Synchronous Rotation of the Moon

Why does the same side of the Moon always face the Earth? The Moon has synchronous rotation: it's rotation period is the same as its period of revolution.

Earth image credit: NASA

Category:

Science & Technology

Tags:

• Moon
• astronomy
• synchronous rotation
• introductory astronomy

[reddiance1]

Excellent animation! I could never understand this before until I saw your animation. Good work !

[StonesDunedin]

@rg0057 Pretend that you are on the far side of the moon. You would see the whole 360 deg. of the sky every 29.5 of our days, since that's how long the moon takes to orbit the Earth. Why? Because over millions of years the Earth's gravity has slowed down the moon's rotation until it is 'locked' - as if there is a *long rope tying the 2 together.

[cocoalrose]

@techsta72 There are craters on Earth, like the one in the desert in Arizona. The earth probably was hit at the same time as the moon, likely millions upon millions of years ago. The solar system was a lot more violent back then; everything was still changing. Now, it's more balanced out. It has a rhythm to it that it was still developing when the moon and Earth were bombarded with meteors.

[solstice68]

We do a good job fooling ourselves and each other into thinking we can explain and understand such things as the universe, devinity, spirituality etc. Some very smart people even get rich off of some very stupid people regarding these topics. All we can do is keep observing and contmeplating. Don't take conventional wisdom as all truth. I look at the moon outside my window often and notice the alignment of the craters is not consistent with a round object that supposedly rotates on it's axis.

[small0but0mighty]

I have a test tomorrow:(

[techsta72]

Why do we see craters on the moon? If the side we see is always facing us then how did it get bombarded by meteorites? Did they pass through the earths atmosphere or very close to the earth? In that case why didn't the earth receive the impact as it has a stronger gravity pull. Just as jupiter consumes most of the meteorites in the solar system protecting the earth, i would think the earth would do the same to the moon? Does that make any sense????

[webhutspain]

Intelligently Designed.

[rockync7]

i dont think the moon rotates at all

[malmquist90]

Great job man thank you!

[popple73]

@lceus It hasn't always been like that. Millions of years ago, the Moon was closer to the Earth, and was spinning at a different speed. Over the years, the Earth momentum was slowly transferred to the Moon, which pushed it away and changed its speed, until it reached this equilibrium.

Well actually, equilibrium isn't reached yet. The Earth still slows down a bit (like 0,02 second a year or something) because of those tidal forces, and will continue until they both have the same period.

[lceus]

This is a bit too convenient, don't you think? My theory is that the moon is deadlocked to which side faces the earth because of magnetism. Sure, the moon's core might not be that hot anymore, but it's possible that one side of the moon is especially attracted to the magnet within the earth.