1 00:00:01,840 --> 00:00:07,560 Speaker 1: Welcome to Brainstuff, a production of iHeartRadio. Hey, brain Stuff, 2 00:00:07,600 --> 00:00:12,360 Speaker 1: Lauren vogelbaumb here. You've probably noticed that when you look 3 00:00:12,400 --> 00:00:15,200 Speaker 1: up at the Moon, you always see the same features. 4 00:00:15,920 --> 00:00:19,840 Speaker 1: You can see craters and patches of lighter and darker areas. 5 00:00:20,400 --> 00:00:22,840 Speaker 1: With a pair of binoculars or a telescope, you can 6 00:00:22,880 --> 00:00:26,599 Speaker 1: make out even more detail. But no matter how you 7 00:00:26,640 --> 00:00:30,800 Speaker 1: look at the moon, you're always seeing the same landscape. 8 00:00:31,120 --> 00:00:34,159 Speaker 1: But the Moon is a sphere. If we're only seeing 9 00:00:34,320 --> 00:00:39,760 Speaker 1: one hemisphere, then what's on the other side. This is 10 00:00:39,800 --> 00:00:42,760 Speaker 1: the so called dark side of the moon, the side 11 00:00:42,800 --> 00:00:45,840 Speaker 1: we never see because it always faces away from Earth. 12 00:00:46,800 --> 00:00:49,080 Speaker 1: For this reason, people also use the phrase the dark 13 00:00:49,120 --> 00:00:52,199 Speaker 1: side of the Moon to describe something mysterious or unknown. 14 00:00:53,960 --> 00:00:57,760 Speaker 1: This side of the Moon faces the cold, black, expansive space. 15 00:00:58,520 --> 00:01:00,760 Speaker 1: What could be on this side of the moon? And 16 00:01:01,120 --> 00:01:06,160 Speaker 1: is it really always dark? We actually know what it 17 00:01:06,200 --> 00:01:09,800 Speaker 1: looks like, and no, it is not permanently dark. We 18 00:01:09,880 --> 00:01:13,120 Speaker 1: have lots of images from various lunar missions, and in 19 00:01:13,240 --> 00:01:16,720 Speaker 1: nineteen sixty eight, astronauts aboard the Apollo eight spacecraft were 20 00:01:16,760 --> 00:01:18,840 Speaker 1: the first humans to set eyes on it in person. 21 00:01:21,040 --> 00:01:23,399 Speaker 1: But the popularity of the phrase means that there is 22 00:01:23,480 --> 00:01:26,680 Speaker 1: ample opportunity for people to jump to the wrong conclusion, 23 00:01:27,240 --> 00:01:30,560 Speaker 1: especially since we only ever see that one hemisphere, and 24 00:01:30,680 --> 00:01:33,399 Speaker 1: it's easy to misunderstand the cause of the phases of 25 00:01:33,400 --> 00:01:36,800 Speaker 1: the moon that we see from Earth. But mostly this 26 00:01:36,920 --> 00:01:42,440 Speaker 1: is a problem with terminology. The descriptor dark side suggests 27 00:01:42,480 --> 00:01:45,880 Speaker 1: that shadows perpetually cloak the surface of the side of 28 00:01:45,880 --> 00:01:49,120 Speaker 1: the Moon that faces away from us. It's fun to 29 00:01:49,160 --> 00:01:52,280 Speaker 1: imagine a dividing line between the light side and the 30 00:01:52,360 --> 00:01:56,960 Speaker 1: dark side, but that's not how it works. While it 31 00:01:57,080 --> 00:01:59,240 Speaker 1: is true that some part of the Moon is dark 32 00:01:59,240 --> 00:02:02,920 Speaker 1: at any particular or time, it's not always the same part. 33 00:02:03,240 --> 00:02:06,760 Speaker 1: That's because like Earth, the Moon rotates on its axis, 34 00:02:06,920 --> 00:02:09,320 Speaker 1: a meaning it has a daytime and a night time. 35 00:02:10,040 --> 00:02:11,960 Speaker 1: So if you were to set up camp on the 36 00:02:11,960 --> 00:02:15,079 Speaker 1: Moon and stay put, you would eventually see the sun 37 00:02:15,240 --> 00:02:20,880 Speaker 1: rise and fall. You'd experience both day and night. So 38 00:02:21,280 --> 00:02:23,919 Speaker 1: technically the moon does have a dark side at any 39 00:02:23,919 --> 00:02:27,120 Speaker 1: given moment, but it shifts. The dark side is the 40 00:02:27,120 --> 00:02:30,160 Speaker 1: part currently experiencing night. The side of the moon we 41 00:02:30,200 --> 00:02:33,320 Speaker 1: see is sometimes the day side, sometimes the night side, 42 00:02:33,400 --> 00:02:38,320 Speaker 1: and sometimes a bit of both. A more accurate term 43 00:02:38,400 --> 00:02:40,280 Speaker 1: to describe The side of the Moon that we always 44 00:02:40,320 --> 00:02:44,200 Speaker 1: see is the near side. The side opposite is the 45 00:02:44,200 --> 00:02:47,760 Speaker 1: far side. The near side will always be facing toward us, 46 00:02:47,880 --> 00:02:50,920 Speaker 1: and the far side will always face away. This is 47 00:02:50,960 --> 00:02:53,760 Speaker 1: true from anywhere on Earth. If you were to fly 48 00:02:53,840 --> 00:02:57,000 Speaker 1: from America to Australia or vice versa, you'd see the 49 00:02:57,000 --> 00:03:02,240 Speaker 1: same features that you're familiar with back home. But why 50 00:03:02,400 --> 00:03:04,160 Speaker 1: do we only ever see one side of the Moon 51 00:03:04,200 --> 00:03:08,960 Speaker 1: from Earth? Okay, it takes about twenty nine days for 52 00:03:09,040 --> 00:03:11,840 Speaker 1: the Moon to make one complete orbit around the Earth. 53 00:03:12,639 --> 00:03:14,960 Speaker 1: That's also how long it takes the Moon to make 54 00:03:15,000 --> 00:03:19,840 Speaker 1: one rotation on its axis. Because the Moon's rotation and 55 00:03:20,000 --> 00:03:22,880 Speaker 1: orbit take the same amount of time, we always see 56 00:03:22,919 --> 00:03:25,120 Speaker 1: the same face of the Moon no matter when we 57 00:03:25,160 --> 00:03:28,720 Speaker 1: look at it. The Moon just keeps spinning the same 58 00:03:28,800 --> 00:03:31,639 Speaker 1: side of itself toward us as it orbits around us. 59 00:03:33,760 --> 00:03:38,400 Speaker 1: This happens because of gravity. Earth's gravitational pull on the 60 00:03:38,400 --> 00:03:41,400 Speaker 1: Moon is so strong that our planets slowed the Moon's 61 00:03:41,480 --> 00:03:45,680 Speaker 1: rotation down to its current speed. Its rotational speed is 62 00:03:45,760 --> 00:03:50,400 Speaker 1: locked with the time that it takes to orbit the Earth. Interestingly, 63 00:03:50,520 --> 00:03:52,520 Speaker 1: the Moon is doing the same thing to the Earth, 64 00:03:53,000 --> 00:03:55,080 Speaker 1: just much slower because the pull of the Moon on 65 00:03:55,120 --> 00:03:58,200 Speaker 1: the Earth is much smaller, so if you've ever felt 66 00:03:58,200 --> 00:04:02,360 Speaker 1: like the days are getting longer, they are technically still. 67 00:04:02,440 --> 00:04:05,400 Speaker 1: In a few billion years, the Earth's rotation will match 68 00:04:05,480 --> 00:04:07,640 Speaker 1: the time it takes the Moon to orbit the Earth. 69 00:04:08,760 --> 00:04:10,480 Speaker 1: By that time, the Moon and the Earth will have 70 00:04:10,680 --> 00:04:12,960 Speaker 1: drifted apart from each other a little bit, which means 71 00:04:12,960 --> 00:04:15,040 Speaker 1: it'll take a little longer for the Moon to travel 72 00:04:15,040 --> 00:04:17,800 Speaker 1: around the Earth, to the tune of about forty days 73 00:04:17,880 --> 00:04:22,479 Speaker 1: or so, meaning that in the distant future, one Earth 74 00:04:22,600 --> 00:04:26,080 Speaker 1: day will equal forty of our current Earth days, or 75 00:04:26,279 --> 00:04:30,840 Speaker 1: about nine hundred and sixty hours. Once the Earth's rotation 76 00:04:31,000 --> 00:04:33,040 Speaker 1: matches the time it takes for the Moon to orbit 77 00:04:33,080 --> 00:04:35,559 Speaker 1: the Earth, the same side of the Earth will face 78 00:04:35,600 --> 00:04:42,039 Speaker 1: the Moon all the time. But okay, let's talk about 79 00:04:42,040 --> 00:04:45,680 Speaker 1: the phases of the moon. A common misconception about the 80 00:04:45,760 --> 00:04:48,640 Speaker 1: moon is that it appears as just a sliver sometimes 81 00:04:48,680 --> 00:04:51,599 Speaker 1: called a new moon, when the Earth is between the 82 00:04:51,640 --> 00:04:54,279 Speaker 1: Sun and the Moon, thus blocking the light from the 83 00:04:54,320 --> 00:04:58,640 Speaker 1: Sun and casting a shadow across the moon. But in reality, 84 00:04:59,040 --> 00:05:01,880 Speaker 1: during a new moon, the Moon is between the Sun 85 00:05:02,000 --> 00:05:05,560 Speaker 1: and the Earth. Imagine that you're in a room that's 86 00:05:05,680 --> 00:05:09,400 Speaker 1: dark except for one window that has sunlight shining into it, 87 00:05:10,360 --> 00:05:13,880 Speaker 1: and then someone walks between you and the window. You 88 00:05:13,920 --> 00:05:17,800 Speaker 1: would see the person in silhouette. They'd appear mostly shadowy, 89 00:05:18,000 --> 00:05:21,080 Speaker 1: but with a bright outline along their side facing the window. 90 00:05:21,760 --> 00:05:26,320 Speaker 1: That's exactly what a new moon is. A full moon, 91 00:05:26,360 --> 00:05:29,440 Speaker 1: in contrast, is when the Earth is between the Moon 92 00:05:29,440 --> 00:05:33,080 Speaker 1: and the sun. Going back to our example, imagine that 93 00:05:33,200 --> 00:05:36,520 Speaker 1: you're the person standing by the window. If you turn 94 00:05:36,560 --> 00:05:39,320 Speaker 1: to look into the room, anyone standing there would be 95 00:05:39,400 --> 00:05:42,479 Speaker 1: well illuminated. That's the same as us looking at a 96 00:05:42,480 --> 00:05:47,560 Speaker 1: full moon. But again, whether it's a full moon or 97 00:05:47,600 --> 00:05:50,239 Speaker 1: a new moon, you're still looking at the same side 98 00:05:50,240 --> 00:05:53,200 Speaker 1: of the moon, the near side. During a new moon, 99 00:05:53,240 --> 00:05:55,520 Speaker 1: you're looking at the near side during lunar night time, 100 00:05:55,720 --> 00:05:57,680 Speaker 1: and during a full moon you're looking at the near 101 00:05:57,760 --> 00:06:02,880 Speaker 1: sides version of noon. All of this being said, the 102 00:06:02,920 --> 00:06:05,560 Speaker 1: far side of the moon is still a little mysterious 103 00:06:06,160 --> 00:06:09,320 Speaker 1: because the Moon's bulk blocks radio signals to and from 104 00:06:09,320 --> 00:06:12,520 Speaker 1: the Earth from its far side. Engineers don't yet have 105 00:06:12,600 --> 00:06:14,799 Speaker 1: a good way for us to explore that far side. 106 00:06:15,800 --> 00:06:18,960 Speaker 1: In the future, we may see NASA and other organizations 107 00:06:19,160 --> 00:06:22,040 Speaker 1: build radio relay towers on the Moon's surface to make 108 00:06:22,080 --> 00:06:26,719 Speaker 1: exploration possible. Until then, we'll have to content ourselves with 109 00:06:26,839 --> 00:06:34,960 Speaker 1: being looney over the side that faces us. Today's episode 110 00:06:35,000 --> 00:06:37,159 Speaker 1: is based on the article what and Where is the 111 00:06:37,200 --> 00:06:39,719 Speaker 1: Dark Side of the Moon on HowStuffWorks dot com written 112 00:06:39,720 --> 00:06:43,039 Speaker 1: by Jonathan Strickland. Brain Stuff is production of iHeartRadio in 113 00:06:43,080 --> 00:06:45,600 Speaker 1: partnership with hostuffworks dot Com and is produced by Tyler 114 00:06:45,680 --> 00:06:48,880 Speaker 1: klang A. Four more podcasts my heart Radio, visit the 115 00:06:48,920 --> 00:06:52,080 Speaker 1: iHeartRadio app, Apple Podcasts, or wherever you listen to your 116 00:06:52,080 --> 00:06:52,880 Speaker 1: favorite shows.