Date: 18 May 2026
Topic: Science
Codebreakers are a fun way to build numeracy skills.
Phase 1: The Earth is Round (~350 BCE, Ancient Greece)
Around 350 BCE, the Greek philosopher Aristotle proved the Earth was a sphere using lunar eclipses. He noticed that when the Earth blocks the sun's light from reaching the moon, it always casts a perfectly round shadow. Only a 3D sphere can cast a circular shadow from every single angle.
Other clues agreed, like how ships sink hull-first over the horizon, and how different star constellations become visible when you travel north or south.
Phase 2: Shifting to the Sun (~1610 CE, Italy)
Nearly 2,000 years later, in 1610, Galileo Galilei used a telescope in Padua, Italy, to discover four moons orbiting Jupiter.
This discovery completely shattered the dominant belief of the time:
Geocentrism: The idea that Earth ("Geo") is the stationary center of the universe and everything revolves around it.
Heliocentrism: The model where the Sun ("Helio") is at the center, and Earth is just another orbiting planet.
Finding moons around Jupiter proved that things could orbit a body other than Earth.