Astronomy & Space questions
86 fact-checked questions — tap any to predict the answer, then read why.
- The Sun is cooler than the proton barrier suggests. Why does fusion still start?
- Earth's atmosphere slowly leaks to space. Which gas escapes fastest?
- Why is Earth's day getting slightly longer every century?
- Why was Earth's day stuck at 19.5 hours for 1.5 billion years?
- Why might several small units beat one giant Moon reactor?
- Why is fission likelier than fusion for first Moon bases?
- Why put a lunar reactor away from the habitat?
- Why can a small reactor do jobs a radioisotope power source cannot?
- Why are Stirling or Brayton systems vital in Moon reactors?
- Why is waste heat a big Moon-engineering problem?
- Why are reactors attractive near shadowed lunar craters?
- Why is solar-only power hard for a lunar base?
- Why does the Moon look huge near the horizon?
- Why can the Moon be visible in the daytime?
- Why won't April's 'Pink Moon' actually look pink?
- Why does a spacecraft lose direct signal behind the Moon?
- Why does Artemis II practice building a radiation shelter onboard?
- Why does Artemis II record observations in real time during lunar flyby?
- Why does Artemis II review lunar targets right before the flyby?
- Why does Artemis II test water, toilet, and CO2 systems so early?
- Why does Artemis II use a free-return path around the Moon?
- Why does Artemis II fly near its separated upper stage?
- Why does Artemis II stay in Earth orbit for about a day before heading to the Moon?
- Why can we see distant galaxies?
- Why do stars die?
- Why are there asteroid belts?
- Why does gravity bend light?
- Why do some stars have planets?
- Why is the solar system flat?
- Why are exoplanets hard to see?
- Why does the ISS orbit Earth?
- Why is the universe expanding?
- Why can't stars fuse iron?
- Why does Pluto orbit differently?
- Why do white dwarfs exist?
- Why are some stars red and others blue?
- Why is light-year a distance?
- Why do supernovae occur?
- Why is a year on Earth 365 days?
- Why does the sun have sunspots?
- Why are nebulae colorful?
- Why do stars become red giants?
- Why are quasars so bright?
- Why is Neptune blue?
- Why are there time zones on Earth?
- Why do solar eclipses occur?
- How do spiral arms form in galaxies?
- Why is space cold if the sun is hot?
- Why do pulsars pulse?
- Why does Earth have one moon?
- Why do black holes form?
- Why can we see the Milky Way?
- Why is Venus hotter than Mercury?
- Why do planets stay in orbit?
- Why does the sun appear yellow?
- Why are there seasons on Earth?
- Why do meteor showers occur?
- Why does Jupiter have the Great Red Spot?
- Why don't satellites fall to Earth?
- Why do we always see the same moon face?
- Why do stars only appear at night?
- Why does the moon have phases?
- Why do planets appear to wander?
- Why can't we hear sounds in space?
- Why do astronauts float in space?
- Why does Saturn have rings?
- Why do black holes trap light?
- Why is Jupiter so big?
- Why do asteroids and meteors differ?
- Why does the Moon seem to change shape in the sky?
- Why don't we feel the Earth spinning?
- Why can we see the Moon during the day?
- Why can't we see stars during the day?
- Why are there craters on the Moon?
- Why do comets have tails?
- Why is Mars called the Red Planet?
- Why is Venus the hottest planet?
- Why does the Moon affect ocean tides?
- Why is the sunset colorful?
- Why do planets orbit the Sun?
- Why do stars twinkle but planets don't?
- How do eclipses occur?
- Why does a year have 365 days?
- Why do we have seasons?
- Why can we only see one side of the Moon?
- Why is space dark if stars are bright?