Tidal Locking
Why do we always see the same side of the Moon? This is due to Synchronous Rotation. Over billions of years, Earth’s gravity exerted tidal forces on the Moon, slowing its rotation until it matched its orbital period.
Tidal Forces and Gravity
The Moon’s gravitational pull creates "bulges" in Earth’s oceans. As the Earth rotates through these bulges, we experience high and low tides.
[Image of lunar tides diagram]$F_t \approx \frac{2G M m d}{r^3}$
Where $M$ is the Moon's mass, $d$ is Earth's radius, and $r$ is the distance between them.
Regolith and Surface
Unlike Earth, the Moon has no atmosphere to protect it. Its surface is covered in Regolith—a fine, glass-like dust created by billions of years of meteorite impacts. These impacts are also responsible for the "Maria" (dark plains) which were once ancient volcanic lava flows.
The Giant Impact Hypothesis
The leading theory suggests the Moon formed approximately 4.5 billion years ago when a Mars-sized body named Theia collided with the early Earth. The debris from this collision coalesced in orbit to form the Moon.