Why Do We Always See the Same Side of the Moon?

moon
NASA/GSFC/LRO/Arizona State University
Q: Why does the moon always present the same face to us? I find it impossible to believe that this could happen by chance. — Michael Connelly, TorontoA: Nope, not by chance — it’s pure physics.For starters, the moon is not stuck in place with one side facing us. Our lunar companion rotates while it orbits Earth. It’s just that the amount of time it takes the moon to complete a revolution on its axis is the same it takes to circle our planet — about 27 days. As a result, the same lunar hemisphere always faces Earth.How’d this come to be? In a word: gravity. The moon’s gravity slightly warps our planet’s shape and gives us tides. Likewise, Earth tugs at the moon, creating a rocky, high-tide “bulge” facing us. That bulge ended up working like a brake, slowing the moon’s spin down to the current rate, so the lunar high tide permanently faces us.

When that happened, about 4 billion years ago, the moon became “tidally locked,” and it has presented us the same visage ever since.

http://discovermagazine.com/2014/dec/2-ask-discover#5465

If you wish you can Leave a Reply. We will publish it after moderation. Insults and Spam are automatically deleted. Thank you for visiting my blog today.

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: