Here's why:

* Tidal Locking: The Moon is tidally locked to Earth, meaning it rotates at the same rate it orbits us. This means the same side of the Moon always faces Earth.

* "Dark Side" is a Misnomer: The term "dark side" is misleading. While it's not always illuminated by the Sun from our perspective, it receives just as much sunlight as the side we see. It's more accurately called the "far side" of the Moon.

So, how do we see the far side of the Moon?

* Spacecraft: We've seen the far side of the Moon thanks to spacecraft that have orbited it, like the Apollo missions and Lunar Reconnaissance Orbiter.

* Lunar Eclipses: During a lunar eclipse, the Earth blocks the Sun's light, casting a shadow on the Moon. This allows us to see a faint, reddish outline of the entire Moon, including the far side.

In summary: While we can't see the far side of the Moon from Earth, it's not truly "dark." It receives sunlight and has been extensively explored by spacecraft.