Things You Thought You Knew - The Ancient Planets

0:00This is StarTalk, a Things You Thought You Knew edition. Of course, I got Chuck Nice with me. Chuck? That's right. I don't think I know anything. That's why I'm here. That makes you a perfect co-host. That's it. That's right. For this excursion. I'm happy to be here. All right. Not knowing a thing. Let's get this party started. Welcome to StarTalk. Your place in the universe where science and pop culture collide. StarTalk begins right now. Chuck got another explainer. Awesome. The diameter of the sun. Okay, this sounds boring.

0:43The diameter of the earth is about 8 ,000 miles. Thank you. And that's it. Because I did not know that, so I'm already good. It's about 8 ,000 miles. About 8 ,000 miles. Okay. And from that, you can know the circumference, if you remembered pi. Okay. The circumference equals pi times the diameter. Okay. And how much is pi? 3.14 something-something. Exactly. So a little over three. Right. So you multiply 8 ,000 miles times three and a little bit, you get at least 24 ,000 miles around and some change. It's about 25 ,000 mile circumference. Right. Okay. Fine. And I think we did on a separate explainer that the diameter of Earth pole to pole is less than the diameter of Earth at the equator.

1:30I think we talked about that. Earth is slightly flattened. It's spheroid, I think. Yeah, that's what an oblate spheroid is. You're flattened top to bottom. Okay, yeah. The sun is also shorter top to bottom than across its equator. Interesting. Not by much, but it's measurable. Okay, so when someone asks, what's the diameter of the sun, what answer are you gonna give them? Are you gonna give them pole to pole? Are you gonna give them across the diameter? Are you gonna take the average of those two? I just want you to appreciate that when you look up a numerical answer to a question, depending on what it's answering, the question might not have an actual answer.

2:16We just have to sort of set the rule. The diameters are going to be across the equator for everybody. What's the diameter? What? Oh, that's, you know. You need the high frequency. Right, you need, oh. You know, that lets them know that it's not exact. Okay. Yeah. So now you say, all right, let's say we do equator. Now you look up at the sun with filters. Then you see the sharp edge, right? The edge of the sun. The sun has an edge, okay? But wait. Uh-oh. The sun is made of what? Plasma. Plasma, it's just gas, basically, okay? Plasma gas. When was the last time you saw gas have a sharp edge to it?

2:56Well, that'd be my Uncle Daryl.

3:04when that smell moves across the room, it has sharp edge. Sharp edge. You either in it or out of it. Oh, man, you know. It's time to go. The spherical ball that is the sun, the oblate spheroid that is the sun, we speak of an edge, but that's an edge made of gas. Right. Okay. How do you even have that? That's my point. It's like Earth's atmosphere. Right. Where's the edge of Earth's atmosphere? No, there's no edge. Right. It's gas that becomes sort of thinner and thinner. You know you reached it when you're like.

3:41So when we see the sharp edge of the sun, in practice we were referring to what's called the photosphere. Ooh. The photosphere is a layer of the sun's atmosphere which is the last point of contact with the photon trying to get out of the sun. Ooh, okay. And now the photon can move at the speed of light in a straight line. Until that point, it was bouncing back and forth among other molecules and other atoms and other particles. By the way, had that photon been moving in straight lines, you'd be able to see deep inside the sun. Oh. That's what light moving in straight lines means. Right, yes. Why is a window transparent to you?

4:29because the light moved in a straight line through the window. Right. But then I smoked the window. What do you do when you - Frost. I frost the window. Right. And now the light, I can't get through. I got to jiggle a little bit. I'll still come through, but I'm not in a straight line. Right. You cannot see through the window. No, yeah, the window's lit up, but you can't see what's on the other side. The light's coming through, but it's not a straight line. It's not a straight line. Okay. All right. So the photon gets to this place, an edge where it can now escape for free. There's not enough above it to keep bouncing around.

5:01Right. That edge is the photosphere, and that is our definition of the edge of the sun. That's only using visible light. Oh, God. Okay. I knew there had to be a twist to this. So we are visible light biased. Right. I don't mind that, but don't declare that this be the diameter of the sun if the diameter of the sun is simply what your own damn eyeball is. Right. Wait, oh my. Right, so if you look at the sun in X-rays, it has a different diameter. Really? X-ray photons are coming from a different place. A different surface. So we are biased, and I think we need the occasional reminder that we are eyeball biased.

5:52Diameter of the sun is where the visible light comes from, and specifically yellow light, Right in the middle of the spectrum. Red, orange, yellow, green, blue, violet. Right in the middle. Let me keep going. Go ahead. There's a layer of sun's atmosphere on top of that. On top of this photosphere? Yes. You know what that's called? Mm-mm. The corona. Oh, yeah, okay. That's part of the sun. That's part of the sun. Why is your diameter not including that? Right. That's part of the sun. The corona, depending on where the sun is in its cycle, can be really big or really small. So that changes on an 11-year cycle.

6:29But wait, the sun has a magnetic field. That extends beyond the corona. Right. That's called the magnetosphere. Shouldn't that be part of the diameter of the sun? It's part of it. Part of the sun? It's part of it. All right? Yeah. All I'm saying is, if you seek the truth, my son, be aware that the truth has many faces. One face may deceive you into thinking that it is the face of the answer to that question. Let you not be blinded by how authentic its truth may seem because others will be speaking their truth quietly and clearly and you must listen to them as well. Do I have to snatch a pebble from your hand now?

7:27Wow. Snatch the pebble from my head. Wow, you got some quick reflexes, man. All right. You do it, you do it. Oh, snap! You have some really, like, uncannily fast reflexes. Like, there shouldn't be. Whoa!

7:53You are not ready, my son. Come back another time. Okay, one last fun fact about the sun. Okay. All right. If we're about 8 ,000 miles across. Right. If you look up the diameter of the sun, it'll give you something like 864 ,000 miles. Something like that. Jesus. Okay. All right. So now, let's round that down just so the numbers come out fun. Call it 800 ,000 miles across. It's 100 times bigger. It's 100 times. 100 times. 100 times across. Across. So you can take Earth and position it 100 times back to back, belly to belly, and you'll span the width of the sun. Wow. Okay, 100 times. Now, by the way, that's about the size of sunspots.

8:36So the sun has blemishes larger than Earth. Than the Earth. Just so you know. Jeez. All right. So now, if it's 100 times across, that means it's also 100 times deep. Deep, yeah. It would be 100 times top to bottom. So how many Earths could fit into a hollow sun? Can you just pour into the sun? Pour into the sun. That's 100 times 100 times 100. Give me what that number is. 100 cubed.

9:09Thank you, Chuck, for that precise response. 100 times 100 is 10 ,000. Right. 100 times 10 ,000 million. And then? That's it. I did it three times already. Okay, right. So the sun were hollow. You could pour a million earths into it. Wow. And still have room left over. Damn. Yep. But yet for millennia, people were walking around saying, the sun and the moon were like the same thing on the sky and we're the center of the universe. If you read Genesis literally, the earth was created before the sun and the moon. And when we came to these realizations over the millennia, over the centuries, it was like, no, we're not making earth first and then assembling something a million times larger and have it orbit the earth.

9:57Right. And anyhow, the universe works. Yeah, it doesn't, yeah. We're not that special.

10:16I'm Ali Khan Hemraj and I support StarTalk on Patreon this is StarTalk with Neil deGrasse Tyson

10:34So Chuck, did we ever have a conversation about leap days? I have a vague memory, but maybe it just slipped into other explainers. I was going to say we've discussed it, but not specifically. Not on its own terms. It's not like, son, I'd like to talk to you about leap days. Oh no, come on. The time has come. You're old enough. Because you're old enough now to know about leap days. People seem to be mystified by it. Right. The day just shows up in the calendar. Well, because, yeah. It seems very arbitrary. It does feel arbitrary, like some high council decided that February needed a day. Exactly.

11:14So it's very simple. So here's Earth, tipped on its axis, spinning. So the time it takes Earth to spin once on its axis, what do we call that? A day. A day. Are you sure? Well, it should be. It should be. Why not? I mean, why not? Okay. That's a day. That's a day. So now, Earth also goes around the sun. Right. How long does that take? That's about a year. It takes exactly a year. Okay. Exactly a year. All right. That's the definition of a year. Of a year. Okay. We made a trip around the sun. There's no law in the heavens that requires the rotation of the Earth to divide evenly into the time it takes Earth and goes around the sun.

11:55That's true. Okay. They're totally unrelated phenomena. Right. Okay? Exactly. So we count days by rotation of the Earth. Right. We count years by revolution around the sun. And it turns out a year lasts 365 of these things plus one-fourth of a turn. Okay. A quarter turn. It's 365 days and six hours. Six is a fourth of 24 hours. Okay? Yeah. That's how long it takes Earth to go around the sun. What are you going to - That's too much. That's too much. So what are you going to do with the six hours? Right. It's too much. By the way, it's six hours this year, and then the next year, it's six hours added to the previous six hours.

12:37Right. Now you got 12 hours. Now you got 12. You don't know what to do with. Right. So it's a half a day. Are you going to celebrate the new year on a moving six-hour platform? I'm thinking about that. No, no. It's interesting, right? I'm kind of thinking about that right now. You don't celebrate at midnight. You celebrate at six in the morning. Oh, no. Forget it. Then again, that depends. That's a hell of a party. That's a hell of a party, man. You know what I mean? So the first of those years, you celebrate at 6 a.m. Right. Next year, 12 a.m. This is on the 366th day, right? And the next year would be like 6 p.m.

13:11Right. All right? And the next year, back at midnight. Yeah. Okay? I'm just saying. That'd be kind of cool. It'd be kind of dope. Yeah. It would be kind of dope. Just like, yeah. What time is New Year this year? Right, in order to not have to do that, let's go back to ancient Rome in the Julian calendar. They figured this out. Of course they did. And they said, let's pocket those six hours. Right. Don't tell anybody. Okay? And we just celebrate the new year six hours early, but nobody knows. Nobody knows. It's just a complete day, you do it at midnight, we're good to go. Right. Okay, you pocket that.

13:48There you go. Next year goes by. Sounds so much like the Roman Senate. So you've got the first year goes by, you pocket the six hours. Right. Second year goes by, pocket the six. Pocket another six. Third, pocket the six. We're up to six, 12, 18 hours. Our pockets are getting full. The fourth year comes around, you don't pocket that. Right. Because now you've got a full 24 hours. You've got a full 24 hours. You put the day back in the calendar. Boom, there you go. There it is. Look at that. The leap day. Empty your pockets on that day. Every four years, you're throwing a leap day. And you give it to the neediest month.

14:19Right. Okay? Exactly. I mean, why not? Right. Which, of course, is Black History Month. That's the neediest month. I think in ancient Rome, it wasn't Black History Month yet. Oh, yeah. I'm sure it was.

14:32It was Slave History Month, right? Right, exactly. For all, everybody. Because I don't care who you were in Rome, you was a slave. You know what I mean? Like, wait a minute, man. Is that a white slave over there? Hey, brother, this is Rome. So there you have it. That is the fundamental origin of a leap day. Right. But here's what happened. Okay. It turns out it takes a little less than 365 days and six hours to go around the sun. Oh, God. It's not an exact six hours. Of course. Well, it couldn't be, right? Because that would make too much sense. Right. That would make too easy. Even that would be technically evenly divisible by like a whole number of hours.

15:13Exactly. It's a little bit less. Romans didn't know this. Right. Of course. They didn't know this. Well, can you blame us? We're using sundials, sir.

15:23Oh, you and your fancy astrophysical atomic clocks. What happened then, over the centuries, there were days accumulating that were not accounted for. Oh, they lost days. No, no, no, they were, yeah, yeah, the days that should have been reckoned and were not. And they were not. Okay, so, all right. So, the consequence of this is that key moments in the calendar related to like the universe end up shifting. So the first day of spring, the vernal equinox, March 21st, over the centuries became March 20th, and then March 19th, and then March 18th, March 17th, March 16th, March 15th. And they were just living with it.

16:08What is happening in the spring, guys? Spring is just sprunging all over the place. We can't have spring sprung in February. Right. It was marching its way early in the calendar, century by century. Right. Okay? This was a concern. Why? Right. Because the Julian calendar, with its rules for Easter, Easter, because Christianity was now in charge. Right. Okay? So Easter, the definition was, Easter is the first Sunday. Right. After the vernal equinox. Right. Pope Gregory, we're now in like the late 16th century, so 1580s. All right. Pope Gregory notices that Easter is moving with the equinox because it was defined by the equinox.

16:54Right. And there was a risk that Easter would land on Passover. Oh, we can't have that. Can't have that. Oh, you know you can't have that. It was hard enough to get people might have otherwise been Jewish to be Christian. Exactly. Okay. Yes, exactly. Your Eminence, I believe the Jews have a plot to ruin Easter. Right. So you can't have that. Plus, think of what effort it took to call Sunday the Sabbath. He's noticing this and said, we've got to fix this. So he gets his smartest folks in his contingent. Wait, the Pope has scientists? Yes. Get out. Yes. Serious. Serious. Highly educated scientists.

17:35Okay. To this day, there's a Vatican observatory. Did you know that? I did not know that. Yes. The Popes, and who are they? They are the Jesuits. The Jesuits are the academic order among the orders of Christianity. Of Catholicism. Catholicism. Okay. As we're priests. Yes. And so they founded many of the Catholic universities that persist to this day. Right. Okay. For example. Okay. He tasks them to say, fix this. They study the movement of the sun, moon, and stars in the sky. And they say, we have not been properly reckoning leap days. And they conclude extra leap day had accumulated every hundred years.

18:11Okay. Okay. That's too many. And that was not reckoned. And that shifts the vernal equinox backwards in the calendar. Okay. All right. In order to fix this, they said, all right, let's jumpstart it. Put the equinox back on March 21st. Got to put it back there. Okay. That's where it belongs. And what you do with autumn days? I know. Okay. By then, it was on March 10th. Wow. Okay. So in October, 1582. October now. October. Okay. They're saying, time to jumpstart the system. All right. So? They took 10 days out of October. Look, dude, you're the Pope. You have the power to do this. I'm going to say that's too much power for one man to have.

18:52Just like, guess what, October? You just got cut. I'm sure the Pope sounded exactly like that. Like angry black man. Yeah. Guess what, October? Dominus is spittered to half the month. It's gone. A third of the month is gone. And you know why? Because that's when we owe rent. So they took 10 days out of October. Dang. So October 15th followed October 4th. Okay? Did I get my numbers right there or something like that? Yeah, yeah, yeah. And you have to, like, I don't know if that was the invention of amortization, but how do you decide what rent to pay? Right. You have to sort of get the fraction of the month, divide, multiply by your rent, but a fraction, and that's what you pay.

19:36Okay. We still stay with the four-year rule, except every 100 years, which is still divisible by four. Right. 100 is divisible by four. every hundred years, we take out the leap day that would otherwise be there. There you go. Now we're balancing out. We're balancing out. Nice. Okay? Nice. However, the Jesuits were badass. All right. They said, that undercorrects it. That undercorrects it by a little bit. Okay? I got to tell you, this moving New Year's Eve thing is looking real good right now. So, if you look at the undercorrection, now it's going to happen on an even longer timescale. So what you find out is, at what rate have you undercorrected it?

20:16Every 400 years, you got to put a leap day back in. Back in. Because 400 years is still on a 100-year cycle. Right. But every 400, you got to put it back in. Now, who is alive to remember to do this? That's what I'm saying. Okay. So, this was the amazing fact about the year 2000. Okay. If you didn't know what I just told you, you'd say, well, of course, it's a leap day. It's divisible by four. Right. No. You know how rare that leap day is? It's a century year divisible by 400. Right. That gets a leap day. 1900 didn't have a leap day. 1800 didn't have a leap day. 1700 didn't have a leap day. So no day put in.

20:55Okay, 1600 did because that was right after. It just happened. It just happened. Because 1582 is when it happened. Exactly. So 1600 still got the leap day put in. Behold the Gregorian calendar. Look at that. What a mess. No. Wait, wait. The Jesuit priests figured that out without a telescope. Oh, that's amazing. Telescope was not yet invented. So they just looked up at the night sky? Yes, and made measurements. And made measurements. Yes. Wow. Now that's impressive. There you go. Yeah. So the leap day simply makes up for the fact that we don't count years by whole numbers of days. And we got to throw in a day every four years and not every hundred years, but then back again every 400 years.

21:41Now, if you're born on a leap day. Oh, too bad.

21:47You got screwed. Okay, so the real way to do birthdays is to know exactly where Earth is in its orbit. Right. And celebrate that moment every year. Oh, there you go. And then you don't have to worry about what they call the day, what day of the week, what day of the month. It's the orbital time, how do you count in time around the sun? And that's your birthday. That's your birthday. And what also is weird is how precise we count the new year. Right. Let's go into Times Square or wherever. Right. And you see the countdown clock. Right. Okay. And then it hits midnight. But excuse me, it hits midnight for your time zone.

22:20For your time zone. There's 24 time zones. Exactly. All right? But 24 slices of the earth. Yeah. All right? So, and then they celebrate it and they celebrate it. There's nothing magical about the moment. We're not all celebrating the new year. Correct. Right. You're celebrating the new year where you are. Where you are. And that's it. Right. By an agreed upon calendric system. Exactly. The time frame. And if you're in Times Square, you probably missed it because you were peeing in a bottle.

23:10So, Jack. Yes. We haven't talked about planets in a long time. This is true. All right. I think we're overdue. Throwing a little extra planet pop culture. Can you recite the planets in order? In order? Yes. Like coming from Mercury. Okay. Right. And then Venus, Earth, right? And then Mars going out after that. That's a big one. That's Jupiter. And then you got Neptune behind Jupiter. No, you got Saturn. Oh, I'm sorry. How are you going to leave out Saturn? Saturn. God. We were Saturn, Neptune, and then, you know. Uranus, Neptune. Right. Uranus, Neptune, sorry. And then. No. No, and yeah. We're done.

23:50Uranus, Neptune, and then. We're done. The planet count over the years has fluctuated. Yes. To the ancients, there were seven planets. I will recite them for you. Okay. Mercury. Okay. Venus. Venus. Mars. Jupiter. Jupiter, Saturn, the sun, and the moon. All right. Now, I could see the moon being considered a planet because it's like coming and going. No, because the definition of planet has changed. In the day, planet was anything that moved against the background sky. Okay, so all the other stars are staying kind of where they are. Correct. And then you have these little - Fixed stars. Fixed stars.