto and its large moon Charon, in a double tidal lock, explored by New Horizons in 2015. And the planetary ring systems: the bright, broad water-ice rings of Saturn with the Cassini Division, the dark narrow rings of Uranus and Neptune, and how orbital resonances and shepherd moons sculpt them.
- Comets and Asteroids (Astronomy)Recall cards on the small bodies of the solar system: asteroids and comets. The asteroid belt between Mars and Jupiter, the largest asteroids Ceres, Pallas, and Vesta, and the C-type, S-type, and M-type compositional classes. The spacecraft that visited and sampled asteroids: Galileo, NEAR-Shoemaker, Hayabusa, OSIRIS-REx, Dawn, and Lucy, plus the interstellar visitor 'Oumuamua. Near-Earth objects and planetary defense: the Tunguska and Chelyabinsk airbursts, the Spaceguard Survey, and the DART and Hera missions. The anatomy of a comet, its nucleus, coma, and tails, Fred Whipple's dirty snowball model, and famous comets such as Halley and 67P Churyumov-Gerasimenko explored by Rosetta and Philae. And the reservoirs that supply comets: the distant Oort cloud of long-period comets and the Kuiper belt beyond Neptune that feeds the short-period comets.
- Cosmic Samples and the Origin of the Solar System (Astronomy)Recall cards on the cosmic samples that reach Earth and what they reveal about how the solar system formed. Meteors, the shooting stars produced when tiny particles burn up in the atmosphere, and the meteor showers Earth meets when it crosses a comet's debris stream, from the Perseids to the Leonids. Meteorites, the fragments that survive to the ground: the iron, stony, and stony-iron classes, primitive versus differentiated bodies, and the amino acids in the Murchison meteorite that date the solar system to about 4.56 billion years. The solar nebula model of formation: a collapsing spinning disk, the condensation sequence that split the rocky inner planets from the icy giants, planetesimal accretion, and differentiation. What other planetary systems teach us, found by the Doppler and transit methods and by Kepler: super-Earths, hot Jupiters, and planetary migration. And the long-term evolution of worlds, where size governs how long a planet stays geologically alive, from the dead Moon to plate-tectonic Earth and Olympus Mons on Mars.
- The Sun: A Garden-Variety Star (Astronomy)Recall cards on the Sun, the ordinary star at the center of our solar system, and the activity that plays across its surface. Its structure and composition: a ball of mostly hydrogen and helium a million kilometers wide, from the 15-million-degree core out through the convective zone to the visible photosphere, the thin chromosphere, and the tenuous but million-degree corona that launches the solar wind. The solar cycle: sunspots and their umbra and penumbra, the roughly 11-year rhythm of sunspot maxima, differential rotation, the Zeeman effect that maps magnetic fields, and the 22-year magnetic cycle driven by the solar dynamo. Solar activity above the photosphere: plages, prominences, flares, coronal mass ejections, and the active regions where strong magnetic fields tie them together. And space weather, the way particles and radiation from the Sun disturb Earth's magnetosphere, from the Carrington Event of 1859 and the 1989 Quebec blackout to the Maunder Minimum.
- The Sun: A Nuclear Powerhouse (Astronomy)Recall cards on how the Sun actually shines. The nineteenth-century puzzle of the Sun's energy source: chemical burning would last only a few thousand years, and even Kelvin and Helmholtz's gravitational contraction could power it for only about 100 million years, far short of Earth's geological age. The answer came from Einstein's E = mc^2 and nuclear fusion: deep in the core, above about 12 million K, the proton-proton chain fuses roughly 600 million tons of hydrogen into helium each second, converting about 4 million tons of matter into pure energy. The solar interior in theory: hydrostatic equilibrium, the radiative and convective zones, and the hundreds of thousands of years a photon takes to escape while a neutrino leaves in seconds. And the observations that confirm it: the solar neutrino problem, neutrino oscillation, the Davis and Sudbury experiments, and helioseismology.
- Analyzing Starlight (Astronomy)Recall cards on how astronomers read a star's light. Brightness: the difference between luminosity (total energy emitted per second) and apparent brightness (energy reaching us), the inverse-square dimming with distance, and Hipparchus's magnitude scale on which brighter means a smaller number and five magnitudes span a factor of 100. Color: a star's surface temperature sets its color, from over 40,000 K blue-white down to about 2,000 K red, quantified by the UBV color index. Spectra: the temperature-ordered OBAFGKM (plus L, T, Y) classes, their spectral-line signatures, brown dwarfs, and Annie Jump Cannon. And what spectra reveal: composition (about three-quarters hydrogen), radial velocity from the Doppler shift, proper motion across the sky, and rotation and pressure read from the width of the lines.
- The Stars: A Celestial Census (Astronomy)Recall cards on taking a census of the stars. The solar neighborhood: counting the stars within about 21 light-years shows that cool, faint red M dwarfs vastly outnumber luminous stars, and that the bright stars in our sky are bright because they are powerful, not because they are near. Masses: how binary stars and Newton's form of Kepler's third law let astronomers weigh stars, from the smallest true stars near 1/12 of a solar mass, through brown dwarfs, up to about 250 solar masses, and the mass-luminosity relation linking the two. Diameters: the indirect methods (lunar occultations, eclipsing binaries, and the Stefan-Boltzmann law) that reveal sizes from roughly Sun-sized up to the vast red supergiant Betelgeuse. And the Hertzsprung-Russell diagram: the plot of luminosity against temperature on which the main sequence, giants, supergiants, and white dwarfs each take their place.
- Celestial Distances (Astronomy)Recall cards on how astronomers measure distances in space. Fundamental units: the history of the meter, the light-second, and the astronomical unit (the average Earth-Sun distance), pinned down in modern times by radar ranging. Surveying the stars: parallax and triangulation, the parsec, the relation D = 1/p, the first stellar parallax measured by Bessel in 1838, and the Hipparcos and Gaia satellites that extended the method across the Galaxy. Variable stars as standard candles: pulsating cepheids and RR Lyrae stars, the light curve and period, and Henrietta Leavitt's period-luminosity relation that let cepheids reach tens of millions of light-years. And the H-R diagram method (spectroscopic parallax), the luminosity classes from supergiants to dwarfs, and the cosmic distance ladder that chains all these techniques together.
- Between the Stars: Gas and Dust in Space (Astronomy)Recall cards on the interstellar medium, the gas and dust between the stars. The mix: about 99% gas and 1% dust, mostly hydrogen and helium, totaling roughly 15% of the Galaxy's stellar mass. Interstellar gas: hot ionized H II regions and their red H-alpha glow, cool neutral hydrogen and the 21-centimeter line, ultra-hot supernova gas, and cold giant molecular clouds rich in molecules. Cosmic dust: tiny grains with rocky cores and icy mantles that cause extinction, reddening, and reflection and dark nebulae. Cosmic rays: high-speed nuclei and electrons, mostly protons, arriving near light speed. The life cycle of cosmic material as stars return enriched gas and dust to space. And the Sun's own neighborhood, the hot Local Bubble and the Local Fluff cloud around us.
- The Birth of Stars and the Discovery of Planets outside the Solar System (Astronomy)Recall cards on how stars are born and how we find planets around other stars. Star formation in giant molecular clouds: their cold, filamentary interiors, the dense clumps and cores that collapse, and the vivid example of the Orion molecular cloud and its nebula. The stages of a forming star: protostars, whirling protostellar disks, T Tauri stars, stellar winds, and the jets that light up Herbig-Haro objects. Reading stellar evolution off the H-R diagram: evolutionary tracks, the 12-million-K threshold for reaching the main sequence, and the mass limits of true stars. Evidence that planets form in circumstellar disks, growing by accretion from dust grains to planetesimals to giant planets. And the exoplanet revolution: 51 Pegasi b, the radial-velocity and transit methods, direct imaging, Kepler's harvest, super-Earths and mini-Neptunes, and planetary migration.
- Stars from Adolescence to Old Age (Astronomy)Recall cards on how stars age and die. Life on the main sequence: the zero-age main sequence, the small fraction of mass turned into energy by fusion, and how sharply lifetime depends on mass, from an O star lasting a million years to an M dwarf lasting hundreds of billions. The path off the main sequence: core contraction, shell hydrogen fusion, and the swelling into a cool, luminous red giant like Betelgeuse. Reading stellar ages off star clusters: the globular, open, and association types, and the main-sequence turnoff that dates a cluster and even limits the age of the universe. And the later stages: the triple-alpha process and helium flash, the layered carbon-oxygen core, the ejection of a planetary nebula, and, for massive stars, fusion up an onion-shell structure that ends at iron.
- The Death of Stars (Astronomy)Recall cards on how stars end their lives. Low-mass deaths: the Chandrasekhar limit, electron-degenerate white dwarfs, their carbon-oxygen-neon composition and extreme density, and their fade to black dwarfs. The explosive finish of massive stars: the onion-shell interior fusing up to iron, core collapse into neutrons and neutrinos, and the type II supernova that seeds space with the heaviest elements. Observed supernovae from SN 1006 to SN 1987A. Neutron stars and pulsars: their size, density, and surface gravity, Jocelyn Bell's 1967 discovery, the lighthouse model, and magnetars. Binary evolution: novae, type Ia supernovae, and millisecond pulsars. And the gamma-ray bursts, short from merging neutron stars and long from collapsing massive stars.
- Black Holes and Curved Spacetime (Astronomy)Recall cards on Einstein's general relativity and its most extreme prediction. The theory itself: the equivalence principle, spacetime curved by matter, and gravity as that curvature. The classic tests: Mercury's perihelion precession, the 1919 eclipse deflection of starlight, gravitational redshift and time dilation, and the relativistic corrections that keep GPS accurate. Black holes: the event horizon, the Schwarzschild radius, the singularity, spaghettification, and the core mass needed to form one. The evidence: X-ray binaries, accretion disks, Cygnus X-1, and the supermassive black holes at galactic centers. And gravitational-wave astronomy: the binary pulsar PSR 1913+16, LIGO, and the 2015 black-hole and 2017 neutron-star mergers.
- The Milky Way Galaxy (Astronomy)Recall cards on our home galaxy. Its architecture: Herschel's and Shapley's mapping, the thin and thick disk, the nuclear bulge, and the stellar and dark-matter halo, with the Sun's place about 26,000 light-years from the center. Its spiral structure traced by the 21-cm hydrogen line, the Scutum-Centaurus and Perseus arms, and the Sun's Orion-Cygnus spur. Its mass from orbital speeds and Kepler's third law, the 225-million-year galactic year, and the evidence for a vast dark halo. Its center: the 4.6-million-solar-mass black hole Sagittarius A*, the stellar orbits that weigh it, and Andrea Ghez's Nobel-winning work. Its stellar populations: Baade's Population I and II and their ages and metallicities. And its formation and growth by protogalactic collapse and the ongoing accretion of dwarf galaxies, ending with the coming Andromeda merger.
- Galaxies (Astronomy)Recall cards on galaxies beyond the Milky Way. Their discovery: Kant's island universes, the great debate over the spiral nebulae, and Edwin Hubble's 1924 proof, using cepheids in Andromeda, that galaxies lie far beyond our own. Their types on Hubble's tuning-fork diagram: Sa to Sc spirals and barred spirals, E0 to E7 ellipticals from dwarfs to giants, S0 lenticulars, and irregulars like the Magellanic Clouds, with their sizes, masses, and luminosities. Their properties measured from rotation and orbital speeds, and the mass-to-light ratios that betray dark matter. The extragalactic distance ladder: cepheids, type Ia supernovae, and the Tully-Fisher relation. And the expanding universe: Slipher's redshifts, Lemaitre's 1927 theory, the Hubble-Humason velocity-distance law, the Hubble constant, and the raisin-bread picture of expansion with no center.
- Active Galaxies, Quasars, and Supermassive Black Holes (Astronomy)Recall cards on active galactic nuclei and the supermassive black holes that power them. Quasars: the meaning of quasi-stellar radio source, their 1950s discovery with surplus radar gear, Maarten Schmidt's 1963 reading of the huge redshift of 3C 273, the redshifts that reach 96% of the speed of light, the Hubble Space Telescope host galaxies, and the rapid variability that pins the emitting region to a few light-months. The engine: a central black hole fed by a friction-heated accretion disk, the roughly 10% mass-energy efficiency that dwarfs nuclear fusion, masses from under a million to tens of billions of Suns, M87 and the 2019 Event Horizon Telescope shadow, and jets launched near light speed. And cosmic evolution: the early peak of quasars and star formation, the 1/200 black-hole-to-galaxy mass ratio, tidal disruption events, seed black holes, mergers such as NGC 6240, and black-hole feedback on star birth.
- The Evolution and Distribution of Galaxies (Astronomy)Recall cards on how galaxies formed, grew, and arranged themselves across the cosmos. Looking back in time: the 13.8-billion-year-old universe, the first stars within a billion years, the more than 2 trillion galaxies, and the tiny, blue, low-mass early galaxies seen at high redshift. Galaxy mergers: collisions far more common in the past, starbursts that burn through their gas in a few million years, the Tadpole and its tidal tail, NGC 6240's twin black holes, and galactic cannibalism. Large-scale structure: the cosmological principle, the Local Group, the Virgo and Coma clusters, superclusters, voids, and the sponge-like cosmic web. Dark matter: galaxy rotation curves, cluster mass-to-light ratios, gravitational lensing, MACHOs, and cold versus hot dark matter. And the assembly of structure: top-down versus bottom-up formation, red-and-dead ellipticals, and a universe that is about 5% atoms, 27% dark matter, and 68% dark energy.
- The Big Bang (Astronomy)Recall cards on the origin and evolution of the whole universe. The age of the cosmos: the Hubble time, the 13.8-billion-year-old universe, the deceleration that gave way to dark-energy acceleration, and the 1998 Type Ia supernova result honored with the 2011 Nobel Prize. A model of the universe: the homogeneous and isotropic large-scale cosmos, the scale factor, cosmological redshift, critical density, and open, closed, and flat geometries. The beginning: the Big Bang, Lemaitre's primeval atom, Gamow's hot early universe, the temperature-time ladder, and the nucleosynthesis of hydrogen, helium, and lithium in the first four minutes. The cosmic microwave background: Penzias and Wilson, the 2.73-kelvin blackbody, recombination at 380,000 years, and the COBE, WMAP, and Planck missions. What the universe is made of: about 4% ordinary matter, 27% dark matter, and 68% dark energy. And the frontier ideas: inflation and the flatness and horizon problems, the four fundamental forces, grand unified theories, the anthropic principle, cosmic fine-tuning, and the multiverse.
- Life in the Universe (Astronomy)Recall cards on the search for life beyond Earth. The cosmic context: the chemical evolution of the elements, organic molecules and hydrocarbons, biochemistry, and Earth as the third planet with liquid water. Astrobiology: the elements and solvent life requires, extremophiles and the known limits of temperature, acidity, and alkalinity, the earliest fossils and stromatolites, the rise of oxygen, proteins and DNA, the RNA world, and the Miller-Urey experiments. Searching the solar system and beyond: the habitable zone, the Viking, Curiosity, and Perseverance missions to Mars, the subsurface oceans of Europa and Enceladus, the hydrocarbon lakes and tholins of Titan, the first exoplanet, and atmospheric biosignatures. And the search for extraterrestrial intelligence: the Drake equation, why radio waves are favored, Project Ozma, the Allen Telescope Array, Arecibo, FAST, and Breakthrough Listen.