Why Can't We See the Dark Side of The Moon?

One of the most important things we have learned about the Moon is that while it revolves around the Earth, it always points the same face toward our planet. That is the only face we see when we look at the Moon from home. In fact, we were only able to see the so-called dark side of the Moon for the first time in 1959, when we managed to get a spacecraft into a lunar orbit, allowing it to take pictures of the other side. Until then, there might as well have been cities and lakes there for all we knew.

This perfect positioning is only possible because the Moon takes exactly as long to revolve around the Earth as it does to rotate on its own axis. Thus, for every degree that it revolves on its orbit, it rotates the same amount on its axis, perpetually keeping the same face towards us.