Date: 31 May 2026
Topic: Science
Codebreakers are a fun way to build numeracy skills.
Theia struck Earth at an angle, rather than head-on. The impact probably knocked Earth's axis over, contributing to our 23.5° tilt, which gives us seasons.
The Moon was much closer then - perhaps only 20,000–30,000 km away compared with today's 384,000 km. The Moon is still moving away from Earth at about 3.8 cm per year due to tidal forces.
The Moon is made mostly of rock from Earth's outer layers, which helps explain why Moon rocks are chemically very similar to Earth rocks.
Many of the largest craters formed during a period called the Late Heavy Bombardment, about 4 billion years ago, when the young Solar System was full of leftover debris smashing into planets and moons.
The earth had lots of them too, however, on earth we have atmosphere so meteors usually burn up in the atmosphere. Plus, wind, rain, rivers, plants, glaciers, and tectonic activity gradually erase craters.
The chance of another Theia hitting us is essentially zero, as we don't have many lingering proto-planets lying around in the solar system. However, a rogue star passing through the outer Solar System would be a problem.
Not because it would hit us, but because it could disturb the Oort Cloud—a huge shell of icy bodies surrounding the Solar System.
That could send a swarm of comets toward the inner planets over millions of years.