Space & Time

Short, surprising cards on space & time. Each one is labelled Established, Debated or Speculative, so you always know how solid the evidence is.

• A day on Venus is longer than its year.

  Established. Venus takes about 243 Earth days to spin once, but only 225 days to go around the Sun. It also spins backwards, so the Sun rises in the…

• The light from Andromeda left before humans existed.

  Established. On a dark night you can see the Andromeda galaxy with your bare eyes. That light set off around 2.5 million years ago, before our species…

• A spacecraft launched in 1977 is still sending messages from interstellar space.

  Established. Voyager 1 left Earth in 1977 and is now more than 24 billion kilometres away, the most distant human-made object. Its signal takes over 22…

• A teaspoon of neutron star would weigh about a billion tonnes.

  Established. When a giant star explodes, its core can collapse into a ball about 20 km across holding more mass than the Sun. Atoms are crushed together…

• The calcium in your bones was made inside a star.

  Established. The Big Bang made mostly hydrogen and helium. Almost every other element in your body, from the carbon in your cells to the iron in your…

• Saturn's rings might be younger than the dinosaurs.

  Debated. Data from the Cassini spacecraft suggested the rings are bright and clean, as if only 100 to 400 million years old. Saturn itself is 4.5…

• Mars has a volcano almost three times taller than Everest.

  Established. Olympus Mons rises about 22 km above the Martian plains. It is so wide, about 600 km, that if you stood on it the slope would vanish past…

• The Moon is drifting away from us, about as fast as your fingernails grow.

  Established. Apollo astronauts left mirrors on the Moon. By bouncing lasers off them, scientists measure that it moves about 3.8 cm further away each…

• About 95% of the universe is made of something we can't see.

  Established. Everything we can detect, every star, planet and person, makes up only about 5% of the universe. The rest is 'dark matter' and 'dark…

• It may rain diamonds on Neptune and Uranus.

  Debated. Deep inside these ice giants, crushing pressure may squeeze carbon into diamonds that sink like hail. Lab experiments have made tiny…

• In 2019, one of the brightest stars in the sky suddenly dimmed.

  Established. Betelgeuse, the red shoulder of Orion, lost more than half its brightness over a few months. People wondered if it was about to explode.…

• In 2017, an object from another star system flew past us.

  Debated. ʻOumuamua was the first object seen passing through our solar system from interstellar space. It was long, tumbling, and sped up slightly…

• Perfect eclipses happen because of a cosmic coincidence.

  Established. The Sun is about 400 times wider than the Moon, and also about 400 times further away. So from Earth they look almost exactly the same…

• The sunlight on your skin began its journey thousands of years ago.

  Established. Light takes about 8 minutes to reach us from the Sun's surface. But the energy was made in the core, and bouncing its way out through the…