Things You Thought You Knew – The Dark Side of the Moon

A year isn’t what you think it is… Neil deGrasse Tyson and comedian Chuck Nice explore things you thought you knew about the length of a year, the dark side of the moon, and the physics of a moving system.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Chuck Nice?

  They watch too many Warner Brothers cartoons. That's what's wrong with those people. Too many wily coyotes.

• 0:07Neil deGrasse Tyson?

  They're using the cartoon laws of physics instead of the actual laws of physics.

• 0:11Chuck Nice?

  Yeah, in that person's world, you know what else happens? Um, if you don't know that you're not standing on the edge of a cliff, you can actually stand on thin air.

• 0:21Neil deGrasse Tyson?

  Gravity only kicks in with your awareness.

• 0:23Chuck Nice?

  That's it, you know, and uh...

• 0:25Neil deGrasse Tyson?

  That's a new law of physics, right there.

• 0:29Neil deGrasse Tyson?

  Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.

• 0:42Neil deGrasse Tyson?

  Chuck.

• 0:43Chuck Nice?

  What's up, Neil?

• 0:44Neil deGrasse Tyson?

  Time for another Things You Thought You Knew.

• 0:47Chuck Nice?

  Awesome. Yes, which is pretty much everything for me. I thought I knew it, and then I found out I did not know it at all. I thought I knew that. I did not know. I did not know it.

• 1:01Neil deGrasse Tyson?

  Okay, so I got one here. You ready?

• 1:02Chuck Nice?

  Go ahead.

• 1:03Neil deGrasse Tyson?

  Uh, how long is a year?

• 1:07Chuck Nice?

  Oh, right. I, I didn't realize, uh, you thought I was that stupid that you had explained that to me. I, I said I loved explainers. I didn't realize that we were getting down to the remedial levels. Yeah. Hello, Chuck. Hi. So, yeah. What, let's, let's tell you what a year is. Now, first of all, I want you to...

• 1:28Neil deGrasse Tyson?

  So what do you, what is a year?

• 1:30Chuck Nice?

  Here's a year. Take this crayon, and I want you to draw. I want you to draw me a timeline, Chuck. A year, a year is a trip around the sun.

• 1:40Neil deGrasse Tyson?

  Okay, so how long does that take?

• 1:42Chuck Nice?

  Uh, we say that it takes 365 days, but I got a feeling that you're gonna tell me somehow that is not the case.

• 1:53Neil deGrasse Tyson?

  That is totally not the case.

• 1:54Chuck Nice?

  That is not the case. Oh, wow!

• 1:57Neil deGrasse Tyson?

  It is not the case. So, a, as a matter of social civil convenience.

• 2:04Chuck Nice?

  Okay.

• 2:04Neil deGrasse Tyson?

  Okay, uh, the year is mapped out to 365 days. All right?

• 2:10Chuck Nice?

  All right.

• 2:11Neil deGrasse Tyson?

  With 12 months, each having as few as 28 days and up to 31 days. Add all that up, you...

• 2:17Chuck Nice?

  And then every four years, we stick another day in there on that 28.

• 2:20Neil deGrasse Tyson?

  Well, that's what I'm getting at. So, that's 265 days, and we celebrate New Year's Day.

• 2:26Chuck Nice?

  Right.

• 2:28Neil deGrasse Tyson?

  Earth has not yet completed its orbit around the sun.

• 2:34Chuck Nice?

  Wait a minute. So you're saying to me that when we go January 1st, yay, all right, kiss.

• 2:42Neil deGrasse Tyson?

  When you go January 1st to January 1st.

• 2:44Chuck Nice?

  Right.

• 2:45Neil deGrasse Tyson?

  Each time we do it.

• 2:46Chuck Nice?

  Right.

• 2:47Neil deGrasse Tyson?

  Earth is six hours behind the completion of one trip around the sun.

• 2:56Chuck Nice?

  Oh crap, I did not know that. Well, first of all.

• 2:59Neil deGrasse Tyson?

  I'm telling you.

• 2:59Chuck Nice?

  First of all, that is significant in terms of amount of time.

• 3:03Neil deGrasse Tyson?

  Yes, it is. Okay, so rather than celebrate the new year in these six hour increments through, no, we just cleanly divide the year into whole days. Cause we don't want to mess with a day.

• 3:19Chuck Nice?

  Right.

• 3:19Neil deGrasse Tyson?

  You wake up in the morning, you go to sleep, the sun rises, it sets, it's day, it's night. We want to keep that intact. So we ignore the six hours.

• 3:28Chuck Nice?

  Okay.

• 3:30Neil deGrasse Tyson?

  All right. So now, how long you gonna ignore the six hours?

• 3:33Chuck Nice?

  Well, I'm gonna say not very long.

• 3:36Neil deGrasse Tyson?

  Okay, so if you, if you ignore it for four years.

• 3:41Chuck Nice?

  That's a day.

• 3:42Neil deGrasse Tyson?

  Then how many hours have you ignored?

• 3:43Chuck Nice?

  Twenty-four, six times four.

• 3:45Neil deGrasse Tyson?

  Bada bing. So you then throw a day back into the calendar.

• 3:51Chuck Nice?

  That makes sense. Every six hours, six hours, four years, that's a day. Throw the day back in. All right, people, let's keep it moving.

• 3:59Neil deGrasse Tyson?

  And you're back in line. And we give that day to the very needy February.

• 4:02Chuck Nice?

  Right.

• 4:03Neil deGrasse Tyson?

  Um, of course, Black History Month.

• 4:04Chuck Nice?

  Yes, exactly. Of course they would do that. You know that. Just like, not only are we missing a day. It's the shortest month of the year. And, uh, oh, by the way, black people, here you go.

• 4:16Neil deGrasse Tyson?

  By the way, it's the shortest month, even when you give it an extra day.

• 4:19Chuck Nice?

  Even when you give it an extra day, we still don't come, we still come up short. That's amazing.

• 4:24Neil deGrasse Tyson?

  All right.

• 4:25Chuck Nice?

  So.

• 4:26Neil deGrasse Tyson?

  So now, and now everything's sort of even Steven, okay?

• 4:29Chuck Nice?

  Right.

• 4:30Neil deGrasse Tyson?

  All right. So what we've talked, I think we've talked about before, the fact that that over corrects.

• 4:39Neil deGrasse Tyson?

  Did I, did I ever mention that to you?

• 4:40Chuck Nice?

  Okay, now, I, I believe we did, but we were talking about it in a different.

• 4:46Neil deGrasse Tyson?

  It might have been a different context.

• 4:47Chuck Nice?

  Calendar, calendars. There was like a Julian calendar.

• 4:50Neil deGrasse Tyson?

  Exactly.

• 4:50Chuck Nice?

  We talked about this two years ago. I'm trying to think of it.

• 4:53Neil deGrasse Tyson?

  I'm gonna reach down over the back, because it's in, it's relates to the year.

• 4:56Chuck Nice?

  Yeah, okay.

• 4:57Neil deGrasse Tyson?

  I told you six hours, but it's not six hours.

• 5:00Chuck Nice?

  Okay, of course. I mean, that's right, because that only makes sense. Okay, it's a trip around the sun, 365 days, except it's not. Um, and it's six hours, except it's not.

• 5:12Neil deGrasse Tyson?

  Okay, it's a little less than six hours. So, Chuck, since it's a little less than six hours.

• 5:19Chuck Nice?

  Mm-hmm.

• 5:20Neil deGrasse Tyson?

  If you add up four of those, you don't quite have a full day, do you?

• 5:25Chuck Nice?

  No, yeah, exactly. You're a little short.

• 5:28Neil deGrasse Tyson?

  Yet we put in a full day.

• 5:29Chuck Nice?

  Right.

• 5:30Neil deGrasse Tyson?

  So it turns out, over a century, you've accumulated an extra day that shouldn't be there.

• 5:38Chuck Nice?

  Okay.

• 5:40Neil deGrasse Tyson?

  So, every century, when it would have been a leap day, you take it out.

• 5:47Chuck Nice?

  So, okay, gotcha, because we're, right, we've accumulated that day. We don't need to have the leap year that time. So we just let it go, the day self-corrects, because the accounting, the ledger is now balanced.

• 6:05Neil deGrasse Tyson?

  It, except.

• 6:06Chuck Nice?

  Except, oh god.

• 6:07Neil deGrasse Tyson?

  Quite.

• 6:08Chuck Nice?

  Oh, god. God, what?

• 6:12Neil deGrasse Tyson?

  Okay, okay, so, it turns out that over-corrects it by just a little bit.

• 6:21Chuck Nice?

  Of, of course it would.

• 6:23Neil deGrasse Tyson?

  Okay.

• 6:23Chuck Nice?

  Right.

• 6:24Neil deGrasse Tyson?

  Over-corrects it. So, over 400 years.

• 6:33Neil deGrasse Tyson?

  There's a day that should be in there that isn't.

• 6:38Chuck Nice?

  Okay.

• 6:39Neil deGrasse Tyson?

  Okay, so every 400 years.

• 6:43Chuck Nice?

  Right.

• 6:43Neil deGrasse Tyson?

  Which counts as a hundred year increment.

• 6:46Chuck Nice?

  Right, that's true.

• 6:47Neil deGrasse Tyson?

  Where you would have taken out the leap day.

• 6:49Chuck Nice?

  Right.

• 6:49Neil deGrasse Tyson?

  Every 400 years, you put the leap day back in.

• 6:52Chuck Nice?

  You put it back in, because you wouldn't have taken it out, because it's the correction for the times that already was accumulated. You wouldn't have, you would have just let things be. But now, over 400 years, because it wasn't quite what it is, well, just a little bit, it took 400 years, now it's just like, hey, now, you know what we're gonna do? Because we actually did accumulate over all this time, so now, we're gonna shove a day back in here, and finally.

• 7:20Neil deGrasse Tyson?

  Every 400, and you know something? The year 2000 was just such a year. So, most people who said, well, year 2000 is divisible by 4, it's a leap year.

• 7:33Chuck Nice?

  Right.

• 7:34Neil deGrasse Tyson?

  Had no clue how rare a leap year that is.

• 7:38Chuck Nice?

  Right, that was the leap year that wasn't.

• 7:40Neil deGrasse Tyson?

  Yeah, correct, there was no leap day in the year 1900, or in the year 1700. So, all those century years had to accumulate a 400-year interval. We're up to the year 2000, it's got a leap day, and people thought that was a normal leap day, but it wasn't.

• 7:57Chuck Nice?

  But it wasn't, wow.

• 7:59Neil deGrasse Tyson?

  Yep.

• 8:00Chuck Nice?

  That's actually a, wow, look at that, that's, this.

• 8:03Neil deGrasse Tyson?

  Okay, it's all because we're not correcting by the precise amount.

• 8:07Chuck Nice?

  Right.

• 8:07Neil deGrasse Tyson?

  We're correcting by whole days. Earth's orbit around the sun doesn't care about how long it takes Earth to rotate on its axis.

• 8:14Chuck Nice?

  Oh, I see.

• 8:14Neil deGrasse Tyson?

  But we do, so we are shoehorning in our days.

• 8:18Chuck Nice?

  Right.

• 8:19Neil deGrasse Tyson?

  With respect to how long it takes Earth to go around the sun.

• 8:22Chuck Nice?

  Excellent.

• 8:23Neil deGrasse Tyson?

  Okay, so now, but wait.

• 8:26Chuck Nice?

  Oh. Oh.

• 8:29Neil deGrasse Tyson?

  We, okay, so that year is the time it takes.

• 8:37Neil deGrasse Tyson?

  The sun's and earth's relationship to repeat in such a way that the seasons stay attached to the months of the year we've given them to.

• 8:49Chuck Nice?

  Uh huh.

• 8:50Neil deGrasse Tyson?

  So our year is based on the seasonal calendar because we're historically agrarian.

• 8:55Chuck Nice?

  Agrarian, yeah. Planting, sowing, reaping, all that crap.

• 8:59Neil deGrasse Tyson?

  It makes sense, okay? It turns out that the seasonal calendar

• 9:04Chuck Nice?

  Okay.

• 9:06Neil deGrasse Tyson?

  is slightly different from the time it takes earth to return to the same spot in its orbit.

• 9:14Chuck Nice?

  Ah.

• 9:15Neil deGrasse Tyson?

  We simply don't use that calendar. And that's called a sidereal year, where we match up with the stars that surround the sun. But our seasons don't match up with the stars. And the stars migrate through the year. The sky you see in the springtime in March will shift

• 9:35Neil deGrasse Tyson?

  against the calendar, because that's not the year that we're based on. Okay, so whatever year you're based on that repeats every year, other accountings will then shift relative to it. And so when we return to our spot in space relative to all the stars, that's a different length of time than the time for us to repeat the seasons.

• 9:59Chuck Nice?

  Right.

• 9:59Neil deGrasse Tyson?

  And so, so, so we have a seasonal year, that's the year we know and love. Then it's called the sidereal year. Sidereal just simply means star.

• 10:07Chuck Nice?

  Right.

• 10:08Neil deGrasse Tyson?

  Okay.

• 10:08Chuck Nice?

  And that's right. That's the year where you look up and you have to find a point and we've got to return to that point.

• 10:14Neil deGrasse Tyson?

  To that point. And if we did that, then the seasons would drift. The stars would stay where they are.

• 10:20Chuck Nice?

  Right, right.

• 10:21Neil deGrasse Tyson?

  Okay.

• 10:22Chuck Nice?

  Right, but we'd be getting a little, you know, you know, but we don't have to worry about that anymore because we have climate change. So we have solved that problem. Solved the calendar problem. We solved the calendar problem.

• 10:33Neil deGrasse Tyson?

  There's no winters.

• 10:34Chuck Nice?

  There's no nothing, baby.

• 10:38Neil deGrasse Tyson?

  Okay, but wait, one land, there's another kind of year.

• 10:41Chuck Nice?

  Okay.

• 10:42Neil deGrasse Tyson?

  Okay. Earth is an ellipse in its orbit.

• 10:45Chuck Nice?

  Right.

• 10:46Neil deGrasse Tyson?

  Okay. Okay. So, that means sometimes it's closer to the sun and sometimes it's farthest.

• 10:52Chuck Nice?

  Right.

• 10:52Neil deGrasse Tyson?

  Right? We're closest to the sun in July, farthest in, in January, early January.

• 10:59Chuck Nice?

  Right.

• 10:59Neil deGrasse Tyson?

  So, that ellipse precesses around the sun.

• 11:06Neil deGrasse Tyson?

  So, in other words, if you looks, if you step back and look at the ellipse orbit around the sun, and watch it like for thousands of years, that entire ellipse will turn around the sun.

• 11:20Chuck Nice?

  Gotcha.

• 11:20Neil deGrasse Tyson?

  Okay? It's called precession. It's a, there are various kinds of precession, that's one of them. So, if you timed, the time between our closest point to the sun, and our closest point to the sun again, that's a kind of a year, isn't it?

• 11:36Chuck Nice?

  Yeah, it would be, yeah.

• 11:37Neil deGrasse Tyson?

  That would be a year within our orbit. That's a different length year from the sidereal year, different length year from our, from our seasonal.

• 11:45Chuck Nice?

  Seasonal year. Wow. I, now, here's the thing.

• 11:50Neil deGrasse Tyson?

  Yeah.

• 11:50Chuck Nice?

  How, how much older am I, uh, based on all these years?

• 11:58Neil deGrasse Tyson?

  It's a very small difference between them.

• 12:00Chuck Nice?

  Oh, okay.

• 12:01Neil deGrasse Tyson?

  Yeah, yeah, it's not, right, but, no.

• 12:03Chuck Nice?

  I'm just seeing if I can cheat the system.

• 12:07Neil deGrasse Tyson?

  Yeah, just consider that, um, that what we chose as a year is in a sense arbitrary. Not that the length of the year is arbitrary, but we had a choice of three.

• 12:17Chuck Nice?

  Right.

• 12:18Neil deGrasse Tyson?

  And, and we don't care about whether the stars in March stay the stars in March. We care that March always has spring.

• 12:24Chuck Nice?

  That's it.

• 12:24Neil deGrasse Tyson?

  At least in the northern hemisphere, right?

• 12:26Chuck Nice?

  Exact.

• 12:27Neil deGrasse Tyson?

  There you go, that's, that's the years in a nutshell.

• 12:29Chuck Nice?

  That was good stuff, I'm gonna say. I, you know, when you started off with, with, you know, what is a year? I was kinda like, you lost it, bro. You finally lost it. You, he's finally gone. But you pulled it out, I gotta tell you, you pulled it out. This was a good one. This was a good one.

• 12:47Neil deGrasse Tyson?

  That's kind of the whole point of these things you brought to me.

• 12:50Chuck Nice?

  That's true, that's true.

• 13:04Neil deGrasse Tyson?

  Chuck got another one.

• 13:05Chuck Nice?

  Okay, and another one.

• 13:07Neil deGrasse Tyson?

  Okay.

• 13:08Chuck Nice?

  And another one.

• 13:09Neil deGrasse Tyson?

  It's in our culture.

• 13:10Chuck Nice?

  Okay.

• 13:11Neil deGrasse Tyson?

  There's no escaping it.

• 13:13Chuck Nice?

  Right.

• 13:13Neil deGrasse Tyson?

  Some percentage of people who walk this earth, when asked, would be sure that there's such a thing as "The Dark Side of the Moon."

• 13:23Chuck Nice?

  Yeah, that's where the Transformers hide out.

• 13:27Neil deGrasse Tyson?

  I thought it was just the other side of the moon.

• 13:30Neil deGrasse Tyson?

  So, so "The Dark Side of the Moon", I think, hit a peak in 1973. You know what happened then?

• 13:40Chuck Nice?

  Uh, did Pink Floyd put out an album?

• 13:42Neil deGrasse Tyson?

  Pink Floyd put out an album.

• 13:43Chuck Nice?

  Because that, that would do it.

• 13:46Neil deGrasse Tyson?

  And, you know, the album did really well.

• 13:49Chuck Nice?

  Yeah.

• 13:49Neil deGrasse Tyson?

  That's the problem. If, if people hated the album, my job would have been way easier because no one would have been brainwashed by it.

• 13:56Chuck Nice?

  Exactly.

• 13:57Neil deGrasse Tyson?

  So it was the title of the album called "The Dark Side of the Moon." And so, I've been spending 50 years, this is the 50th year anniversary, 2023 is the 50th year anniversary of the release of that album. I've spent every one of those 50 years trying to undo the damage caused by the title of that album.

• 14:14Chuck Nice?

  Wow. See, now, what you should have done is just, you know, you should have took Pink Floyd out the same way you took out Pluto.

• 14:24Chuck Nice?

  Would not have to worry about this.

• 14:28Neil deGrasse Tyson?

  Yeah, get authoritative legislation.

• 14:33Neil deGrasse Tyson?

  "The Dark Side of the Moon" is now "Dwarf Side of the Moon." So, now, if you, if you listen to the title track, like, with headphones, the very last sentence, the very last two sentences, you know what they are?

• 14:46Chuck Nice?

  I do not.

• 14:47Neil deGrasse Tyson?

  Okay, but you gotta listen because there's a lot of fadey kind of music in, in all of those tracks. So you listen, and it's, it says at the end, "There is no dark side of the moon."

• 14:58Chuck Nice?

  Are you serious?

• 14:59Neil deGrasse Tyson?

  Yes.

• 15:00Chuck Nice?

  Wait, wait, wait. So I said, "Okay, that was all. People just listened to the song."

• 15:04Neil deGrasse Tyson?

  However, there's a sentence that follows it.

• 15:07Chuck Nice?

  Well, of course, there has to be.

• 15:10Neil deGrasse Tyson?

  There's a three-word sentence that follows it, right? So it says, "There is no dark side of the moon. It's all dark."

• 15:18Chuck Nice?

  Oh, that's a little more philosophical.

• 15:22Neil deGrasse Tyson?

  That's a little more philosophical, yeah.

• 15:24Chuck Nice?

  Yeah.

• 15:25Neil deGrasse Tyson?

  But then I said, "I can't get on a case too much here," because it's just being poetic.

• 15:29Chuck Nice?

  Yeah, well.

• 15:30Neil deGrasse Tyson?

  And, but anyhow, there are people who still think that the other side of the moon never sees sunlight.

• 15:38Chuck Nice?

  True.

• 15:38Neil deGrasse Tyson?

  Which is interesting for anybody to think that, because you've never seen the far side, that side of the moon. So why would you even conclude that? You have no data, okay?

• 15:47Chuck Nice?

  Right.

• 15:48Neil deGrasse Tyson?

  The moon does always show the same face to Earth. We went over that in a previous session.

• 15:52Chuck Nice?

  Title locking.

• 15:54Neil deGrasse Tyson?

  Title locking, that's right.

• 15:55Chuck Nice?

  Right.

• 15:55Neil deGrasse Tyson?

  So the other side of the moon is, gets as much sunlight as the near side, so there's a far side and a near side.

• 16:04Chuck Nice?

  Near side, right.

• 16:04Neil deGrasse Tyson?

  And a day on the moon lasts 30 days, 30 Earth days. So there's like 15 days of sunlight and 15 days of darkness.

• 16:13Chuck Nice?

  Gotcha.

• 16:14Neil deGrasse Tyson?

  So, yeah, so moon has days, just as we do. But, so, you see, had you thought about it, Chuck? When you see a half moon in the sky?

• 16:23Chuck Nice?

  Right.

• 16:24Neil deGrasse Tyson?

  Wouldn't you think that, like, the half you don't see on the other side is also getting sunlight?

• 16:30Chuck Nice?

  Right, well, I mean, isn't that how shadows work?

• 16:35Neil deGrasse Tyson?

  Shadows and round things.

• 16:36Chuck Nice?

  Shadows and round things kind of work that way, you know?

• 16:41Neil deGrasse Tyson?

  Yeah, so that should, that should have, people should have been tipped off by that.

• 16:45Chuck Nice?

  Right.

• 16:46Neil deGrasse Tyson?

  Uh, so, so here's the thing. Uh, when the Indians, uh, landed their, had their first successful landing on the moon, becoming the fourth country to do so, from Soviet Union back in the day.

• 17:03Chuck Nice?

  Right.

• 17:04Neil deGrasse Tyson?

  And the United States.

• 17:05Chuck Nice?

  Right.

• 17:06Neil deGrasse Tyson?

  By the way, Soviet Union got there first. Soviet Union beat us at everything. Until we put humans on the moon, then we said, we win.

• 17:12Chuck Nice?

  So, hey, man, that's how you got it. That's how you win. You change the rules.

• 17:17Neil deGrasse Tyson?

  You change the goalpost?

• 17:19Chuck Nice?

  Change, move the goalposts and change the rules, man.

• 17:22Neil deGrasse Tyson?

  So, yeah, they beat us at the first, they had the first satellite, the first non-human animal, the first human.

• 17:28Chuck Nice?

  And then we were just, and then we were just like, none of that counts. Okay, because we put the first dude.

• 17:39Neil deGrasse Tyson?

  Russia even had the first black person who was a Cuban, uh, he was a Cuban.

• 17:43Chuck Nice?

  Okay, dark-skinned Cuban, right.

• 17:45Neil deGrasse Tyson?

  So anyhow, so we, so they became the fourth country to do this. And but what's more significant than that, because that that would just be, okay, welcome to the club. All right, they landed near the moon's south pole. And the south pole, I think we talked about in a previous explainer, uh, you have the bases of craters. The sun never gets high enough in the sky.

• 18:07Chuck Nice?

  Right.

• 18:08Neil deGrasse Tyson?

  Because near the poles, the sun is, stays low.

• 18:10Chuck Nice?

  Right.

• 18:10Neil deGrasse Tyson?

  Stays so low that sunlight never reaches the bottom of the crater. And so it's, it's literally where the sun don't shine.

• 18:18Chuck Nice?

  Yeah.

• 18:18Neil deGrasse Tyson?

  Okay, there are literal dark places on the moon.

• 18:23Chuck Nice?

  Right.

• 18:23Neil deGrasse Tyson?

  Okay, all right. So, here's the thing. The Indian spacecraft landed not in the bottom of a crater, because that's, that it's, it has solar panels and it needs energy. So it landed outside the crater, but in darkness. And so why would they do that? Well, here's what they did. They landed on the last day of nighttime.

• 18:52Chuck Nice?

  Ah, the 30th day.

• 18:54Neil deGrasse Tyson?

  Okay, on the last day of nighttime. So that the next day, the sun rose, and how much daylight do they get?

• 19:03Chuck Nice?

  They get 15 days now.

• 19:04Neil deGrasse Tyson?

  They get 15 days, so it's a, it's a two-week mission.

• 19:07Chuck Nice?

  No, that was so smart.

• 19:10Neil deGrasse Tyson?

  Yes.

• 19:12Chuck Nice?

  Ah, that's really cool.

• 19:14Neil deGrasse Tyson?

  Yeah.

• 19:14Chuck Nice?

  So now they have two weeks to go look for their ice or whatever.

• 19:17Neil deGrasse Tyson?

  Yeah, yeah, the water has to be frozen, of course.

• 19:19Chuck Nice?

  Frozen water, yeah.

• 19:21Neil deGrasse Tyson?

  Yeah, and so, uh, yeah, it's smart people are people who figure this stuff out. And as a matter of fact, it is rocket science, right? Because they have to leave Earth.

• 19:32Chuck Nice?

  Right.

• 19:32Neil deGrasse Tyson?

  So that they landed there at that time.

• 19:35Chuck Nice?

  That's right, that's right.

• 19:36Neil deGrasse Tyson?

  Okay. So, so, oh, so my point is, there were some Indian headlines that said, um, Chandrayaan III, which is the name of that mission, landed on, in, on the dark side of the moon.

• 19:50Chuck Nice?

  Oh.

• 19:51Neil deGrasse Tyson?

  Yeah, see, so they got, they got caught up in that.

• 19:54Chuck Nice?

  Yeah, but that wasn't the Indian space program saying that. It was the journalists who don't understand that there is no dark side.

• 20:03Neil deGrasse Tyson?

  Apparently, Pink Floyd's album had worldwide influence that I didn't know.

• 20:06Chuck Nice?

  Yeah, well, the album sales could have told you that.

• 20:11Neil deGrasse Tyson?

  So, I, I think they might have seen it landed in the dark. And then, moon, and when dark becomes dark side.

• 20:20Chuck Nice?

  Dark side of moon, wow.

• 20:21Neil deGrasse Tyson?

  Yeah, yeah. And so, uh, so you might ask, well, how cold is it where the sun don't shine?

• 20:28Chuck Nice?

  Oh, how cold is it where the sun don't shine?

• 20:31Neil deGrasse Tyson?

  Hundreds of degrees below zero.

• 20:33Chuck Nice?

  And that makes things difficult, doesn't it?

• 20:35Neil deGrasse Tyson?

  And so, so this water, which would have arrived by comets, you know, moon's been hit by stuff.

• 20:41Chuck Nice?

  Yeah.

• 20:41Neil deGrasse Tyson?

  In case you didn't notice, the, the, the acne.

• 20:45Chuck Nice?

  That's why the man, yeah, that's why the man on the moon's face looks like a pepperoni pizza. What a terrible saying, the guy looks like he's, like has some serious hormonal problems going on.

• 20:56Neil deGrasse Tyson?

  Some teenage acne issues.

• 20:57Chuck Nice?

  The man on the moon is not getting a date to the prom, that's all I'm saying. It's gonna be tough, really, it's rough, it's rough, need a little Accutane.

• 21:05Neil deGrasse Tyson?

  So, because there's no atmosphere to smooth out the hot places and the cold places.

• 21:09Chuck Nice?

  Uh huh.

• 21:10Neil deGrasse Tyson?

  Because what happens is, in our air, our air sort of captures the heat once the sun heats the ground, and it moves that around, right? That doesn't happen on the moon. So, uh, where the sun is shining is 200 degrees above zero. You can sit out with a cup of water and boil it.

• 21:27Chuck Nice?

  Right.

• 21:28Neil deGrasse Tyson?

  And in the, in the, where the sun doesn't shine, it's hundreds of degrees below zero. So really, if you're there, the side of you facing the sun is gonna be hot and the side of you not facing the sun will rapidly cool off. So ideally, you should go on a rotisserie.

• 21:45Chuck Nice?

  Right. My Boston chicken.

• 21:51Neil deGrasse Tyson?

  So Bobby said, there's a reason for space suits to be reflective typically.

• 21:54Chuck Nice?

  Right, right.

• 21:55Neil deGrasse Tyson?

  Because you wanna be in full control of what's going on. So of course, they had, you know, those big packs that were on the astronauts' backs.

• 22:02Chuck Nice?

  Right.

• 22:03Neil deGrasse Tyson?

  Half of that, I don't have half, but a big part of it was their, their, um, the cooling system that keeps them at the right temperature so they don't bake or freeze.

• 22:13Chuck Nice?

  Nice.

• 22:14Neil deGrasse Tyson?

  And one other thing before we end this, uh, because there is no atmosphere, that means there's no skylight. There's no blue sky in the daytime. The daytime sky is just dark.

• 22:26Chuck Nice?

  Right.

• 22:26Neil deGrasse Tyson?

  Alright. So the only source of light are direct sightlines from the sun.

• 22:36Chuck Nice?

  Wow.

• 22:36Neil deGrasse Tyson?

  So if you're standing there, Chuck, and you, part of you is in shadow, unless some light is reflecting off the lunar terrain, it is pitch dark.

• 22:49Chuck Nice?

  Look at that.

• 22:49Neil deGrasse Tyson?

  In the shadows of rocks and in your shadow, pitch dark.

• 22:52Chuck Nice?

  Wow.

• 22:53Neil deGrasse Tyson?

  In broad daylight. So that makes for fascinating contrasty photos when this happens. Yes, you can get a reflection off the lunar module.

• 23:02Chuck Nice?

  Right.

• 23:03Neil deGrasse Tyson?

  Okay, but the general ambient light we take for granted when you walk around in the daytime is not there on the moon.

• 23:09Chuck Nice?

  Look at that.

• 23:10Neil deGrasse Tyson?

  Yeah.

• 23:11Chuck Nice?

  That's cool.

• 23:12Neil deGrasse Tyson?

  So, so Chuck, there is no dark side of the moon. That's all I gotta tell you.

• 23:15Chuck Nice?

  Well, there you go. Pink Floyd, you're a bunch of dummies.

• 23:22Neil deGrasse Tyson?

  So Chuck, I was actually at a party one day when I met Roger Waters.

• 23:26Chuck Nice?

  Very cool.

• 23:27Neil deGrasse Tyson?

  Yeah.

• 23:27Chuck Nice?

  And you told him that there was no dark side?

• 23:30Neil deGrasse Tyson?

  Chuck, I had to. I couldn't remain silent.

• 23:32Chuck Nice?

  And what was his response?

• 23:34Neil deGrasse Tyson?

  He was not sympathetic.

• 23:36Chuck Nice?

  Oh, that makes sense. He's like, "Bro, I'm getting paid off this."

• 23:39Neil deGrasse Tyson?

  He got gravy trained.

• 23:41Chuck Nice?

  Yeah, "I got a nice little racket going here with this dark side of the moon thing, and you are messing it up. I'm gonna need you to silence. I'm gonna..."

• 23:49Neil deGrasse Tyson?

  Don't make me take out a gag order on you, Neil.

• 23:53Neil deGrasse Tyson?

  But anyhow, you know, the job of the educator never ends. I think that's what's going on.

• 23:57Chuck Nice?

  Very cool.

• 23:58Neil deGrasse Tyson?

  As long as there are forces of untruths that pervade the world.

• 24:03Chuck Nice?

  Okay, look how poetic you are. I was about to say, as long as there are ignorant dumbasses.

• 24:11Chuck Nice?

  The job of the educator shall not be finished.

• 24:17Neil deGrasse Tyson?

  All right, that's all I got for you on the dark side of the movie.

• 24:30Speaker 02

  Hey, I'm Roy Hill Percival and I support StarTalk on Patreon, bringing the universe down to earth. This is StarTalk with Neil deGrasse Tyson.

• 24:45Neil deGrasse Tyson?

  Chuck, got another one for you?

• 24:46Chuck Nice?

  Ready.

• 24:47Neil deGrasse Tyson?

  There's no limit to these. You must know that by now.

• 24:49Chuck Nice?

  I'm good for that. I'm glad there's no limit. I like them.

• 24:52Neil deGrasse Tyson?

  Okay, so this one is, we've heard this, people have talked about it and thought about it. What happens when you jump in an airplane?

• 25:02Chuck Nice?

  Well, hopefully you're going somewhere. I don't know. What do you mean, what happens when you jump in an airplane?

• 25:07Neil deGrasse Tyson?

  Airplane flying.

• 25:08Chuck Nice?

  Oh, you mean what happens when you literally jump in the air?

• 25:12Neil deGrasse Tyson?

  Yeah.

• 25:12Chuck Nice?

  I thought you'd be like, yeah, jump in an airplane, I'm going here, you know?

• 25:15Neil deGrasse Tyson?

  Oh, jump onto an airplane. No, you're in the airplane, in the aisle, and then you jump.

• 25:22Chuck Nice?

  Okay, yeah, you go up and down.

• 25:24Neil deGrasse Tyson?

  Some people think that the airplane's going 500 miles an hour.

• 25:30Chuck Nice?

  Right.

• 25:31Neil deGrasse Tyson?

  If you jump, you end up pinned against the back wall.

• 25:35Chuck Nice?

  They watch too many Warner Brothers cartoons.

• 25:40Chuck Nice?

  That's what's wrong with those people. Too many wily coyotes.

• 25:43Neil deGrasse Tyson?

  They're using the cartoon laws of physics instead of the actual laws of physics.

• 25:46Chuck Nice?

  In that person's world, you know what else happens? If you don't know that you're not standing on the edge of a cliff, you can actually stand on thin air.

• 25:56Neil deGrasse Tyson?

  Gravity only kicks in with your awareness.

• 25:59Chuck Nice?

  That's it, you know, and...

• 26:01Neil deGrasse Tyson?

  That's a new law of physics right there. Plus, if you're hitting the head with a frying pan, your face takes the shape of the frying pan.

• 26:07Chuck Nice?

  Of the frying pan, that's right. You just become two big eyes with a round face. That's right. Yes.

• 26:13Neil deGrasse Tyson?

  Cartoon laws of physics.

• 26:14Chuck Nice?

  Cartoon laws of physics.

• 26:15Neil deGrasse Tyson?

  So what I, my answer here might be obvious, but I know there are people out there who wondered whether... The plane would just sort of escape from under your feet for how fast it's moving.

• 26:26Chuck Nice?

  Right.

• 26:27Neil deGrasse Tyson?

  So this is a very basic sort of first week of physics that you learn this and you see demonstrations of it. But I will now tell you.

• 26:35Chuck Nice?

  Okay.

• 26:37Neil deGrasse Tyson?

  When the plane takes off and it is cruising at some constant speed.

• 26:44Chuck Nice?

  Mm hmm.

• 26:45Neil deGrasse Tyson?

  Pick any speed.

• 26:46Chuck Nice?

  Five hundred and sixty three miles per hour.

• 26:47Neil deGrasse Tyson?

  Fine, if it's constant, the plane is moving five hundred and sixty three miles an hour. And so are you.

• 26:55Chuck Nice?

  Right.

• 26:55Neil deGrasse Tyson?

  And so is the air inside the plane.

• 27:00Chuck Nice?

  This is cool.

• 27:01Neil deGrasse Tyson?

  So is the fly that happened to fly into the plane of after they closed the before they closed the door.

• 27:07Chuck Nice?

  Right.

• 27:08Neil deGrasse Tyson?

  You, the air, the fly are moving five hundred and sixty three miles per hour. If you're all moving at the same speed together.

• 27:18Neil deGrasse Tyson?

  Then you don't know how fast you're moving.

• 27:20Chuck Nice?

  Yeah, you're not moving at all.

• 27:21Neil deGrasse Tyson?

  You're not basically in the moving reference frame of the plane, you're not moving at all.

• 27:27Chuck Nice?

  Yeah.

• 27:28Neil deGrasse Tyson?

  So if you jump up, you will land right back where you started.

• 27:32Chuck Nice?

  Right.

• 27:33Neil deGrasse Tyson?

  It's that simple. All right, so now, so let's let's unpack this. Let me get a round number. Let's say you're going six hundred miles an hour.

• 27:41Chuck Nice?

  Okay.

• 27:41Neil deGrasse Tyson?

  Six hundred miles an hour is ten miles per minute.

• 27:45Chuck Nice?

  Right.

• 27:46Neil deGrasse Tyson?

  That's a mile every six seconds. Okay, and in New York City, there's twenty blocks per mile. So that's by like three blocks per second. Okay.

• 27:57Chuck Nice?

  Oh, man, can can we find that transportation system?

• 28:00Neil deGrasse Tyson?

  Three blocks per second.

• 28:01Chuck Nice?

  So I can get around Manhattan the way I'd like to, man, that'd be fantastic.

• 28:05Neil deGrasse Tyson?

  That would be a flying car, maybe would do that. Okay, so now watch. So if you jump up. And in the plane, it's going 600 miles an hour, you stay airborne for one second. Right. And then you land where you started. Right. Also move forward three blocks. So if someone is outside of the plane and watched you, you would jump up and you would follow this arc. Right. A parabolic arc through the air, through space, through my whole, my coordinate system. You, in my reference frame, because I'm outside of the plane, I see you jump and land.

• 28:49Neil deGrasse Tyson?

  And there's a beautiful parabolic arc that you took. Right. You also get a gold medal when you land. A long jump.

• 28:59Neil deGrasse Tyson?

  So, so another way to do this is, and we do this in physics class. If you have a train, like a model train in the front of the room, physics demos, this is a great physics demo. And the, the smokestack of the train has a little spring. You can put a ping pong ball in it, or, or no, not a ping pong, like a, just a tiny ball. Right. So, as the train is going, a tiny ball like a. A Styrofoam ball. No, no, it has to be a little heavier than that, like a, you know, a rubber ball or something. Okay? Uh, or let's take a golf ball, which is dense enough for this to work. So, there it is. As the train is moving, the spring can pop the golf ball straight up.

• 29:44Neil deGrasse Tyson?

  Okay. And then where does the golf ball land? Does the train leave it behind? No! No. Because the golf ball had the same forward motion as the train did. All the train did was give it upwards motion, like you jumping in the airplane. Right. Then it fell back down, so it'll shoot it up and it'll fall back down and land exactly back in the nozzle.

• 30:07Neil deGrasse Tyson?

  You will see it take that arc and land where it had taken off. And that is the train and golf ball version of you jumping inside of an airplane. As far as you're concerned, you're landing in the same spot. But as far as I'm concerned, you're not.

• 30:22Chuck Nice?

  Right.

• 30:23Neil deGrasse Tyson?

  You're three blocks farther down the, down the road.

• 30:25Chuck Nice?

  Cool.

• 30:26Neil deGrasse Tyson?

  So, so it's, it's, it has to do with your reference frame. And it's a remarkable thing. If, if the vessel is big enough, so you don't feel jiggles, you don't know how fast the thing is going. We're on Earth. Earth is going eight, 18 miles per second around the sun.

• 30:47Chuck Nice?

  Oh.

• 30:47Neil deGrasse Tyson?

  Okay. Now, if you want to land in a different place, do that while the plane is accelerating.

• 30:56Chuck Nice?

  Right.

• 30:57Neil deGrasse Tyson?

  Okay, now the, the flight attendants won't let you do this, but.

• 31:00Chuck Nice?

  Yeah.

• 31:01Neil deGrasse Tyson?

  Right when the plane touches down.

• 31:02Chuck Nice?

  Killjoys they are. Ah, ah, ah, just trying to do a physics experiment here. Wait a minute, I gotta sit down and pass in my seatbelt and put my, and why is, what is it with the seat in the upright position? The seat only goes back two and a half inches. Please, please put your seat up, sir, sir. Please put your seat up. I'm saying, what, what? Oh, sorry, let me put my seat up. Okay, there you go.

• 31:26Neil deGrasse Tyson?

  Yeah, because now you'll survive the crash before you wouldn't have.

• 31:29Chuck Nice?

  Oh, thank you for saving my life with this two and a half inch differential. Oh.

• 31:36Neil deGrasse Tyson?

  So, actually, I think I know why they do that.

• 31:39Chuck Nice?

  Really, why?

• 31:40Neil deGrasse Tyson?

  Yeah, you want to know why?

• 31:41Chuck Nice?

  I would like to know, to be honest.

• 31:43Neil deGrasse Tyson?

  That when all the seats are aligned, if you're climbing to get out in a wreckage, then you don't have to navigate differently oriented seats.

• 31:53Chuck Nice?

  That makes sense.

• 31:54Neil deGrasse Tyson?

  Yeah.

• 31:55Chuck Nice?

  That makes sense.

• 31:56Neil deGrasse Tyson?

  I'm pretty sure that's how that, how that rolls.

• 31:57Chuck Nice?

  All right.

• 31:58Neil deGrasse Tyson?

  So. If you magically got permission to do a physics experiment the moment the wheels touched, okay, what happens the moment the wheels touch on a runway? They put the engines into reverse thrust, okay? And so now the engine exhaust reverses and is pointing forward instead of backwards. And if they, if necessary, they'll also apply their brakes. So they might be landing at 200 miles an hour and it's ultimately zero. Okay, okay. If you jump while that's happening, you will not land in the same spot.

• 32:37Neil deGrasse Tyson?

  Because when you jumped, the plane was going 200 miles an hour. But when you landed, the plane was going 180 miles an hour. You jump again, and so you have a faster speed going forward than the plane does because the plane is slowing down. So you could just jump up and down while the plane is on the runway and ultimately end up in the cockpit.

• 32:57Chuck Nice?

  Nice.

• 32:58Neil deGrasse Tyson?

  Well, just by jumping straight up and down.

• 33:00Chuck Nice?

  Yeah, but the door will be locked because, you know, security reasons.

• 33:03Neil deGrasse Tyson?

  Yeah, they'll shoot you if you.

• 33:05Chuck Nice?

  Yeah, I was gonna say, you won't quite make it.

• 33:08Neil deGrasse Tyson?

  So consider that's why they're animate about your seatbelt on takeoff and landing. Right. But not when you're cruising.

• 33:20Chuck Nice?

  Yeah.

• 33:20Neil deGrasse Tyson?

  Because the acceleration and the deceleration is what changes your relationship to the fuselage. If you jump up and come back down again.

• 33:31Chuck Nice?

  Right.

• 33:31Neil deGrasse Tyson?

  Okay, so yeah, that's why they can go 500 miles an hour. You may now remove your seatbelts and walk around the cabin, but it's just pulling in to the, to the, to the gate.

• 33:43Chuck Nice?

  Right.

• 33:44Neil deGrasse Tyson?

  It's going five miles an hour, but then it's going zero. Okay, that's enough to knock you over.

• 33:50Chuck Nice?

  Look at that.

• 33:51Neil deGrasse Tyson?

  So that, that's all I gotta say about jumping up and down in a damn airplane.

• 33:54Chuck Nice?

  That's cool. Well, I mean, now, when you hear that I have been arrested.

• 34:02Neil deGrasse Tyson?

  Tell them it's a science.

• 34:04Chuck Nice?

  I'm just letting everybody know that this was a science experience. I did it for science, people.

• 34:09Neil deGrasse Tyson?

  We'll get a GoFundMe to get you out of jail.

• 34:12Chuck Nice?

  Get my bail, that's right. Get my bail money up, people. Because we know what we have to do now.

• 34:20Neil deGrasse Tyson?

  So, another fun thing I used to do, I'm too old and tired and crickety for this. When I was a kid, in an elevator, like we're up in the city, so half my life is in elevators. If the elevator's going up and it's about to stop.

• 34:36Chuck Nice?

  Right.

• 34:37Neil deGrasse Tyson?

  You jump just at that instant.

• 34:39Chuck Nice?

  Right.

• 34:39Neil deGrasse Tyson?

  Okay? When you do, you had the upward motion that the elevator had just before it stopped. So then, when you come back down, you fall a bigger distance than you otherwise would have. And it feels great. It feels like you go over a hill, you know, in a car.

• 34:59Chuck Nice?

  Yeah, yeah.

• 35:00Neil deGrasse Tyson?

  Or on a roller coaster.

• 35:01Chuck Nice?

  A roller coaster, yeah.

• 35:02Neil deGrasse Tyson?

  If you do it in the opposite direction, then the elevator's closer to you than your body thought it would have been, and you end up getting compressed.

• 35:11Chuck Nice?

  A little pancaking.

• 35:12Neil deGrasse Tyson?

  A little pancaking, right, right. But it's fun to do that, where you are in air while the thing you were attached to changes its speed.

• 35:23Chuck Nice?

  It's very cool.

• 35:24Neil deGrasse Tyson?

  Yeah.

• 35:25Chuck Nice?

  I like it. I like it.

• 35:27Neil deGrasse Tyson?

  So, so there you go. In case anybody comes up to you and wonders what's going on.

• 35:31Chuck Nice?

  Yeah. Why are you jumping up and down in a plane, Chuck? So now we know why. This is it.

• 35:39Neil deGrasse Tyson?

  Because they listened to this episode.

• 35:41Chuck Nice?

  Two reasons you were jumping up and down. One, clearly you are drunk. Two, you listened to StarTalk.

• 35:51Neil deGrasse Tyson?

  So there you have it. That's our trinity of things you thought you knew.

• 35:56Chuck Nice?

  Nice.

• 35:57Neil deGrasse Tyson?

  Chuck, always good to have you, man.

• 35:58Chuck Nice?

  Always a pleasure.

• 36:00Neil deGrasse Tyson?

  This has been StarTalk, Things You Thought You Knew Edition. Neil deGrasse Tyson, as always, keep looking up.