WEBVTT - Is There a Dark Side of the Moon?

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<v Speaker 1>Welcome to Brainstuff, a production of iHeartRadio. Hey, brain Stuff,

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<v Speaker 1>Lauren vogelbaumb here. You've probably noticed that when you look

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<v Speaker 1>up at the Moon, you always see the same features.

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<v Speaker 1>You can see craters and patches of lighter and darker areas.

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<v Speaker 1>With a pair of binoculars or a telescope, you can

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<v Speaker 1>make out even more detail. But no matter how you

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<v Speaker 1>look at the moon, you're always seeing the same landscape.

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<v Speaker 1>But the Moon is a sphere. If we're only seeing

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<v Speaker 1>one hemisphere, then what's on the other side. This is

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<v Speaker 1>the so called dark side of the moon, the side

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<v Speaker 1>we never see because it always faces away from Earth.

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<v Speaker 1>For this reason, people also use the phrase the dark

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<v Speaker 1>side of the Moon to describe something mysterious or unknown.

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<v Speaker 1>This side of the Moon faces the cold, black, expansive space.

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<v Speaker 1>What could be on this side of the moon? And

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<v Speaker 1>is it really always dark? We actually know what it

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<v Speaker 1>looks like, and no, it is not permanently dark. We

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<v Speaker 1>have lots of images from various lunar missions, and in

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<v Speaker 1>nineteen sixty eight, astronauts aboard the Apollo eight spacecraft were

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<v Speaker 1>the first humans to set eyes on it in person.

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<v Speaker 1>But the popularity of the phrase means that there is

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<v Speaker 1>ample opportunity for people to jump to the wrong conclusion,

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<v Speaker 1>especially since we only ever see that one hemisphere, and

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<v Speaker 1>it's easy to misunderstand the cause of the phases of

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<v Speaker 1>the moon that we see from Earth. But mostly this

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<v Speaker 1>is a problem with terminology. The descriptor dark side suggests

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<v Speaker 1>that shadows perpetually cloak the surface of the side of

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<v Speaker 1>the Moon that faces away from us. It's fun to

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<v Speaker 1>imagine a dividing line between the light side and the

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<v Speaker 1>dark side, but that's not how it works. While it

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<v Speaker 1>is true that some part of the Moon is dark

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<v Speaker 1>at any particular or time, it's not always the same part.

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<v Speaker 1>That's because like Earth, the Moon rotates on its axis,

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<v Speaker 1>a meaning it has a daytime and a night time.

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<v Speaker 1>So if you were to set up camp on the

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<v Speaker 1>Moon and stay put, you would eventually see the sun

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<v Speaker 1>rise and fall. You'd experience both day and night. So

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<v Speaker 1>technically the moon does have a dark side at any

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<v Speaker 1>given moment, but it shifts. The dark side is the

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<v Speaker 1>part currently experiencing night. The side of the moon we

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<v Speaker 1>see is sometimes the day side, sometimes the night side,

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<v Speaker 1>and sometimes a bit of both. A more accurate term

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<v Speaker 1>to describe The side of the Moon that we always

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<v Speaker 1>see is the near side. The side opposite is the

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<v Speaker 1>far side. The near side will always be facing toward us,

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<v Speaker 1>and the far side will always face away. This is

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<v Speaker 1>true from anywhere on Earth. If you were to fly

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<v Speaker 1>from America to Australia or vice versa, you'd see the

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<v Speaker 1>same features that you're familiar with back home. But why

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<v Speaker 1>do we only ever see one side of the Moon

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<v Speaker 1>from Earth? Okay, it takes about twenty nine days for

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<v Speaker 1>the Moon to make one complete orbit around the Earth.

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<v Speaker 1>That's also how long it takes the Moon to make

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<v Speaker 1>one rotation on its axis. Because the Moon's rotation and

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<v Speaker 1>orbit take the same amount of time, we always see

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<v Speaker 1>the same face of the Moon no matter when we

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<v Speaker 1>look at it. The Moon just keeps spinning the same

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<v Speaker 1>side of itself toward us as it orbits around us.

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<v Speaker 1>This happens because of gravity. Earth's gravitational pull on the

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<v Speaker 1>Moon is so strong that our planets slowed the Moon's

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<v Speaker 1>rotation down to its current speed. Its rotational speed is

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<v Speaker 1>locked with the time that it takes to orbit the Earth. Interestingly,

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<v Speaker 1>the Moon is doing the same thing to the Earth,

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<v Speaker 1>just much slower because the pull of the Moon on

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<v Speaker 1>the Earth is much smaller, so if you've ever felt

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<v Speaker 1>like the days are getting longer, they are technically still.

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<v Speaker 1>In a few billion years, the Earth's rotation will match

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<v Speaker 1>the time it takes the Moon to orbit the Earth.

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<v Speaker 1>By that time, the Moon and the Earth will have

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<v Speaker 1>drifted apart from each other a little bit, which means

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<v Speaker 1>it'll take a little longer for the Moon to travel

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<v Speaker 1>around the Earth, to the tune of about forty days

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<v Speaker 1>or so, meaning that in the distant future, one Earth

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<v Speaker 1>day will equal forty of our current Earth days, or

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<v Speaker 1>about nine hundred and sixty hours. Once the Earth's rotation

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<v Speaker 1>matches the time it takes for the Moon to orbit

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<v Speaker 1>the Earth, the same side of the Earth will face

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<v Speaker 1>the Moon all the time. But okay, let's talk about

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<v Speaker 1>the phases of the moon. A common misconception about the

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<v Speaker 1>moon is that it appears as just a sliver sometimes

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<v Speaker 1>called a new moon, when the Earth is between the

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<v Speaker 1>Sun and the Moon, thus blocking the light from the

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<v Speaker 1>Sun and casting a shadow across the moon. But in reality,

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<v Speaker 1>during a new moon, the Moon is between the Sun

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<v Speaker 1>and the Earth. Imagine that you're in a room that's

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<v Speaker 1>dark except for one window that has sunlight shining into it,

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<v Speaker 1>and then someone walks between you and the window. You

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<v Speaker 1>would see the person in silhouette. They'd appear mostly shadowy,

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<v Speaker 1>but with a bright outline along their side facing the window.

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<v Speaker 1>That's exactly what a new moon is. A full moon,

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<v Speaker 1>in contrast, is when the Earth is between the Moon

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<v Speaker 1>and the sun. Going back to our example, imagine that

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<v Speaker 1>you're the person standing by the window. If you turn

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<v Speaker 1>to look into the room, anyone standing there would be

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<v Speaker 1>well illuminated. That's the same as us looking at a

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<v Speaker 1>full moon. But again, whether it's a full moon or

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<v Speaker 1>a new moon, you're still looking at the same side

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<v Speaker 1>of the moon, the near side. During a new moon,

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<v Speaker 1>you're looking at the near side during lunar night time,

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<v Speaker 1>and during a full moon you're looking at the near

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<v Speaker 1>sides version of noon. All of this being said, the

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<v Speaker 1>far side of the moon is still a little mysterious

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<v Speaker 1>because the Moon's bulk blocks radio signals to and from

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<v Speaker 1>the Earth from its far side. Engineers don't yet have

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<v Speaker 1>a good way for us to explore that far side.

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<v Speaker 1>In the future, we may see NASA and other organizations

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<v Speaker 1>build radio relay towers on the Moon's surface to make

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<v Speaker 1>exploration possible. Until then, we'll have to content ourselves with

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<v Speaker 1>being looney over the side that faces us. Today's episode

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<v Speaker 1>is based on the article what and Where is the

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<v Speaker 1>Dark Side of the Moon on HowStuffWorks dot com written

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<v Speaker 1>by Jonathan Strickland. Brain Stuff is production of iHeartRadio in

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<v Speaker 1>partnership with hostuffworks dot Com and is produced by Tyler

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<v Speaker 1>klang A. Four more podcasts my heart Radio, visit the

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<v Speaker 1>iHeartRadio app, Apple Podcasts, or wherever you listen to your

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<v Speaker 1>favorite shows.