# Learn

> Guided lessons that teach orbits, the night sky, and our living planet on top of SpaceSphere's live data.

Canonical: https://spacesphere.sygnito.com/en/learn

Short lessons taught on live data. Each one explains an idea, checks your understanding, and ends in the real product.

Lessons open inside the Learn page. Progress, reviews and XP are kept in the visitor's own browser or account and are not part of this file.

## Beginner (600 lessons)

- Lesson 1: Orbits 101 (5 min)
- Lesson 2: Why can't you feel the Earth spinning? (4 min)
- Lesson 3: Where does space begin? (4 min)
- Lesson 4: How is the Solar System built? (4 min)
- Lesson 5: What is a satellite, and what does it do for you? (4 min)
- Lesson 6: Why can you see the Moon in the daytime? (4 min)
- Lesson 7: Why do we have seasons? (4 min)
- Lesson 8: Kinds of orbits: polar and sun-synchronous (4 min)
- Lesson 9: The ISS: a home in orbit (4 min)
- Lesson 10: The celestial sphere: why the sky turns (4 min)
- Lesson 11: Constellations: a map made of imagination (4 min)
- Lesson 12: How bright, how far. Reading the stars (4 min)
- Lesson 13: How rockets reach orbit (4 min)
- Lesson 14: Where rockets launch from (4 min)
- Lesson 15: Coming back down: reentry and space junk (4 min)
- Lesson 16: The living pulse of Earth (4 min)
- Lesson 17: Earthquakes: reading a shaking planet (4 min)
- Lesson 18: The Moon up close (4 min)
- Lesson 19: Moon phases: why the Moon changes shape (4 min)
- Lesson 20: Space weather: when the Sun sneezes (4 min)
- Lesson 21: What happens to a human in space without a spacesuit? (4 min)
- Lesson 22: Does a black hole suck everything in? (4 min)
- Lesson 23: Can you see the Great Wall of China from space? (4 min)
- Lesson 24: Where does the weather forecast come from? (4 min)
- Lesson 25: Why do stars twinkle when planets do not? (4 min)
- Lesson 26: What is a shooting star? (4 min)
- Lesson 27: Is Saturn the only planet with rings? (4 min)
- Lesson 28: What is the pale band of the Milky Way in the sky? (4 min)
- Lesson 29: Why is the sky blue and the sunset red? (4 min)
- Lesson 30: How many stars can you really see? (4 min)
- Lesson 31: Is the Sun on fire? (4 min)
- Lesson 32: Why is Pluto no longer a planet? (4 min)
- Lesson 33: Why is Mars red? (4 min)
- Lesson 34: Is the asteroid belt a crowded field of rocks? (4 min)
- Lesson 35: What is a comet, and where does its tail point? (4 min)
- Lesson 36: Do the planets ever line up in a row? (4 min)
- Lesson 37: Why does the Moon look huge near the horizon? (4 min)
- Lesson 38: Why is the Moon covered in craters while Earth has so few? (4 min)
- Lesson 39: Why do hurricanes spin opposite ways in the two hemispheres? (4 min)
- Lesson 40: Can you hear an explosion in space? (4 min)
- Lesson 41: Why is Venus hotter than Mercury? (4 min)
- Lesson 42: Why does the Apollo flag look like it is waving? (4 min)
- Lesson 43: What colour are the stars? (4 min)
- Lesson 44: Is Jupiter a failed star? (4 min)
- Lesson 45: Is Earth a perfect sphere? (4 min)
- Lesson 46: Where does Earth erupt the most? (4 min)
- Lesson 47: Is there such a thing as earthquake weather? (4 min)
- Lesson 48: Do astronauts grow taller in space? (4 min)
- Lesson 49: Is there water on Mars? (4 min)
- Lesson 50: Will the Sun explode as a supernova? (4 min)
- Lesson 51: Could Saturn float in water? (4 min)
- Lesson 52: Why is the Moon's sky black in the daytime? (4 min)
- Lesson 53: Is the Moon hot or cold? (4 min)
- Lesson 54: Does a compass point to the North Pole? (4 min)
- Lesson 55: Does lightning never strike the same place twice? (4 min)
- Lesson 56: Could you stop a hurricane with a bomb? (4 min)
- Lesson 57: Hurricane, typhoon or cyclone: what is the difference? (4 min)
- Lesson 58: Does every planet have a moon? (4 min)
- Lesson 59: Is the evening star really a star? (4 min)
- Lesson 60: Are sunglasses enough to look at the Sun? (4 min)
- Lesson 61: Is the North Star the brightest star? (4 min)
- Lesson 62: Are the stars you see already dead? (4 min)
- Lesson 63: Is the Sun a big star? (4 min)
- Lesson 64: Is Earth's centre hotter than the Sun's surface? (4 min)
- Lesson 65: Are the northern lights only in the north? (4 min)
- Lesson 66: Will Mars ever look as big as the Moon? (4 min)
- Lesson 67: Is there a face on Mars? (4 min)
- Lesson 68: Does Earth ever get a second moon? (4 min)
- Lesson 69: Can a telescope see the Apollo landing sites? (4 min)
- Lesson 70: Is a blue moon blue? (4 min)
- Lesson 71: Is there no gravity in space? (4 min)
- Lesson 72: How many satellites are working above you? (4 min)
- Lesson 73: Is the ozone hole still growing? (4 min)
- Lesson 74: Have we found another Earth? (4 min)
- Lesson 75: Can a solar eclipse poison your food? (4 min)
- Lesson 76: Does Saturn really have a hexagon? (4 min)
- Lesson 77: How fast does a Mars rover drive? (4 min)
- Lesson 78: Is Mercury the easiest planet to reach? (4 min)
- Lesson 79: Did Artemis II land on the Moon? (4 min)
- Lesson 80: Are the dark patches on the Moon seas? (4 min)
- Lesson 81: Can the ground swallow you in an earthquake? (4 min)
- Lesson 82: Is a tsunami one giant wave? (4 min)
- Lesson 83: Is the garbage patch a floating island? (4 min)
- Lesson 84: Do rainforests make most of our oxygen? (4 min)
- Lesson 85: Is lightning hotter than the Sun? (4 min)
- Lesson 86: Can astronauts cry in space? (4 min)
- Lesson 87: Can you buy a star and name it? (4 min)
- Lesson 88: Is a light-year a measure of time? (4 min)
- Lesson 89: Is the farthest planet the coldest? (4 min)
- Lesson 90: Where is the tallest volcano? (4 min)
- Lesson 91: Where are the fastest winds? (4 min)
- Lesson 92: Is the Moon shrinking? (4 min)
- Lesson 93: Could you jump higher on the Moon? (4 min)
- Lesson 94: How many people have walked on the Moon? (4 min)
- Lesson 95: Will the footprints on the Moon last? (4 min)
- Lesson 96: How big is the Moon? (4 min)
- Lesson 97: Could you drive to the Moon? (4 min)
- Lesson 98: Are rockets thrown away after one flight? (4 min)
- Lesson 99: Was Laika the first animal in space? (4 min)
- Lesson 100: Does the Sun stand still? (4 min)
- Lesson 101: What are Phobos and Deimos? (4 min)
- Lesson 102: How did Galileo find Jupiter's big moons? (5 min)
- Lesson 103: Europa, Ganymede and Callisto: three icy worlds (5 min)
- Lesson 104: Titan, Enceladus and the odd moons of Saturn (5 min)
- Lesson 105: Triton, Miranda and Charon: moons at the edge (5 min)
- Lesson 106: What makes a moon a moon? (4 min)
- Lesson 107: What happens when a comet nears the Sun? (4 min)
- Lesson 108: Where do the Solar System's small bodies live? (4 min)
- Lesson 109: Can astronauts fix any broken satellite? (4 min)
- Lesson 110: Is the ISS the only space station? (4 min)
- Lesson 111: Is every fireball a rock from space? (4 min)
- Lesson 112: Are the strongest hurricanes now Category 6? (4 min)
- Lesson 113: Is El Niño a storm? (4 min)
- Lesson 114: Are earthquakes becoming more common? (4 min)
- Lesson 115: Do the constellations always look the same? (4 min)
- Lesson 116: Can the Moon hide a planet? (4 min)
- Lesson 117: Is a strange moving light in the sky a UFO? (4 min)
- Lesson 118: Does the aurora look as colourful to the eye as in photos? (4 min)
- Lesson 119: Can there be ice on Mercury? (4 min)
- Lesson 120: Is every asteroid one solid rock? (4 min)
- Lesson 121: Is the asteroid Psyche a ball of gold? (4 min)
- Lesson 122: Does Halley's Comet come back every year? (4 min)
- Lesson 123: Is the Moon white? (4 min)
- Lesson 124: Does a crash on the Moon make only a short thud? (4 min)
- Lesson 125: Do heavy things fall faster? (4 min)
- Lesson 126: Do we only send radio signals into space? (4 min)
- Lesson 127: Does a trip to Mars take a few weeks? (4 min)
- Lesson 128: Does NASA launch the most rockets? (4 min)
- Lesson 129: Do astronauts drink recycled water? (4 min)
- Lesson 130: Were the Starliner astronauts stranded? (4 min)
- Lesson 131: Does it take days to reach the space station? (4 min)
- Lesson 132: Does melting sea ice raise the sea? (4 min)
- Lesson 133: Is the Sun causing today's warming? (4 min)
- Lesson 134: Can you watch a fault move? (4 min)
- Lesson 135: Is a meteorite hot when it lands? (4 min)
- Lesson 136: Is the universe as wide as it is old? (4 min)
- Lesson 137: Is Betelgeuse a single star? (4 min)
- Lesson 138: Is a nova a newborn star? (4 min)
- Lesson 139: Has anyone seen the Sun's poles? (4 min)
- Lesson 140: Is a solar flare the same as a CME? (4 min)
- Lesson 141: Will Saturn lose its rings? (4 min)
- Lesson 142: Has anything landed on the Moon since Apollo? (4 min)
- Lesson 143: Will the 2027 eclipse be the longest ever? (4 min)
- Lesson 144: Can everyone see a lunar eclipse? (4 min)
- Lesson 145: Are there trees on Earth that went to the Moon? (4 min)
- Lesson 146: Does a rocket take hours to reach orbit? (4 min)
- Lesson 147: What is the fastest thing people have built? (4 min)
- Lesson 148: Do rockets only launch from land? (4 min)
- Lesson 149: Did a probe built for Venus fall back to Earth? (4 min)
- Lesson 150: Why does radio go quiet when a capsule comes home? (4 min)
- Lesson 151: Is lava the deadliest part of a volcano? (4 min)
- Lesson 152: Is the North Pole on land? (4 min)
- Lesson 153: Is Earth's magnetic field about to flip? (4 min)
- Lesson 154: Can a wildfire make its own weather? (4 min)
- Lesson 155: Does the Sun always rise in the east? (4 min)
- Lesson 156: Why is the night sky dark? (4 min)
- Lesson 157: Are the best telescopes all in space? (4 min)
- Lesson 158: Are planets rare in our galaxy? (4 min)
- Lesson 159: Are sunspots cold? (4 min)
- Lesson 160: Does it rain diamonds inside Neptune? (4 min)
- Lesson 161: Does Mars have earthquakes? (4 min)
- Lesson 162: Did comets bring Earth's water? (4 min)
- Lesson 163: Why crash a spacecraft on purpose? (4 min)
- Lesson 164: Can an asteroid hit the Moon? (4 min)
- Lesson 165: Can you see an eclipse from the Moon? (4 min)
- Lesson 166: Can solar panels work at Jupiter? (4 min)
- Lesson 167: Have only a few people visited the space station? (4 min)
- Lesson 168: Is rocket fuel hot? (4 min)
- Lesson 169: Do only earthquakes make tsunamis? (4 min)
- Lesson 170: Is a stronger hurricane always a bigger one? (4 min)
- Lesson 171: Do volcanoes give off more carbon dioxide than people? (4 min)
- Lesson 172: Does Britain have earthquakes? (4 min)
- Lesson 173: Did NASA spend millions on a space pen? (4 min)
- Lesson 174: Did NASA invent Velcro? (4 min)
- Lesson 175: Is your star sign where the Sun really was? (4 min)
- Lesson 176: Do people in the north and south see the same stars? (4 min)
- Lesson 177: Do all planets circle a star? (4 min)
- Lesson 178: Do you still see the Sun after it has set? (4 min)
- Lesson 179: Do comets crash into the Sun? (4 min)
- Lesson 180: Could a Mars dust storm knock over an astronaut? (4 min)
- Lesson 181: Are auroras only on Earth? (4 min)
- Lesson 182: Is the Sun a perfect ball? (4 min)
- Lesson 183: Has anything landed on Venus? (4 min)
- Lesson 184: What does the Moon smell like? (4 min)
- Lesson 185: Did astronauts drive a car on the Moon? (4 min)
- Lesson 186: Can a rocket trigger lightning? (4 min)
- Lesson 187: Has a rocket reached orbit from continental Europe? (4 min)
- Lesson 188: How big was the first satellite? (4 min)
- Lesson 189: Can you grow food in space? (4 min)
- Lesson 190: Can satellites see through clouds? (4 min)
- Lesson 191: Is Antarctica a desert? (4 min)
- Lesson 192: How heavy is a cloud? (4 min)
- Lesson 193: Does Sahara dust feed the Amazon? (4 min)
- Lesson 194: Why do stars in Webb pictures have spikes? (4 min)
- Lesson 195: Do the stars vanish in daytime? (4 min)
- Lesson 196: Was the Big Bang an explosion? (4 min)
- Lesson 197: Are volcanoes erupting on Venus today? (4 min)
- Lesson 198: Has a spacecraft landed on a comet? (4 min)
- Lesson 199: Are there caves on the Moon? (4 min)
- Lesson 200: Why are there no stars in Moon landing photos? (4 min)
- Lesson 201: Is a solar eclipse rare? (4 min)
- Lesson 202: Can plants grow in Moon soil? (4 min)
- Lesson 203: Where did the Moon come from? (4 min)
- Lesson 204: Is Saturn V still the most powerful rocket? (4 min)
- Lesson 205: Are astronauts crushed at launch? (4 min)
- Lesson 206: How did the first person in orbit land? (4 min)
- Lesson 207: Why are spacecraft wrapped in gold foil? (4 min)
- Lesson 208: How do we talk to faraway spacecraft? (4 min)
- Lesson 209: Do all space capsules land in the sea? (4 min)
- Lesson 210: Do only space agencies send crews to the space station? (4 min)
- Lesson 211: Is landing on the Moon easy now? (4 min)
- Lesson 212: Is a full Moon twice as bright as a half Moon? (4 min)
- Lesson 213: Is the space station quiet? (4 min)
- Lesson 214: Are plane trails just smoke? (4 min)
- Lesson 215: What powers the space station? (4 min)
- Lesson 216: Can a meteor shower turn into a storm? (4 min)
- Lesson 217: Can you see Uranus without a telescope? (4 min)
- Lesson 218: Do most stars live alone like the Sun? (4 min)
- Lesson 219: Does it snow on Mars? (4 min)
- Lesson 220: Have we watched a comet hit a planet? (4 min)
- Lesson 221: Is there a phone network on the Moon? (4 min)
- Lesson 222: Who was the first woman in space? (4 min)
- Lesson 223: Has anything landed on another planet's moon? (4 min)
- Lesson 224: Was the Sahara once green? (4 min)
- Lesson 225: Are meteors best after midnight? (4 min)
- Lesson 226: Do you need a telescope for a meteor shower? (4 min)
- Lesson 227: Is the earliest sunset on the shortest day? (4 min)
- Lesson 228: Can you see a planet cross the Sun? (4 min)
- Lesson 229: What does Earth look like from Mars? (4 min)
- Lesson 230: Does the full Moon make people act strangely? (4 min)
- Lesson 231: How high did the first liquid-fuel rocket fly? (4 min)
- Lesson 232: Does a countdown always run straight from ten? (4 min)
- Lesson 233: Who took the first photo of the whole Earth? (4 min)
- Lesson 234: Does food taste different in space? (4 min)
- Lesson 235: How does a toilet work in space? (4 min)
- Lesson 236: Are there clouds that glow at night? (4 min)
- Lesson 237: Is the shortest day the coldest? (4 min)
- Lesson 238: Can you see Jupiter's moons with binoculars? (4 min)
- Lesson 239: Is the biggest body in the asteroid belt a planet? (4 min)
- Lesson 240: Can the Moon trigger earthquakes? (4 min)
- Lesson 241: Can satellites be launched from the space station? (4 min)
- Lesson 242: Can a plane fly to space? (4 min)
- Lesson 243: What is inside the nose of a rocket? (4 min)
- Lesson 244: Is most of an iceberg under water? (4 min)
- Lesson 245: Has falling space junk ever hit anyone? (4 min)
- Lesson 246: How long can a person stay in space? (4 min)
- Lesson 247: Is there a south pole star? (4 min)
- Lesson 248: Are the dark patches in the Milky Way empty? (4 min)
- Lesson 249: Is there a planet where it rains glass? (4 min)
- Lesson 250: Did an asteroid wipe out the dinosaurs? (4 min)
- Lesson 251: Are there mountains on the Moon? (4 min)
- Lesson 252: Can a launch tower catch a rocket? (4 min)
- Lesson 253: Have we heard sounds from Mars? (4 min)
- Lesson 254: Can satellites see autumn leaves change colour? (4 min)
- Lesson 255: Can astronauts walk right after landing? (4 min)
- Lesson 256: Can astronauts vote from space? (4 min)
- Lesson 257: Can you see the Big Dipper all year? (4 min)
- Lesson 258: Is Mars dust harmful to astronauts? (4 min)
- Lesson 259: Are the planets as close together as in pictures? (4 min)
- Lesson 260: What did astronauts leave on the Moon? (4 min)
- Lesson 261: Can we see light from the Big Bang? (4 min)
- Lesson 262: How many countries can launch people into space? (4 min)
- Lesson 263: Can a rocket be 3D printed? (4 min)
- Lesson 264: What is a bomb cyclone? (4 min)
- Lesson 265: Can animals sense an earthquake coming? (4 min)
- Lesson 266: Can people live a year in a pretend Mars base? (4 min)
- Lesson 267: Is the North Star part of the Big Dipper? (4 min)
- Lesson 268: Have pieces of Mars landed on Earth? (4 min)
- Lesson 269: Does the Moon have a tail? (4 min)
- Lesson 270: Can moonlight make a rainbow? (4 min)
- Lesson 271: Does the Sun have holes? (4 min)
- Lesson 272: Does Europe have its own crew spacecraft? (4 min)
- Lesson 273: How did Webb fit inside a rocket? (4 min)
- Lesson 274: Does a quiet hurricane season mean no danger? (4 min)
- Lesson 275: Do scientists still use the Richter scale? (4 min)
- Lesson 276: Why do astronauts avoid bread? (4 min)
- Lesson 277: Did Galileo invent the telescope? (4 min)
- Lesson 278: Can we photograph planets around other stars? (4 min)
- Lesson 279: What is the heart on Pluto? (4 min)
- Lesson 280: Where is the biggest canyon in the Solar System? (4 min)
- Lesson 281: Did Moon dust give astronauts hay fever? (4 min)
- Lesson 282: How many rovers have driven on Mars? (4 min)
- Lesson 283: Can your name fly to space? (4 min)
- Lesson 284: Can volcanoes make lightning? (4 min)
- Lesson 285: Is Earth's inner core spinning backwards? (4 min)
- Lesson 286: Is the eye of a hurricane calm? (4 min)
- Lesson 287: Are there planets with two suns? (4 min)
- Lesson 288: Can a gamma-ray burst harm Earth? (4 min)
- Lesson 289: Is the Sun yellow? (4 min)
- Lesson 290: Which planet has the shortest day? (4 min)
- Lesson 291: Is radiation dangerous on the Moon? (4 min)
- Lesson 292: Do Mars rover wheels wear out? (4 min)
- Lesson 293: Do satellites have to dodge space junk? (4 min)
- Lesson 294: Can a volcano erupt under ice? (4 min)
- Lesson 295: Does the ozone hole cause global warming? (4 min)
- Lesson 296: Can you see country borders from space? (4 min)
- Lesson 297: What makes a ring around the Moon? (4 min)
- Lesson 298: Are new stars still being born? (4 min)
- Lesson 299: Did Earth once have a ring? (4 min)
- Lesson 300: Are Venus's clouds made of water? (4 min)
- Lesson 301: Did only Apollo bring Moon rocks home? (4 min)
- Lesson 302: Can a crew survive a rocket failure? (4 min)
- Lesson 303: Can a spacecraft land on a runway? (4 min)
- Lesson 304: What does lightning look like from space? (4 min)
- Lesson 305: Is GPS the only satellite navigation? (4 min)
- Lesson 306: Is a planetary nebula made of planets? (4 min)
- Lesson 307: Are there more stars than grains of sand? (4 min)
- Lesson 308: Could you breathe on Mars? (4 min)
- Lesson 309: Is a hidden planet Nibiru heading for Earth? (4 min)
- Lesson 310: Is the Moon full of valuable helium? (4 min)
- Lesson 311: Can a rocket launch from a plane? (4 min)
- Lesson 312: Do space probes take colour photos like phones? (4 min)
- Lesson 313: Can you fly to space for just a few minutes? (4 min)
- Lesson 314: Is a supernova just a bigger nova? (4 min)
- Lesson 315: Is there a black hole in almost every galaxy? (4 min)
- Lesson 316: What would happen if you fell into a black hole? (4 min)
- Lesson 317: Are gravitational waves passing through you right now? (4 min)
- Lesson 318: Could you fly through a nebula? (4 min)
- Lesson 319: Do newborn stars blow away their nursery? (4 min)
- Lesson 320: Why is a star cluster like a class photo? (4 min)
- Lesson 321: Can you really see seven Pleiades? (4 min)
- Lesson 322: Is a galaxy just a giant star cluster? (4 min)
- Lesson 323: How many galaxies can a telescope find in a week? (4 min)
- Lesson 324: Does time slow down near a black hole? (4 min)
- Lesson 325: What is a black hole star? (4 min)
- Lesson 326: Were pulsars first thought to be aliens? (4 min)
- Lesson 327: Did Einstein think we would ever detect gravitational waves? (4 min)
- Lesson 328: Is there a giant eye in space? (4 min)
- Lesson 329: Is there a nebula that looks like a brain? (4 min)
- Lesson 330: Are all star clusters the same kind? (4 min)
- Lesson 331: Does the bright star of Taurus belong to its cluster? (4 min)
- Lesson 332: Did Magellan discover the Magellanic Clouds? (4 min)
- Lesson 333: Can a galaxy die? (4 min)
- Lesson 334: Can a black hole die? (4 min)
- Lesson 335: Does our galaxy's black hole flicker? (4 min)
- Lesson 336: Can pulsars guide a spacecraft like GPS? (4 min)
- Lesson 337: Does a black hole crash make mass vanish? (4 min)
- Lesson 338: Why are so many nebulae red? (4 min)
- Lesson 339: Why does the Horsehead Nebula look dark? (4 min)
- Lesson 340: Why do nebulae have animal names? (4 min)
- Lesson 341: Is there a beehive in the sky? (4 min)
- Lesson 342: Was the Milky Way once thought to be the whole universe? (4 min)
- Lesson 343: Can a galaxy act like a magnifying glass? (4 min)
- Lesson 344: Do black holes spin? (4 min)
- Lesson 345: Has the first photographed black hole changed? (4 min)
- Lesson 346: Is there a pulsar map on the Voyager record? (4 min)
- Lesson 347: How many cosmic crashes have we detected? (4 min)
- Lesson 348: Were the Pillars of Creation destroyed? (4 min)
- Lesson 349: Is an exploded star still expanding? (4 min)
- Lesson 350: Are the stars of the Big Dipper a family? (4 min)
- Lesson 351: Are some star clusters almost as old as the universe? (4 min)
- Lesson 352: How can we know our galaxy's shape from inside it? (4 min)
- Lesson 353: Are all galaxies spirals? (4 min)
- Lesson 354: Can a black hole be the brightest thing in the universe? (4 min)
- Lesson 355: Do black holes shoot jets? (4 min)
- Lesson 356: Did black holes come before galaxies? (4 min)
- Lesson 357: Can a black hole be asleep? (4 min)
- Lesson 358: Do stars circle the black hole at the centre of our galaxy? (4 min)
- Lesson 359: Can a black hole tear a star apart? (4 min)
- Lesson 360: Could a particle collider make a dangerous black hole? (4 min)
- Lesson 361: Could Earth be squeezed into a black hole? (4 min)
- Lesson 362: Were the first exoplanets found around a dead star? (4 min)
- Lesson 363: Is a neutron star made of the strongest stuff in the universe? (4 min)
- Lesson 364: Can a neutron star have mountains? (4 min)
- Lesson 365: Where does the gold in your ring come from? (4 min)
- Lesson 366: What was the heaviest black hole crash ever detected? (4 min)
- Lesson 367: Does the universe have a gravitational hum? (4 min)
- Lesson 368: Can we catch gravitational waves from space? (4 min)
- Lesson 369: Did we see gravitational waves from the Big Bang? (4 min)
- Lesson 370: Can a star look younger by stealing from a neighbour? (4 min)
- Lesson 371: Did we send a message to a star cluster? (4 min)
- Lesson 372: Can we see planets being born? (4 min)
- Lesson 373: Do baby stars shoot jets? (4 min)
- Lesson 374: Can a nebula be colder than empty space? (4 min)
- Lesson 375: Is there alcohol floating in space? (4 min)
- Lesson 376: Are there footballs made of carbon in space? (4 min)
- Lesson 377: Can light echo like sound? (4 min)
- Lesson 378: Can a star explode bright enough to see in daytime? (4 min)
- Lesson 379: When did we last see a star explode in our galaxy? (4 min)
- Lesson 380: Did anyone see a supernova with their own eyes in modern times? (4 min)
- Lesson 381: Does the Sun have lost brothers and sisters? (4 min)
- Lesson 382: Do star clusters leave tails behind them? (4 min)
- Lesson 383: How many globular clusters circle our galaxy? (4 min)
- Lesson 384: What would the night sky look like inside a star cluster? (4 min)
- Lesson 385: Do stars in a crowded cluster crash into each other? (4 min)
- Lesson 386: Do the spiral arms of a galaxy spin like a wheel? (4 min)
- Lesson 387: Does the Milky Way have moons? (4 min)
- Lesson 388: Has the Milky Way swallowed other galaxies? (4 min)
- Lesson 389: When galaxies collide, do the stars crash? (4 min)
- Lesson 390: Do galaxies live in groups? (4 min)
- Lesson 391: Can a galaxy lose its gas like a jellyfish? (4 min)
- Lesson 392: Are there giant bubbles above our galaxy? (4 min)
- Lesson 393: Is there a galaxy shaped like a hat? (4 min)
- Lesson 394: What was the first black hole ever found? (4 min)
- Lesson 395: Do black holes burp? (4 min)
- Lesson 396: Are there medium-sized black holes? (4 min)
- Lesson 397: Can a pulsar eat its partner star? (4 min)
- Lesson 398: What is the clearest gravitational wave caught so far? (4 min)
- Lesson 399: How many black holes are in the Milky Way? (4 min)
- Lesson 400: What is the biggest star nursery near us? (4 min)
- Lesson 401: Did an exploded star help make our Solar System? (4 min)
- Lesson 402: Where are a star cluster's missing black holes? (4 min)
- Lesson 403: Why are crowded star clusters full of fast pulsars? (4 min)
- Lesson 404: Can one star cluster hold four generations of stars? (4 min)
- Lesson 405: Which heavy star cluster in our galaxy is still very young? (4 min)
- Lesson 406: Is every galaxy flying away from us? (4 min)
- Lesson 407: Do small galaxies have giant black holes too? (4 min)
- Lesson 408: What did the Milky Way look like as a baby? (4 min)
- Lesson 409: Could a balloon float up into space? (4 min)
- Lesson 410: Why does the space station's path look like a wave on a map? (4 min)
- Lesson 411: How low can a satellite fly? (4 min)
- Lesson 412: Why is the space station's orbit tilted? (4 min)
- Lesson 413: What happens to water poured out into space? (4 min)
- Lesson 414: Do satellites ever crash into each other? (4 min)
- Lesson 415: Can astronauts lose things in space? (4 min)
- Lesson 416: Why do we have time zones? (4 min)
- Lesson 417: Why doesn't our air drift off into space? (4 min)
- Lesson 418: How thin is the ozone layer? (4 min)
- Lesson 419: What is the greenhouse effect? (4 min)
- Lesson 420: When does summer really start? (4 min)
- Lesson 421: Can you see another galaxy with your own eyes? (4 min)
- Lesson 422: Can a meteor make a boom you can hear? (4 min)
- Lesson 423: Is there a centre of the universe? (4 min)
- Lesson 424: Why are there no green stars? (4 min)
- Lesson 425: What is SETI listening for? (4 min)
- Lesson 426: Is space cold? (4 min)
- Lesson 427: Can you see a single star in another galaxy? (4 min)
- Lesson 428: Where exactly is Earth in the Milky Way? (4 min)
- Lesson 429: Why doesn't the Sun explode? (4 min)
- Lesson 430: Could you feel the solar wind? (4 min)
- Lesson 431: Will the Sun swallow the Earth? (4 min)
- Lesson 432: Why are so many meteorites found in Antarctica? (4 min)
- Lesson 433: Can an asteroid have its own moon? (4 min)
- Lesson 434: Could you land on Jupiter? (4 min)
- Lesson 435: What are Jupiter's stripes? (4 min)
- Lesson 436: Is Pluto sometimes closer to the Sun than Neptune? (4 min)
- Lesson 437: Why is Mercury covered in craters? (4 min)
- Lesson 438: How long is a year on Neptune? (4 min)
- Lesson 439: How did the planets get their names? (4 min)
- Lesson 440: Why does every full moon have a name? (4 min)
- Lesson 441: Why does the Moon follow you when you drive? (4 min)
- Lesson 442: Why does the Moon rise later every day? (4 min)
- Lesson 443: What was the first rocket to reach space? (4 min)
- Lesson 444: How long did it take to reach Pluto? (4 min)
- Lesson 445: What is a rideshare launch? (4 min)
- Lesson 446: Why can a rocket's plume glow in a dark sky? (4 min)
- Lesson 447: Why doesn't the Moon fall down? (4 min)
- Lesson 448: How do the planets stay in orbit around the Sun? (4 min)
- Lesson 449: Can two satellites share the same orbit? (4 min)
- Lesson 450: Why do some satellites suddenly flash like a star? (4 min)
- Lesson 451: What is the most people ever aboard the space station at once? (4 min)
- Lesson 452: Where is the best view of Earth on the space station? (4 min)
- Lesson 453: How do astronauts sleep in space? (4 min)
- Lesson 454: Who runs the space station? (4 min)
- Lesson 455: What time is it on the space station? (4 min)
- Lesson 456: Why do astronauts exercise every day? (4 min)
- Lesson 457: Does space junk stay up there forever? (4 min)
- Lesson 458: What made the most space junk ever? (4 min)
- Lesson 459: Is there a law against leaving junk in space? (4 min)
- Lesson 460: Can a fleck of paint damage a spacecraft? (4 min)
- Lesson 461: How much water does Earth have? (4 min)
- Lesson 462: Where are the hottest and coldest places on Earth? (4 min)
- Lesson 463: Why does Earth spin? (4 min)
- Lesson 464: How deep is the ocean? (4 min)
- Lesson 465: Why is the ocean salty? (4 min)
- Lesson 466: What is a red giant? (4 min)
- Lesson 467: What is dark matter? (4 min)
- Lesson 468: Are day and night really equal at the equinox? (4 min)
- Lesson 469: Why was the Spitzer telescope painted black? (4 min)
- Lesson 470: How far can the Hubble telescope see? (4 min)
- Lesson 471: What will be the biggest telescope on Earth? (4 min)
- Lesson 472: When was the first radio telescope built? (4 min)
- Lesson 473: What is the Cat's Head Nebula? (4 min)
- Lesson 474: How old is the Sun? (4 min)
- Lesson 475: How big is a sunspot? (4 min)
- Lesson 476: How did Saturn get its rings? (4 min)
- Lesson 477: What was Neptune's Great Dark Spot? (4 min)
- Lesson 478: Has a spacecraft ever landed on an asteroid? (4 min)
- Lesson 479: Why is Venus called Earth's twin? (4 min)
- Lesson 480: What does the Sun look like from Mercury? (4 min)
- Lesson 481: What is the Oort Cloud? (4 min)
- Lesson 482: How long is a day on the Moon? (4 min)
- Lesson 483: What is a king tide? (4 min)
- Lesson 484: Is the Moon drifting away from Earth? (4 min)
- Lesson 485: What does NASA stand for, and when did it start? (4 min)
- Lesson 486: How heavy was the Space Shuttle? (4 min)
- Lesson 487: Has the space station ever had a leak? (4 min)
- Lesson 488: What is a CubeSat? (4 min)
- Lesson 489: How long does a satellite last? (4 min)
- Lesson 490: What is a spacewalk? (4 min)
- Lesson 491: How do you become an astronaut? (4 min)
- Lesson 492: What is Starlink? (4 min)
- Lesson 493: Can a spy satellite read a newspaper? (4 min)
- Lesson 494: Do astronauts see auroras from the space station? (4 min)
- Lesson 495: How do astronauts call home? (4 min)
- Lesson 496: How do astronauts wash their hair? (4 min)
- Lesson 497: Do astronauts get sick in space? (4 min)
- Lesson 498: Why do astronauts wear orange suits for launch? (4 min)
- Lesson 499: How do astronauts do their laundry? (4 min)
- Lesson 500: Can we clean up space junk? (4 min)
- Lesson 501: What is Earth's air made of? (4 min)
- Lesson 502: Why is Earth called the blue planet? (4 min)
- Lesson 503: How do satellites measure rain? (4 min)
- Lesson 504: Which star is closest to us? (4 min)
- Lesson 505: What is the biggest star we know? (4 min)
- Lesson 506: What is a black dwarf? (4 min)
- Lesson 507: What is the closest planet outside the Solar System? (4 min)
- Lesson 508: If light has no mass, how can a black hole trap it? (4 min)
- Lesson 509: What is the Carina Nebula? (4 min)
- Lesson 510: Can you see a nebula with binoculars? (4 min)
- Lesson 511: What is the Triangulum Galaxy? (4 min)
- Lesson 512: What is a starburst galaxy? (4 min)
- Lesson 513: What was the Hubble Deep Field? (4 min)
- Lesson 514: Does the Sun make a sound? (4 min)
- Lesson 515: Does Mercury have air? (4 min)
- Lesson 516: Which planet has the most moons? (4 min)
- Lesson 517: Can you see Saturn's rings through a small telescope? (4 min)
- Lesson 518: What are meteorites made of? (4 min)
- Lesson 519: Is Pluto bigger than the Moon? (4 min)
- Lesson 520: How do Mars rovers get their power? (4 min)
- Lesson 521: Why is Jupiter so big? (4 min)
- Lesson 522: Could you walk on an asteroid like in the movies? (4 min)
- Lesson 523: Do other planets have seasons? (4 min)
- Lesson 524: Why did nobody go back to the Moon after Apollo? (4 min)
- Lesson 525: Why does the Moon sometimes look orange? (4 min)
- Lesson 526: Is there water on the Moon? (4 min)
- Lesson 527: How long does it take to get to the Moon? (4 min)
- Lesson 528: How much does a rocket launch cost? (4 min)
- Lesson 529: Why are rockets so tall? (4 min)
- Lesson 530: Will people ever travel to the stars? (4 min)
- Lesson 531: What is a Lagrange point? (4 min)
- Lesson 532: Can you see a satellite with your own eyes? (4 min)
- Lesson 533: How do satellites talk to each other with lasers? (4 min)
- Lesson 534: Where do old spacecraft go to crash? (4 min)
- Lesson 535: Can people on a plane watch a satellite burn up? (4 min)
- Lesson 536: Who keeps count of space junk? (4 min)
- Lesson 537: Can a satellite see how far the ground moved in an earthquake? (4 min)
- Lesson 538: How do scientists watch volcanoes from space? (4 min)
- Lesson 539: Did Arctic sea ice tie its lowest winter peak? (4 min)
- Lesson 540: Can satellites see wildfire smoke from space? (4 min)
- Lesson 541: When was a record short day measured? (4 min)
- Lesson 542: Do satellites spoil telescope pictures? (4 min)
- Lesson 543: Why do satellites bother radio telescopes? (4 min)
- Lesson 544: What is NASA's SPHEREx telescope mapping? (4 min)
- Lesson 545: What is the Rubin Observatory looking for? (4 min)
- Lesson 546: Why are phones and Wi-Fi limited near some radio telescopes? (4 min)
- Lesson 547: How light can a black hole be? (4 min)
- Lesson 548: Is a new gravitational wave detector being built in India? (4 min)
- Lesson 549: Could the Sun become a black hole? (4 min)
- Lesson 550: Is the jet from black hole M87 faster than light? (4 min)
- Lesson 551: Is there a nebula shaped like a butterfly? (4 min)
- Lesson 552: What is the Cat's Paw Nebula? (4 min)
- Lesson 553: What is the farthest galaxy we have seen? (4 min)
- Lesson 554: Why is the Cigar Galaxy so bright? (4 min)
- Lesson 555: Can a galaxy have almost no stars? (4 min)
- Lesson 556: What is solar maximum? (4 min)
- Lesson 557: What does an X-class solar flare mean? (4 min)
- Lesson 558: What has Parker Solar Probe found near the Sun? (4 min)
- Lesson 559: What is the interstellar comet 3I/ATLAS? (4 min)
- Lesson 560: How many visitors from other stars have we found? (4 min)
- Lesson 561: What is the Hera spacecraft looking at? (4 min)
- Lesson 562: Why will Europa Clipper orbit Jupiter, not Europa? (4 min)
- Lesson 563: What will BepiColombo do at Mercury? (4 min)
- Lesson 564: Did Webb find a new moon of Uranus? (4 min)
- Lesson 565: Is a hidden Planet Nine out there? (4 min)
- Lesson 566: What did the Artemis II astronauts eat? (4 min)
- Lesson 567: How did the Artemis II crew exercise on the way to the Moon? (4 min)
- Lesson 568: Why did the Artemis II crew carry a plush toy? (4 min)
- Lesson 569: What is the New Glenn rocket? (4 min)
- Lesson 570: How many rockets launch each year? (4 min)
- Lesson 571: Can a satellite be refuelled in orbit? (4 min)
- Lesson 572: Could data centres work in space? (4 min)
- Lesson 573: Can a dead satellite send a strange radio flash? (4 min)
- Lesson 574: How many old satellites fall back to Earth each day? (4 min)
- Lesson 575: Can satellites follow a giant iceberg? (4 min)
- Lesson 576: What is an atmospheric river? (4 min)
- Lesson 577: What is the jet stream? (4 min)
- Lesson 578: What is a dark sky park? (4 min)
- Lesson 579: Can a planet survive when its star dies? (4 min)
- Lesson 580: Can we find the star that exploded? (4 min)
- Lesson 581: Can water survive near the Milky Way's central black hole? (4 min)
- Lesson 582: What is a reflection nebula? (4 min)
- Lesson 583: What is the oldest quasar we know? (4 min)
- Lesson 584: Can anyone help spot galaxies that bend light? (4 min)
- Lesson 585: Can a galaxy carry scars of a past collision? (4 min)
- Lesson 586: What is NASA's PUNCH mission watching? (4 min)
- Lesson 587: Can a space telescope find a new comet by accident? (4 min)
- Lesson 588: Is NASA building a base on the Moon? (4 min)
- Lesson 589: Can you watch a solar eclipse from a plane? (4 min)
- Lesson 590: Can Starship carry people to the Moon? (4 min)
- Lesson 591: Why does a dead satellite tumble? (4 min)
- Lesson 592: What is airglow? (4 min)
- Lesson 593: What are cosmic rays? (4 min)
- Lesson 594: Is there a planet made of diamond? (4 min)
- Lesson 595: What is a zombie star? (4 min)
- Lesson 596: What is the Great Attractor? (4 min)
- Lesson 597: What is a sunquake? (4 min)
- Lesson 598: Does Uranus smell like rotten eggs? (4 min)
- Lesson 599: What are the strange swirls on the Moon? (4 min)
- Lesson 600: What is a sounding rocket? (4 min)

## Intermediate (300 lessons)

- Lesson 1: Orbital speed: lower means faster (5 min)
- Lesson 2: The wobbling sky: precession (5 min)
- Lesson 3: Escape velocity: leaving for good (5 min)
- Lesson 4: Kessler syndrome: when debris breeds debris (5 min)
- Lesson 5: Reading a seismogram (5 min)
- Lesson 6: Tides: the Moon pulls unevenly (5 min)
- Lesson 7: Reading the space weather forecast (5 min)
- Lesson 8: Why do rockets throw parts of themselves away? (5 min)
- Lesson 9: Why are satellites easiest to see just after dusk? (5 min)
- Lesson 10: Why are the rocky planets close to the Sun and the giants far away? (5 min)
- Lesson 11: Why does the Moon turn exactly once on each trip around Earth? (5 min)
- Lesson 12: Why are tides stronger at full moon and new moon? (5 min)
- Lesson 13: Why is the Webb telescope parked 1.5 million kilometres from Earth? (5 min)
- Lesson 14: A spacecraft fires its engine to catch up: does it gain or fall behind? (5 min)
- Lesson 15: Why is there not a solar eclipse every month? (5 min)
- Lesson 16: Why do you see different constellations in winter and in summer? (5 min)
- Lesson 17: Why does Mars sometimes go backwards in the sky? (5 min)
- Lesson 18: Why does a tsunami grow only near the shore? (5 min)
- Lesson 19: Why can you only fly to Mars every couple of years? (5 min)
- Lesson 20: What do sunspots tell us about the next few years? (5 min)
- Lesson 21: Why does Venus have phases like the Moon? (5 min)
- Lesson 22: Why does a day on Mercury last two of its years? (5 min)
- Lesson 23: Why does the Sun not set in the Arctic in June? (5 min)
- Lesson 24: Why do Saturn's rings seem to vanish? (5 min)
- Lesson 25: Where did the air of Mars go? (5 min)
- Lesson 26: How do we know a comet came from another star? (5 min)
- Lesson 27: Does Earth rise and set in the Moon's sky? (5 min)
- Lesson 28: Why are some earthquakes felt much farther away? (5 min)
- Lesson 29: What does Webb see inside a cloud of dust? (5 min)
- Lesson 30: Why do the meteors of a shower seem to come from one point? (5 min)
- Lesson 31: Why does the space station fire its engines? (5 min)
- Lesson 32: How does GPS know where you are? (5 min)
- Lesson 33: How does Earth's magnetic field protect you? (5 min)
- Lesson 34: Why do we need leap years? (5 min)
- Lesson 35: Why is Uranus tipped on its side? (5 min)
- Lesson 36: Is there an ocean under Europa's ice? (5 min)
- Lesson 37: Is Jupiter's Great Red Spot shrinking? (5 min)
- Lesson 38: Why does the Moon turn red in a lunar eclipse? (5 min)
- Lesson 39: How can a rocket push in empty space? (5 min)
- Lesson 40: Why is the Sun's corona hotter than its surface? (5 min)
- Lesson 41: How did Artemis II turn around at the Moon? (5 min)
- Lesson 42: Why go to the Moon's south pole? (5 min)
- Lesson 43: How do we find planets around other stars? (5 min)
- Lesson 44: How do you photograph a black hole? (5 min)
- Lesson 45: What are gravitational waves? (5 min)
- Lesson 46: Can we push an asteroid off course? (5 min)
- Lesson 47: Apophis will pass closer than some satellites (5 min)
- Lesson 48: How far is one light-day from Earth? (5 min)
- Lesson 49: Can sunlight push a spacecraft? (5 min)
- Lesson 50: What holds galaxies together? (5 min)
- Lesson 51: Why must a Moon lander refuel in orbit? (5 min)
- Lesson 52: How did a piece of asteroid Bennu reach Earth? (5 min)
- Lesson 53: Does Enceladus spray its ocean into space? (5 min)
- Lesson 54: How does a flyby speed up a spacecraft? (5 min)
- Lesson 55: Why is Io the most volcanic world? (5 min)
- Lesson 56: What is a magnetar? (5 min)
- Lesson 57: Why is Lucy visiting Jupiter's Trojans? (5 min)
- Lesson 58: What came back from the Moon's far side? (5 min)
- Lesson 59: What are the bright spots on Ceres? (5 min)
- Lesson 60: What are the Van Allen belts? (5 min)
- Lesson 61: How does Hubble turn without engines? (5 min)
- Lesson 62: Why can a solar storm pull satellites down? (5 min)
- Lesson 63: How did a satellite see a tsunami at sea? (5 min)
- Lesson 64: Can a volcano cool the whole planet? (5 min)
- Lesson 65: Why does the length of Earth's day change? (5 min)
- Lesson 66: Will the Milky Way crash into Andromeda? (5 min)
- Lesson 67: Why are we losing the stars? (5 min)
- Lesson 68: What is the faint cone of light after dusk? (5 min)
- Lesson 69: Why are some auroras red and others green? (5 min)
- Lesson 70: Why is it so hard to fly to the Sun? (5 min)
- Lesson 71: Why are sunsets blue on Mars? (5 min)
- Lesson 72: Can the solar wind make water on the Moon? (5 min)
- Lesson 73: Why is Moon dust such a problem? (5 min)
- Lesson 74: Why are some Moon rocks magnetic? (5 min)
- Lesson 75: Why does the dark part of a crescent Moon glow? (5 min)
- Lesson 76: Why can we see more than half of the Moon? (5 min)
- Lesson 77: Why do rockets ease off soon after liftoff? (5 min)
- Lesson 78: How does a rocket booster land itself? (5 min)
- Lesson 79: Why is water poured under a rocket at launch? (5 min)
- Lesson 80: How does a rover land on Mars? (5 min)
- Lesson 81: Why does a hurricane weaken over land? (5 min)
- Lesson 82: Why do the biggest earthquakes strike where plates dive? (5 min)
- Lesson 83: How does a satellite measure the height of the sea? (5 min)
- Lesson 84: Why does the Geminid shower come from an asteroid? (5 min)
- Lesson 85: Why does the Orion Nebula glow? (5 min)
- Lesson 86: Why do pulsars flash like lighthouses? (5 min)
- Lesson 87: Why does Saturn have so many tiny moons? (5 min)
- Lesson 88: What colour are Uranus and Neptune really? (5 min)
- Lesson 89: How can craters tell the age of a surface? (5 min)
- Lesson 90: How does a big rocket steer? (5 min)
- Lesson 91: Why do some satellites fly long, tilted orbits? (5 min)
- Lesson 92: Where do dead geostationary satellites go? (5 min)
- Lesson 93: How do satellites spot wildfires? (5 min)
- Lesson 94: How can a blinking star measure the universe? (5 min)
- Lesson 95: Why are the Pleiades blue, and will they stay together? (5 min)
- Lesson 96: Why does the Sun's surface look like boiling rice? (5 min)
- Lesson 97: Why does Jupiter have the brightest auroras? (5 min)
- Lesson 98: Why are there gaps in the asteroid belt? (5 min)
- Lesson 99: Why are the Moon's dark seas almost all on the near side? (5 min)
- Lesson 100: Why is a hydrogen rocket's flame almost invisible? (5 min)
- Lesson 101: Why doesn't Europa's ocean freeze? (5 min)
- Lesson 102: How does it rain on Titan? (5 min)
- Lesson 103: Phobos, Triton and Charon: moons that break the rules (5 min)
- Lesson 104: What is it like inside a giant planet? (5 min)
- Lesson 105: How does stretched light show the universe is expanding? (5 min)
- Lesson 106: What do the tiny spots in the Big Bang's afterglow tell us? (5 min)
- Lesson 107: Where did the first atoms come from? (5 min)
- Lesson 108: What is dark energy? (5 min)
- Lesson 109: How does a smash of galaxy clusters reveal dark matter? (5 min)
- Lesson 110: When did the first stars switch on? (5 min)
- Lesson 111: What is the cosmic web? (5 min)
- Lesson 112: What was cosmic inflation? (5 min)
- Lesson 113: Why does a star's mass decide how long it lives? (5 min)
- Lesson 114: What happens when a star runs out of hydrogen? (5 min)
- Lesson 115: What is a white dwarf, and how heavy can it get? (5 min)
- Lesson 116: What is a brown dwarf? (5 min)
- Lesson 117: What does ultraviolet light show that visible light hides? (5 min)
- Lesson 118: How does a massive star build an iron core and explode? (5 min)
- Lesson 119: Why do red dwarf stars flare so violently? (5 min)
- Lesson 120: What is a Wolf-Rayet star? (5 min)
- Lesson 121: How can we tell a rocky planet from a gas planet? (5 min)
- Lesson 122: How does Webb read the air of a faraway planet? (5 min)
- Lesson 123: What kinds of planets does our Solar System not have? (5 min)
- Lesson 124: What is a tidally locked planet like? (5 min)
- Lesson 125: How does a star's bent light reveal hidden planets? (5 min)
- Lesson 126: Can a star's tiny sideways wobble reveal a planet? (5 min)
- Lesson 127: Do moons circle planets around other stars? (5 min)
- Lesson 128: What can a star's light spectrum tell us? (5 min)
- Lesson 129: Why do X-ray telescopes need such strange mirrors? (5 min)
- Lesson 130: How can many radio dishes work as one giant telescope? (5 min)
- Lesson 131: How do big telescopes cancel the twinkle? (5 min)
- Lesson 132: How do astronomers name the stars? (5 min)
- Lesson 133: How did black holes get so big so early? (5 min)
- Lesson 134: How does a gas cloud turn into a star? (5 min)
- Lesson 135: What is a T Tauri star? (5 min)
- Lesson 136: What is left after a star explodes? (5 min)
- Lesson 137: What are the small dark blobs inside nebulae? (5 min)
- Lesson 138: Why do planetary nebulae come in so many shapes? (5 min)
- Lesson 139: How do astronomers sort galaxies into types? (5 min)
- Lesson 140: What are the parts of the Milky Way? (5 min)
- Lesson 141: Why is a stream of gas trailing the Magellanic Clouds? (5 min)
- Lesson 142: Why do tiny dwarf galaxies matter? (5 min)
- Lesson 143: What is a galaxy cluster? (5 min)
- Lesson 144: How does Webb find the most distant galaxies? (5 min)
- Lesson 145: How do two spacecraft dock? (5 min)
- Lesson 146: How does Earth's bulge keep an orbit in step with the Sun? (5 min)
- Lesson 147: How can a spacecraft circle an empty point in space? (5 min)
- Lesson 148: How do lasers send data from deep space? (5 min)
- Lesson 149: How does a radar satellite see through clouds and spot ground moving? (5 min)
- Lesson 150: How do twin satellites weigh Earth's water? (5 min)
- Lesson 151: How do we track a small piece of space junk from the ground? (5 min)
- Lesson 152: When does a satellite really have to dodge? (5 min)
- Lesson 153: Why does the ozone hole open over Antarctica each spring? (5 min)
- Lesson 154: How does a satellite measure carbon dioxide from orbit? (5 min)
- Lesson 155: How does El Niño change weather on the other side of the world? (5 min)
- Lesson 156: Why do some volcanoes explode while others ooze? (5 min)
- Lesson 157: Why does a clock near a black hole fall behind? (5 min)
- Lesson 158: Why would a small black hole stretch you more than a giant one? (5 min)
- Lesson 159: How does a black hole launch its jets? (5 min)
- Lesson 160: How do you measure a neutron star the size of a city? (5 min)
- Lesson 161: How do you find a black hole that is not eating? (5 min)
- Lesson 162: How do pulsars listen for gravitational waves? (5 min)
- Lesson 163: How does a black hole tear a star apart? (5 min)
- Lesson 164: How do massive stars blow bubbles in their nebulae? (5 min)
- Lesson 165: Why do galaxies stop making stars? (5 min)
- Lesson 166: How does a galaxy bend light into an Einstein ring? (5 min)
- Lesson 167: How long does sunlight take to get out of the Sun? (5 min)
- Lesson 168: Why does the Sun flip its magnetic poles? (5 min)
- Lesson 169: Where does a solar flare get its energy? (5 min)
- Lesson 170: How do we know how the Moon formed? (5 min)
- Lesson 171: How does the Moon keep Earth's tilt steady? (5 min)
- Lesson 172: Why do upper-stage engines have giant nozzles? (5 min)
- Lesson 173: Solid or liquid boosters: what is the difference? (5 min)
- Lesson 174: How does a spacecraft keep from cooking and freezing? (5 min)
- Lesson 175: Why do astronauts' faces get puffy? (5 min)
- Lesson 176: Why is the space station getting new solar wings? (5 min)
- Lesson 177: How does the space station make its own oxygen? (5 min)
- Lesson 178: Why is magnetic north heading for Siberia? (5 min)
- Lesson 179: How do we know Earth's centre is moving? (5 min)
- Lesson 180: How does a satellite measure how salty the sea is? (5 min)
- Lesson 181: How can a satellite map a sea floor it cannot see? (5 min)
- Lesson 182: Why do the stars rise four minutes earlier each night? (5 min)
- Lesson 183: Why is there more matter than antimatter? (5 min)
- Lesson 184: How does Webb read the dust of planet-shattering crashes? (5 min)
- Lesson 185: Do meteors really just burn up? (5 min)
- Lesson 186: Do black holes of every size work the same way? (5 min)
- Lesson 187: What is a stream of stars? (5 min)
- Lesson 188: What are the Sun's tiny whirlpools? (5 min)
- Lesson 189: How do we know what is inside the Sun? (5 min)
- Lesson 190: Did Venus once have a moon? (5 min)
- Lesson 191: How can a small icy world have rings? (5 min)
- Lesson 192: Is there flowing liquid on Pluto? (5 min)
- Lesson 193: What is hiding deep inside Mars? (5 min)
- Lesson 194: Why are big moons and planets round? (5 min)
- Lesson 195: Why are some tides huge and others tiny? (5 min)
- Lesson 196: How do we spot a brand-new crater on the Moon? (5 min)
- Lesson 197: Could Earth microbes survive on the Moon? (5 min)
- Lesson 198: How does a heat shield survive re-entry? (5 min)
- Lesson 199: How does a spacecraft slow down to leave orbit? (5 min)
- Lesson 200: How does a geostationary satellite keep its slot? (5 min)
- Lesson 201: Why is the Hubble telescope's orbit sinking? (5 min)
- Lesson 202: Why does one anti-satellite test keep threatening satellites for years? (5 min)
- Lesson 203: Why do old rocket stages sometimes explode years later? (5 min)
- Lesson 204: How do shields protect the space station from debris? (5 min)
- Lesson 205: Why is Earth's inside still hot? (5 min)
- Lesson 206: How do we weigh a black hole? (5 min)
- Lesson 207: Why do neutron stars spin so fast? (5 min)
- Lesson 208: Why doesn't a neutron star collapse any further? (5 min)
- Lesson 209: What fills the space between the stars? (5 min)
- Lesson 210: Why do star clusters drift apart? (5 min)
- Lesson 211: Why are globular clusters so old? (5 min)
- Lesson 212: Why are so many stars born in pairs? (5 min)
- Lesson 213: Why do some nebulae glow green? (5 min)
- Lesson 214: Why are some small galaxies missing oxygen? (5 min)
- Lesson 215: Why is the Milky Way's centre hidden from us? (5 min)
- Lesson 216: How do we know the Milky Way is a spiral if we are inside it? (5 min)
- Lesson 217: Why are galaxies different colours? (5 min)
- Lesson 218: Why does the solar wind blow faster from some places? (5 min)
- Lesson 219: Where does the Sun's bubble end? (5 min)
- Lesson 220: What holds Saturn's rings together? (5 min)
- Lesson 221: Why does Venus spin backwards? (5 min)
- Lesson 222: How can crews on Mars be protected from dust? (5 min)
- Lesson 223: Why does an infrared telescope need a sunshade? (5 min)
- Lesson 224: Why are Uranus's and Neptune's magnetic fields so lopsided? (5 min)
- Lesson 225: Why do Saturn's rings have gaps? (5 min)
- Lesson 226: Why does little Mercury have a magnetic field? (5 min)
- Lesson 227: Why are low orbits around the Moon unstable? (5 min)
- Lesson 228: What will Artemis III test before a Moon landing? (5 min)
- Lesson 229: What did Artemis II learn about the Moon? (5 min)
- Lesson 230: How does a transfer orbit carry a spacecraft higher? (5 min)
- Lesson 231: How do two satellites fly in formation? (5 min)
- Lesson 232: Why do satellites glitch over the South Atlantic? (5 min)
- Lesson 233: Why are big satellite constellations a debris risk? (5 min)
- Lesson 234: What survives when a satellite falls, and why design it to burn up? (5 min)
- Lesson 235: Why is debris in geostationary orbit hard to see? (5 min)
- Lesson 236: How can a laser nudge space debris? (5 min)
- Lesson 237: How does a laser map Earth in 3D? (5 min)
- Lesson 238: How is a storm near Iceland different from a hurricane? (5 min)
- Lesson 239: How do astronomers find a star's age? (5 min)
- Lesson 240: Can a star change colour? (5 min)
- Lesson 241: What causes a gamma-ray burst? (5 min)
- Lesson 242: What is an X-ray binary? (5 min)
- Lesson 243: Why do pulsars slow down? (5 min)
- Lesson 244: Why do massive stars form in clusters? (5 min)
- Lesson 245: What are Herbig-Haro objects? (5 min)
- Lesson 246: What is an HII region? (5 min)
- Lesson 247: Why do bigger galaxies have bigger black holes? (5 min)
- Lesson 248: Why do some galaxies have a bar? (5 min)
- Lesson 249: How do ring galaxies form? (5 min)
- Lesson 250: What is an active galaxy? (5 min)
- Lesson 251: What are ultra-diffuse galaxies? (5 min)
- Lesson 252: What happens where the solar wind meets Earth's magnetic field? (5 min)
- Lesson 253: Why do sunspots come in pairs? (5 min)
- Lesson 254: How do we see the far side of the Sun? (5 min)
- Lesson 255: How was Neptune found with mathematics? (5 min)
- Lesson 256: How do we spot a new asteroid? (5 min)
- Lesson 257: Why does sunlight make some asteroids spin faster? (5 min)
- Lesson 258: Why do Martian dust storms sometimes cover the whole planet? (5 min)
- Lesson 259: How do we weigh a planet that has no moon? (5 min)
- Lesson 260: Why is the air on Venus so thick? (5 min)
- Lesson 261: Why does the Moon have almost no air? (5 min)
- Lesson 262: Why does a rocket roll after liftoff? (5 min)
- Lesson 263: How does a rocket engine keep from melting? (5 min)
- Lesson 264: Why do launches get scrubbed for weather? (5 min)
- Lesson 265: How does aerobraking save fuel? (5 min)
- Lesson 266: How do satellites know which way they point? (5 min)
- Lesson 267: How can a satellite talk straight to your phone? (5 min)
- Lesson 268: How does a satellite spot lightning from space? (5 min)
- Lesson 269: How does a satellite measure wet soil? (5 min)
- Lesson 270: How does a spacecraft inspect a dead rocket stage up close? (5 min)
- Lesson 271: Why is the Arctic warming faster than the rest of Earth? (5 min)
- Lesson 272: Why do some weather patterns get stuck for days? (5 min)
- Lesson 273: How does a satellite measure sea ice thickness? (5 min)
- Lesson 274: Why does a supernova fade so slowly? (5 min)
- Lesson 275: How did giant planets end up so close to their stars? (5 min)
- Lesson 276: How does a coronagraph hide a star's glare? (5 min)
- Lesson 277: How do you catch a neutrino in the ice or the sea? (5 min)
- Lesson 278: How do clouds both warm and cool the planet? (5 min)
- Lesson 279: Why do moonquakes ring for so long? (5 min)
- Lesson 280: Why does a gravitational wave chirp rise in pitch? (5 min)
- Lesson 281: Can merging black holes kick the new one out? (5 min)
- Lesson 282: How does dust make stars look redder? (5 min)
- Lesson 283: Can an exploding star trigger new stars? (5 min)
- Lesson 284: How do molecules form in freezing space? (5 min)
- Lesson 285: Why do some young stars suddenly brighten for years? (5 min)
- Lesson 286: How does an ice core record ancient air? (5 min)
- Lesson 287: Why is the Milky Way's disk warped? (5 min)
- Lesson 288: Why do some solar storms hit hard and others fizzle? (5 min)
- Lesson 289: What holds a solar prominence up? (5 min)
- Lesson 290: Why do the Sun's fastest particles reach Earth in minutes? (5 min)
- Lesson 291: Why do comets break apart? (5 min)
- Lesson 292: Why is Phobos slowly falling toward Mars? (5 min)
- Lesson 293: What pushes water up through an ice volcano? (5 min)
- Lesson 294: How did Arrokoth end up as two joined lumps? (5 min)
- Lesson 295: How do parachutes slow a returning capsule? (5 min)
- Lesson 296: How does a rocket engine restart in weightlessness? (5 min)
- Lesson 297: How does a rotating detonation engine work? (5 min)
- Lesson 298: Why must rocket fuel stay so cold, and what does it lose in space? (5 min)
- Lesson 299: Why do some Moon craters have bright rays? (5 min)
- Lesson 300: Why does the Moon rise so far north and south every 18.6 years? (5 min)

## Advanced (216 lessons)

- Lesson 1: Why the TV satellite hangs at 36,000 km (6 min)
- Lesson 2: How fast the sky turns (6 min)
- Lesson 3: The coincidence that makes total eclipses (6 min)
- Lesson 4: What it costs to reach the Moon (6 min)
- Lesson 5: How far away was the quake? (6 min)
- Lesson 6: Why a small bolt is dangerous (6 min)
- Lesson 7: Your latitude is written in the sky (6 min)
- Lesson 8: How much warning does the Sun give? (6 min)
- Lesson 9: How can you work out a planet's year from its distance? (6 min)
- Lesson 10: How fast must you go to leave the Moon, Mars or Jupiter? (6 min)
- Lesson 11: How much stronger is a magnitude 7 earthquake than a magnitude 5? (6 min)
- Lesson 12: How do slow changes in Earth's orbit pace the ice ages? (6 min)
- Lesson 13: How much more light does a telescope collect than your eye? (6 min)
- Lesson 14: How old is the light you are looking at? (6 min)
- Lesson 15: How many Earths would fit inside the Sun? (6 min)
- Lesson 16: How much would you weigh on the Moon and on Mars? (6 min)
- Lesson 17: How far can you see from the space station? (6 min)
- Lesson 18: How much sunlight reaches Mars? (6 min)
- Lesson 19: How far has the Moon moved away during your lifetime? (6 min)
- Lesson 20: How do astronomers measure the distance to a star? (6 min)
- Lesson 21: How fast does Earth's spin carry you? (6 min)
- Lesson 22: Sun or Moon: which raises the bigger tide? (6 min)
- Lesson 23: How strong is gravity on Saturn? (6 min)
- Lesson 24: How big does Earth look from the Moon? (6 min)
- Lesson 25: How much brighter is a first magnitude star? (6 min)
- Lesson 26: How much fuel does a rocket need? (6 min)
- Lesson 27: How long does a sunset take? (6 min)
- Lesson 28: How far away was that lightning? (6 min)
- Lesson 29: How deep is the ocean under a tsunami? (6 min)
- Lesson 30: How far have you travelled around the Sun? (6 min)
- Lesson 31: How deep is a planet's shadow on its star? (6 min)
- Lesson 32: Why did satellite internet feel slow? (6 min)
- Lesson 33: Why does GPS need Einstein? (6 min)
- Lesson 34: How long are shadows at the Moon's pole? (6 min)
- Lesson 35: How fast does an interstellar comet cross our neighbourhood? (6 min)
- Lesson 36: Why must we nudge an asteroid early? (6 min)
- Lesson 37: Why does LIGO have two detectors? (6 min)
- Lesson 38: How big is a black hole? (6 min)
- Lesson 39: How many times has the Sun circled the galaxy? (6 min)
- Lesson 40: How much power has Voyager lost? (6 min)
- Lesson 41: How much bone does an astronaut lose? (6 min)
- Lesson 42: How close to the Big Bang can Webb see? (6 min)
- Lesson 43: Why does the Sun's equator outrun its poles? (6 min)
- Lesson 44: How bright will the Blaze Star get? (6 min)
- Lesson 45: How much space dust lands on Earth each second? (6 min)
- Lesson 46: How much of the sky will Euclid map? (6 min)
- Lesson 47: How much data does the Rubin Observatory collect? (6 min)
- Lesson 48: Why does Venus spin slower than it orbits? (6 min)
- Lesson 49: How fast can a gentle push make a spacecraft? (6 min)
- Lesson 50: Why is coming home from the Moon so hot? (6 min)
- Lesson 51: How long until a day lasts 25 hours? (6 min)
- Lesson 52: How much water is in the stratosphere? (6 min)
- Lesson 53: How far had the tsunami travelled? (6 min)
- Lesson 54: How many more boosts at solar maximum? (6 min)
- Lesson 55: How fast is the night sky doubling in brightness? (6 min)
- Lesson 56: How long would Andromeda take to reach us? (6 min)
- Lesson 57: How deep is the Sun when the zodiacal light appears? (6 min)
- Lesson 58: How far away can you see a red aurora? (6 min)
- Lesson 59: How close to the Sun did Parker fly? (6 min)
- Lesson 60: How big does the Sun look from Mars? (6 min)
- Lesson 61: How much extra Moon does libration show? (6 min)
- Lesson 62: How fast does the Moon move around Earth? (6 min)
- Lesson 63: How long does a radio call take to reach the Moon? (6 min)
- Lesson 64: How much Moon soil holds a litre of water? (6 min)
- Lesson 65: Why did Blue Ghost last about two weeks? (6 min)
- Lesson 66: How hard does the air push at Max Q? (6 min)
- Lesson 67: How fast does the launch pad flood? (6 min)
- Lesson 68: How hard does a Mars lander brake? (6 min)
- Lesson 69: How far was Mars when Perseverance landed? (6 min)
- Lesson 70: How many Earths away did Artemis II fly? (6 min)
- Lesson 71: How much does melting ice raise the sea? (6 min)
- Lesson 72: How much extra energy is Earth keeping? (6 min)
- Lesson 73: How small a detail could Hubble see on Earth? (6 min)
- Lesson 74: How hard does Jupiter tug the Sun? (6 min)
- Lesson 75: How far does the Sun bend starlight? (6 min)
- Lesson 76: How much mass does the Sun lose every second? (6 min)
- Lesson 77: How can Io weigh Jupiter? (6 min)
- Lesson 78: How did Io reveal the speed of light? (6 min)
- Lesson 79: How hard did a meteoroid hit the Moon? (6 min)
- Lesson 80: How fast does SLS accelerate at liftoff? (6 min)
- Lesson 81: When could carbon dioxide double? (6 min)
- Lesson 82: How much Arctic summer ice is missing? (6 min)
- Lesson 83: How much air is missing above a hurricane's eye? (6 min)
- Lesson 84: How fast does Landsat fly? (6 min)
- Lesson 85: How hard does oxygen push inside a spacesuit? (6 min)
- Lesson 86: How much does a gravitational wave stretch LIGO? (6 min)
- Lesson 87: Where is the habitable zone of TRAPPIST-1? (6 min)
- Lesson 88: How many galaxies are in the sky? (6 min)
- Lesson 89: How fast does Barnard's Star move sideways? (6 min)
- Lesson 90: How long would Voyager 1 take to reach the nearest star? (6 min)
- Lesson 91: How much stronger is an X-class solar flare? (6 min)
- Lesson 92: How far off was the old length of a day on Uranus? (6 min)
- Lesson 93: How fast did Ingenuity's blade tips move? (6 min)
- Lesson 94: How deep would you dive to feel Venus's air pressure? (6 min)
- Lesson 95: How fast does sunrise sweep across the Moon? (6 min)
- Lesson 96: Does the Moon really circle Earth's centre? (6 min)
- Lesson 97: How dense is the Moon? (6 min)
- Lesson 98: How hard does Orion hit the ocean? (6 min)
- Lesson 99: How hard would Orion's escape motor pull the crew? (6 min)
- Lesson 100: Which weighs more in SLS: hydrogen or oxygen? (6 min)
- Lesson 101: How many night sonic booms would Starship bring to Florida? (6 min)
- Lesson 102: How big must a solar power satellite be for a gigawatt? (6 min)
- Lesson 103: How fast could microbes grow on a Ryugu grain? (6 min)
- Lesson 104: What does each SLS mission really cost? (6 min)
- Lesson 105: What does each working Moon lander cost NASA? (6 min)
- Lesson 106: How many short stays would replace the space station? (6 min)
- Lesson 107: How soon could rocket soot grow tenfold? (6 min)
- Lesson 108: What power price would make data centres in orbit pay? (6 min)
- Lesson 109: How warm must late 2026 be to beat the record? (6 min)
- Lesson 110: When will the Southern Ocean turn corrosive to shells? (6 min)
- Lesson 111: How much speed does it take to climb to a geostationary orbit? (6 min)
- Lesson 112: How long is a geostationary satellite's night? (6 min)
- Lesson 113: How long does a picture take to come home from Mars? (6 min)
- Lesson 114: How many days does Sentinel-2 need to photograph all of Earth? (6 min)
- Lesson 115: How much faster does a drag sail bring a satellite down? (6 min)
- Lesson 116: How crowded is low Earth orbit? (6 min)
- Lesson 117: How much energy does a hurricane release? (6 min)
- Lesson 118: How much water does an atmospheric river carry? (6 min)
- Lesson 119: How old is the universe, judged by its expansion rate? (6 min)
- Lesson 120: How much has the universe stretched since the afterglow was released? (6 min)
- Lesson 121: How much heavier is the Coma Cluster than its stars? (6 min)
- Lesson 122: How big is Betelgeuse? (6 min)
- Lesson 123: How hot is a star, judged by its colour? (6 min)
- Lesson 124: How fluffy can a planet be? (6 min)
- Lesson 125: How much sharper will the ELT see than Webb? (6 min)
- Lesson 126: How much energy does a sand-grain meteor carry? (6 min)
- Lesson 127: How much energy did the clearest gravitational wave carry? (6 min)
- Lesson 128: How fast does the edge of the fastest pulsar move? (6 min)
- Lesson 129: How many Suns a day does the brightest quasar eat? (6 min)
- Lesson 130: How old is the Crab Nebula, judged by how fast it grows? (6 min)
- Lesson 131: How old is the Ring Nebula? (6 min)
- Lesson 132: How much does a glowing nebula weigh? (6 min)
- Lesson 133: How far apart are the stars in a globular cluster's core? (6 min)
- Lesson 134: How long will the Milky Way's gas last? (6 min)
- Lesson 135: How heavy must the Galaxy be to hold the Sun in orbit? (6 min)
- Lesson 136: How strong is a sunspot's magnet? (6 min)
- Lesson 137: How much energy does a coronal mass ejection carry? (6 min)
- Lesson 138: How much does the Sun's brightness change over a cycle? (6 min)
- Lesson 139: Do Enceladus's plumes escape into space? (6 min)
- Lesson 140: How long did Huygens fall to Titan? (6 min)
- Lesson 141: How often do Io, Europa and Ganymede line up? (6 min)
- Lesson 142: How much water is in Ganymede's ocean? (6 min)
- Lesson 143: How much heat does Io give off? (6 min)
- Lesson 144: How big does Charon look in Pluto's sky? (6 min)
- Lesson 145: How thin are Saturn's rings? (6 min)
- Lesson 146: How fast does Mercury's orbit turn? (6 min)
- Lesson 147: Could all the planets fit between Earth and the Moon? (6 min)
- Lesson 148: How long is the trip to Mars on the cheapest path? (6 min)
- Lesson 149: How many more satellites does a lower shell need? (6 min)
- Lesson 150: How much sky glow does a dimmed white streetlight make? (6 min)
- Lesson 151: How many years of images would Betelgeuse's companion need? (6 min)
- Lesson 152: How long can a disk in a harsh star nursery keep its gas? (6 min)
- Lesson 153: How old would Saturn's rings be if they kept less dust? (6 min)
- Lesson 154: How many sunrises does the space station see each day? (6 min)
- Lesson 155: How many satellites are above your horizon right now? (6 min)
- Lesson 156: How much does Earth weigh? (6 min)
- Lesson 157: How big is Proxima Centauri? (6 min)
- Lesson 158: How hot is a lava planet? (6 min)
- Lesson 159: How far away could you see a candle? (6 min)
- Lesson 160: How big is the shadow of the Milky Way's black hole? (6 min)
- Lesson 161: How far apart are galaxies compared with their size? (6 min)
- Lesson 162: How long would it take to fall into the Sun? (6 min)
- Lesson 163: How fast do the clouds on Jupiter's equator move? (6 min)
- Lesson 164: When will Halley's Comet come back? (6 min)
- Lesson 165: How big would Jupiter's magnetic bubble look in our sky? (6 min)
- Lesson 166: How much radiation does a trip around the Moon give? (6 min)
- Lesson 167: How much does the space station sink each day? (6 min)
- Lesson 168: How much water does the space station recycle in a year? (6 min)
- Lesson 169: How many pieces does one collision in orbit make? (6 min)
- Lesson 170: How fast does a debris cloud spread around its orbit? (6 min)
- Lesson 171: How deep is the ocean on average, worked out from its volume? (6 min)
- Lesson 172: How much does Earth's air weigh? (6 min)
- Lesson 173: How cold would Earth be without the greenhouse effect? (6 min)
- Lesson 174: How far apart are two stars in the sky, from their coordinates? (6 min)
- Lesson 175: How much would you weigh on a neutron star? (6 min)
- Lesson 176: How heavy is the Milky Way's black hole, worked out from star S2's orbit? (6 min)
- Lesson 177: How much slower does time run at a neutron star's surface? (6 min)
- Lesson 178: How quickly does the Crab pulsar slow down? (6 min)
- Lesson 179: How fast does gas orbit right next to the Milky Way's black hole? (6 min)
- Lesson 180: How many star clusters like the one in Orion does the Milky Way make? (6 min)
- Lesson 181: How far is a planetary nebula, worked out from how fast it grows? (6 min)
- Lesson 182: How many Suns' worth of stars could the Carina Nebula's gas make? (6 min)
- Lesson 183: How far is a galaxy, worked out from how fast it moves away? (6 min)
- Lesson 184: How big is the Andromeda Galaxy really, from how wide it looks? (6 min)
- Lesson 185: How fast would a galaxy's outer stars move without dark matter? (6 min)
- Lesson 186: Has the Sun's loss of mass moved the planets? (6 min)
- Lesson 187: How much extra heat does Uranus give off? (6 min)
- Lesson 188: How big a moon would Saturn's rings make if squeezed together? (6 min)
- Lesson 189: How fast will Apophis fly past Earth in 2029? (6 min)
- Lesson 190: How fast is asteroid Bennu spinning up? (6 min)
- Lesson 191: When does a reusable rocket pay off? (6 min)
- Lesson 192: How many tonnes of carbon dioxide are in Earth's air? (6 min)
- Lesson 193: How long did the Tonga pressure wave take to circle the globe? (6 min)
- Lesson 194: How much fainter is an Earth twin than its star? (6 min)
- Lesson 195: How fast were two neutron stars circling just before they merged? (6 min)
- Lesson 196: How much dark matter is inside Earth's volume? (6 min)
- Lesson 197: What share of the Sun's light does Earth catch? (6 min)
- Lesson 198: How much closer did DART push Dimorphos to its partner? (6 min)
- Lesson 199: How much faster is Halley's Comet near the Sun than far out? (6 min)
- Lesson 200: How old is the trail of a young star's jet? (6 min)
- Lesson 201: How much carbon dioxide does a station crew breathe out in a year? (6 min)
- Lesson 202: How heavy must Omega Centauri's black hole be to keep its fastest stars? (6 min)
- Lesson 203: How fast is the Hulse-Taylor pulsar's orbit shrinking? (6 min)
- Lesson 204: How far is V838 Monocerotis, worked out from its light echo? (6 min)
- Lesson 205: How many solar neutrinos pass through a square centimetre each second? (6 min)
- Lesson 206: How many Earths could the May 2024 sunspot group hold? (6 min)
- Lesson 207: How much brighter is a full Earth from the Moon than a full Moon from Earth? (6 min)
- Lesson 208: Lifting 1 kg to the space station or speeding it up: which costs more? (6 min)
- Lesson 209: How fast can sunlight speed up a solar sail? (6 min)
- Lesson 210: Can the Crab pulsar's slowdown power the whole nebula? (6 min)
- Lesson 211: How fast is Phobos falling toward Mars, and when will it break up? (6 min)
- Lesson 212: How many supernovae would it take to blow the Fermi bubbles? (6 min)
- Lesson 213: How long would one lap of the Moon take at Artemis II's closest height? (6 min)
- Lesson 214: What share of Earth twins line up to cross their star? (6 min)
- Lesson 215: How long does the Great Red Spot take to spin once? (6 min)
- Lesson 216: How much faster do Saturn's inner rings orbit than its outer rings? (6 min)

## Expert (122 lessons)

- Lesson 1: Will you see the aurora tonight? (7 min)
- Lesson 2: How long does the junk stay up? (7 min)
- Lesson 3: Will you see the space station tonight? (7 min)
- Lesson 4: Briefing before the next real launch (7 min)
- Lesson 5: A big earthquake just struck: what do we know in the first hour? (7 min)
- Lesson 6: Where will the falling rocket stage come down? (7 min)
- Lesson 7: Moon, planet or faint galaxy: what is tonight good for? (7 min)
- Lesson 8: Will you see the Andromeda galaxy from your balcony? (7 min)
- Lesson 9: A solar eclipse is coming: will you see it from home? (7 min)
- Lesson 10: Take a headline apart: how fast is the Milky Way really moving? (7 min)
- Lesson 11: Is tonight's meteor shower worth going out for? (7 min)
- Lesson 12: A solar storm is coming: what really threatens you? (7 min)
- Lesson 13: An asteroid will "skim past Earth": should you worry? (7 min)
- Lesson 14: A hurricane on the map: how do you read the forecast cone? (7 min)
- Lesson 15: A lunar eclipse is coming: when should you set the alarm? (7 min)
- Lesson 16: A volcano erupts: will your flight be cancelled? (7 min)
- Lesson 17: After a tsunami: when is it safe to go back to the beach? (7 min)
- Lesson 18: A Webb picture: what do its colours mean? (7 min)
- Lesson 19: "Betelgeuse is about to explode": what does soon mean? (7 min)
- Lesson 20: Supermoon tonight: is it worth waking up for? (7 min)
- Lesson 21: After a big earthquake: are the aftershocks over? (7 min)
- Lesson 22: Will a solar-powered lander outlast the Martian dust? (7 min)
- Lesson 23: A solar radiation storm: will your polar flight change? (7 min)
- Lesson 24: A comet in the headlines: when should you look? (7 min)
- Lesson 25: Wildfire smoke on the map: will it reach you? (7 min)
- Lesson 26: Only a Category 1 hurricane: is it safe to stay? (7 min)
- Lesson 27: "A big earthquake next week": should you believe it? (7 min)
- Lesson 28: You found a strange rock: is it a meteorite? (7 min)
- Lesson 29: Mars behind the Sun: should you send the rovers commands? (7 min)
- Lesson 30: An earthquake alert on your phone: how long do you have? (7 min)
- Lesson 31: "Signs of life on K2-18b": should you believe it? (7 min)
- Lesson 32: An asteroid with a 1 in 32 chance: should you panic? (7 min)
- Lesson 33: Your phone puts you in the river: what went wrong? (7 min)
- Lesson 34: Why does the Moon need its own time? (7 min)
- Lesson 35: An ocean under Mars: can astronauts drink it? (7 min)
- Lesson 36: A trip to Mars: how much radiation would the crew get? (7 min)
- Lesson 37: The space station will come down: where, and is it dangerous? (7 min)
- Lesson 38: A gravitational wave alert: should you grab a telescope? (7 min)
- Lesson 39: Is 3I/ATLAS an alien probe? How to check (7 min)
- Lesson 40: A Moon base: sunlight or a nuclear reactor? (7 min)
- Lesson 41: Moon or Mars first: where should astronauts go next? (7 min)
- Lesson 42: Return to Venus: why go back to the hottest planet? (7 min)
- Lesson 43: Starliner: when should you not fly home in your own ship? (7 min)
- Lesson 44: Mars Sample Return was cancelled: what now for the samples? (7 min)
- Lesson 45: Rubin sends millions of alerts a night: which should you follow? (7 min)
- Lesson 46: Can Europa Clipper find life? (7 min)
- Lesson 47: Why do Moon landers keep tipping over? (7 min)
- Lesson 48: Dragonfly on Titan: why send a drone? (7 min)
- Lesson 49: The Hubble tension: which measurement should you trust? (7 min)
- Lesson 50: Who owns the Moon? (7 min)
- Lesson 51: A 2028 Moon landing: can the refuelling be ready? (7 min)
- Lesson 52: Nuclear rockets for Mars: is twice as efficient worth it? (7 min)
- Lesson 53: Mars probes ready early: launch now, or wait on the ground? (7 min)
- Lesson 54: After Artemis II: is Orion's heat shield ready for the next crew? (7 min)
- Lesson 55: A geostationary satellite: launch from Kourou or Florida? (7 min)
- Lesson 56: The first south pole landing: which kind of site? (7 min)
- Lesson 57: Chang'e 6: was a far side sample mission worth it? (7 min)
- Lesson 58: A Moon base by a young fault: is the quake risk acceptable? (7 min)
- Lesson 59: Does Artemis need a station around the Moon? (7 min)
- Lesson 60: A radio telescope on the Moon's far side: why go so far? (7 min)
- Lesson 61: The Sun passed its peak: is aurora season over? (7 min)
- Lesson 62: An eclipse made by two spacecraft: why not one? (7 min)
- Lesson 63: A potential biosignature on Mars: life or not? (7 min)
- Lesson 64: Bennu's sample: did life's ingredients come from space? (7 min)
- Lesson 65: A mission to Uranus: why does the launch date matter so much? (7 min)
- Lesson 66: Satellite trails in space telescope pictures: limit or adapt? (7 min)
- Lesson 67: Is dark energy weakening: rewrite cosmology now, or wait? (7 min)
- Lesson 68: Roman launched: why a wide telescope when we have Hubble and Webb? (7 min)
- Lesson 69: Burning up old satellites: is it harmless? (7 min)
- Lesson 70: The leap second: drop it or keep it? (7 min)
- Lesson 71: 2024 passed 1.5 °C: is the Paris limit already broken? (7 min)
- Lesson 72: Your city is sinking: plan for the sea or the land? (7 min)
- Lesson 73: Space junk keeps growing: remove it, or just stop making it? (7 min)
- Lesson 74: Satellites leak radio noise: should the rules cover it? (7 min)
- Lesson 75: Does TRAPPIST-1e have air: is more Webb time worth it? (7 min)
- Lesson 76: Gaia DR4 is coming: wait, or publish with DR3? (7 min)
- Lesson 77: Planet Nine: is a Rubin search worth it? (7 min)
- Lesson 78: A lander near Apollo 11: how far is far enough? (7 min)
- Lesson 79: Antarctic sea ice near record lows: a new normal? (7 min)
- Lesson 80: Fewer weather balloons: will forecasts get worse? (7 min)
- Lesson 81: Land is drying: should sea-level plans count land water? (7 min)
- Lesson 82: GPS jammed over Europe: keep the old radio beacons? (7 min)
- Lesson 83: Habitable Worlds Observatory: is a 6 metre mirror big enough? (7 min)
- Lesson 84: Rocky planets with air: which one should Webb test next? (7 min)
- Lesson 85: NEO Surveyor: should NASA plan for a longer survey? (7 min)
- Lesson 86: A Carrington-class storm: should grids stock spare transformers? (7 min)
- Lesson 87: Oxygen from Moon rock: make it there or ship it? (7 min)
- Lesson 88: Earth's GPS at the Moon: use it, or build lunar satellites? (7 min)
- Lesson 89: Campi Flegrei keeps rising: evacuate now, or wait? (7 min)
- Lesson 90: Einstein Telescope: a triangle or two Ls? (7 min)
- Lesson 91: Thwaites Glacier: should coasts plan for the worst case? (7 min)
- Lesson 92: Coral reefs bleach every few years: can they still recover? (7 min)
- Lesson 93: An ice-free Arctic: should shipping plan for the polar route? (7 min)
- Lesson 94: Venice's flood barrier: will it cope as the sea rises? (7 min)
- Lesson 95: Lake Mead keeps falling: should the West plan for the 1,000-foot line? (7 min)
- Lesson 96: Swiss glaciers are melting fast: will the ice outlast this century? (7 min)
- Lesson 97: Five years to leave orbit: is a stricter rule the fix for space debris? (7 min)
- Lesson 98: A US Moon landing in 2028: how much delay can it afford? (7 min)
- Lesson 99: Istanbul's next big quake: even odds within a building's life? (7 min)
- Lesson 100: A six-month LIGO run: will it catch a neutron star merger? (7 min)
- Lesson 101: A Mars link: switch from radio to laser? (7 min)
- Lesson 102: Methane satellites: how often must a small fleet revisit? (7 min)
- Lesson 103: A "planet parade" headline: how many will you really see? (7 min)
- Lesson 104: A nearby supernova: how close would be dangerous? (7 min)
- Lesson 105: After CMB-S4: can other telescopes still find inflation's trace? (7 min)
- Lesson 106: Dark matter detectors found nothing: build bigger ones? (7 min)
- Lesson 107: Where did the gold come from: kilonovas or magnetars? (7 min)
- Lesson 108: Little red dots: how heavy is the cocooned black hole? (7 min)
- Lesson 109: The Sun's siblings: can chemistry pick them out? (7 min)
- Lesson 110: A gap in a young star's disk: worth hunting for a planet? (7 min)
- Lesson 111: Too many big early galaxies: does the theory need fixing? (7 min)
- Lesson 112: A CME is on its way: should you act on the arrival forecast? (7 min)
- Lesson 113: Power beyond Jupiter: plutonium or solar panels? (7 min)
- Lesson 114: One Voyager flyby in 1986: how far should we trust it? (7 min)
- Lesson 115: Land on Europa, if the ice is tens of kilometres thick? (7 min)
- Lesson 116: Titan without an ocean: change the search plans? (7 min)
- Lesson 117: Io without a shallow magma ocean: what drives its volcanoes? (7 min)
- Lesson 118: Phosphine on Venus: is the life clue dead? (7 min)
- Lesson 119: The Orion Nebula's distance: radio or Gaia? (7 min)
- Lesson 120: A Moon base: in a cave or on the surface? (7 min)
- Lesson 121: A radio dish in space for black hole pictures: worth it? (7 min)
- Lesson 122: Juno found more water than the Galileo probe: which to trust? (7 min)

## Related

- [All lessons](https://spacesphere.sygnito.com/en/learn/lessons)
- [Orbit Daily](https://spacesphere.sygnito.com/en/daily)