Neil deGrasse Tyson Explains Why Some Info Is Need to Know

[Music] i can't wait to see what you've been thinking about now i know i just i thought i'd you know we touched on this in another explainer video it has to do with uh you you gave me the term you know i as an educator if i'm teaching somebody something i'm not going to give them all details all at once because that could be distracting you want to work your way in step by step right so there's certain there's certain rounds of information that you bring in once a person has mastered the previous information basically like you're on a need-to-know basis that's what you called it and i didn't wanna i didn't wanna agree with that fact but like that kind of what it is isn't it it's well it is yeah it's just like well why does that happen no that i'll never forget i had a calculus tutor my first year calculus chuck you needed a tutor i'm very decent i did i needed a calculus tutor uh and we went we went to the we got to a certain place and this is why i needed a tutor and he told me this is why i needed a tutor we would get to a certain point in the equation and i would say but why is that he would go bro that's calculus three just relax this is how it works and chill your armpits right and i couldn't accept that i was like no you gotta explain to me why that and he was like it worked so you were ready for the next round i don't know if i was ready for the next round i just wanted to understand why that that you couldn't and but anyway okay so we don't know whether had he explained the next rounds you would have given up calculus entirely and so that whether he was right exactly or whether you were ready for the next round and they were holding you back we don't know you know what i mean you know i'd like to think the latter but it could be the former would it be funny if he actually gave me like the most detailed explanation from calculus 3 as to why this is happening and i was just like all right that's it i quit we first hit this when we asked the question what um what is the path of earth's orbit around the sun okay now if like i said if you don't know anything about orbits or planets or solar systems you're just brand new you walked out of a cave you've been there your whole life i will say earth's orbit around the sun is a circle okay and because it's easy to think about a circle you can draw it you can wasn't it drawn that way anyway at one point oh it was uh planetary orbits were circles through and including copernicus yeah yeah they didn't become not circles until after copernicus copernicus famous work that put the sun back in the middle of the solar system all those orbits were perfect circles now you know you're learning man that if someone says earth's orbit is a circle you're going to say no you're going to tell me it's an ellipse a slightly flattened circle right okay uh let me tell you that earth is like a three percent ellipse okay so if i drew it and then i if i drew a three percent ellipse and then i drew a more elongated ellipse and i said which one best uh approximates earth's orbit you're probably going to point to the more elongated one because you heard that it's an ellipse also that's that that's the visuals that you were presented with when you look or exactly but but i'm just saying when you but a three percent ellipse if you draw it and you at a glance it looks like a perfect circle okay so so but you're right but they actually but wait let me just back this up for one second for my own comfort the actual orbit is indeed a three percent ellipse is that what you're saying correct oh yes okay well that changes everything because that looks like a circle it looks like a circle if if you're only three percent different in one direction than the other direction right are you even going to notice that not really that's my point yes actually that so i can draw that and draw a more elongated one almost everybody's going to point to the elongated yeah we know it's showing off that they know that we're an ellipse right and they'll be wrong in so doing okay so by the way right now i just found out that earth's orbit is a three percent ellipse i did not know that yes so at our closest we are like 91 million miles from the sun right and at our farthest about 94 94 million wow yeah that is that is very little wireless 94. movement that's not only that's three percent on a hundred three hundred wow yeah otherwise the sun would get really big in one season and really small in the i mean you don't see that no you don't right okay so now you come out of the cave and you say okay i got it it's a circle okay we uh is there more i said yes it's not actually a circle okay it moves a little closer to the sun and a little farther away we have a word for that it's called an ellipse and we can watch that happen okay so at this time of year measure the size of the sun on the sky i'll give them a little tool to do that and wait six months later and you find out it's smaller all right so we are closest to the sun in january and farthest from the sun in july okay and january is called perihelion and july is called aphelion there you go all right and people say well wait a minute if we're closest to the sun in january how come it's colder what all that means is a temperature on earth has nothing to do with how far away we are from the sun okay let me guess i'm taking a guess here so because the earth sits on a tilt of 23 degrees it's not about how close we are it's about where the sun is hitting us on that that tilt correct and so if you're tilted towards the sun the rays are much more direct wait a minute did you just say correct yes i did that's exactly correct get out so watch so if you tilt towards the sun um as we are in january then i mean uh sorry uh we are in july then the ground heating is much more significant and that's that's what takes us into summer meanwhile the folks in the southern hemisphere are tilted away away that's why they get winter when we get summer and then it switches i was really guessing okay very good guest i thought you were going to say well that makes a lot of sense chuck but yeah that makes sense in your head right okay so now that now they're all good with the ellipse and i say all the planets are in ellipses all right some are less so than others pluto is particularly elliptical in the long list of weird things about it and venus is particularly circular but everybody is some form of an ellipse okay so now we're good there and that's how that's where most people are that's where most people have been left absolutely but there's more okay all right if i act now will i also receive but wait so now what so uh earth and the moon orbit each other okay okay so we're not just sitting in one place with moon going around us the moon and earth each orbit their common center of mass okay okay now obviously the center of mass is going to be much closer to earth because earth has more mass and this is even if it sounds a little weird it's completely intuitive if you walk up to a barbell and they're more weights on one side than the other and i asked where would you have to pick it up so that you balanced it you don't want to pick it up closer to the heavy side closer to the heavy side and then you can get a balance point on that that's true for anything you pick up right if you want to find the balance point so what that means is earth's path around the sun is not a circle it's not an ellipse it's a loop-de-loop oh because it's doing the little merry-go-round it's with the moon it's doing the moon it's doing it it's doing the moon jiggle right okay that's that center of mass is a thousand miles beneath earth's surface in a line connecting the center of the earth to the center of the moon so the earth is not doing this it's not doing this it's like doing this right the center mass is inside its own yeah it's like it's like a it's like a black girl telling you off let me tell you you stuck listen to me you better listen to me when i uh you all know me you don't know me yes exactly like that chuck okay so yes it's basically a circle it's also basically an ellipse but on top of that ellipse are these loop-de-loops right okay and not only that okay the path that earth takes around the sun does not rejoin itself in the same spot so in other words it's not a closed orbit no all right so the point for so for example the point where we are closest to the sun that actually shifts every single year and migrates around the sun it's called the procession oh that is so so cool it's a so it's a whole other level so now i'll teach you about procession and i teach about how that works and the gravity torquing because we're not a perfect sphere where a mass is unequally distributed wait a minute gravity twerks a [Laughter] so sorry man that would be cool it wouldn't be cool no no if the moon mooned us with a twerk the moon is twerking up actually there's something called libration on the moon right where sometimes the moon's orbit it's a head of where would be on average and sometimes it's behind of where it is on average so you can see a little bit around on the other side right okay so if you look at sort of static camera shot video shots of the moon librating okay this is us looking but it's so the moon is actually doing this right it's the moon it's kind of it's doing a back and forth so maybe you can call that twerking vibration is moon twerking moon twerk nice all right so this is an example of if you want more and more detail you have to keep going right and it's a matter of what level of educational instruction is in progress that's wrong though that they don't come on everybody learns about orbits and you learn about it pretty much middle school high school right yeah for that first earth science or something science thank you and that's when you start taking them knowing about procession that is so cool yeah and i did not know this that is that is just a really you'd have a perception even without the loop-de-loops right so all of these are happening like all at once and so so the real truth is deeper and more complex and more interesting than typically whatever is taught on the first round that's all i'm saying and that is true for almost everything that's taught right so you can i'll give you one more example okay we gotta land this plane so if you ask me how wide is the sun that's okay yeah how wide is the sun uh on this it's 864 000 miles across okay okay uh you know not quite a million miles across all right all right and that's fine and if you look it up in a book it'll give you that number but wait a minute um the sun is a ball of gas right so where is the edge how are you doing the edge of that what it how is that what so well you say okay well we you know you take a picture and you put a thing okay well whose edge is that that edge that you see is the last point of light that had scattered on its way to the edge and then escaped the sun but that's visible light right okay other wavelengths of light emanate from the sun at different depths so if you took an x-ray picture of the sun you'll get a different dimension for how big the sun is than if you take an ultraviolet or an infrared so so when you just say how big is the sun you can get an answer that satisfies most needs but if you really want to know what's going on you have to get into the weeds right you've got to dig in and then say how are you defining it and how does that vary and how big is that difference and there are some stars that actually pulsate and to say how big is the star you have to say well i asked when asked me when where in its cycle do you want to know how big it is right most variable stars in the night sky that start this category star called variable because they get brighter and dimmer over on a schedule right they get bigger and smaller so some questions don't just have simple answers but but not every educator is going to tell you that at every point right so now i have to ask this because you talk about variable stars and you know we sit in a nursery rhyme twinkle twinkle little star we also look up at times and we see stars twinkling do we have time for you to explain why exactly do stars twinkle not in this explainer we got it we can put that in another one all right you know i can't put the whole world in the universe in 10 minutes here i don't know what you what what you know what do you what do you want from me i i'm only one scientist am i just gym i can't do it i can't do everything so the point is um ideas matter more than any of these details right and so yeah it's an important idea that the sun goes earth goes around the sun and the rest are details that's fine and that idea gets you to other ideas and so but without joking let me just say this what is so critically important about what you are saying is that when we look at the scientific method and we look at science itself um what it does is allows you to open your mind to the possibilities of change and the rigid thinking that most people adopt and say it is either this or that or who or they think scientists have rigid thinking right because that leads to people saying things like i don't want to wear a mask because quite frankly the science is junk and the reason they say it is because things have changed we know more so we change the way we present information based upon an increase in knowledge or an availability of more information correct and so so that's all correct but an important difference in most cases there are very counter examples of this but in most cases the extra information is an improvement on what you previously knew right it doesn't completely throw away what was previously learned or understood or researched so that's why i said with the orbit around the sun each next thing is a nuance on the previous one right right when i say this the earth is doing loop-de-loops you don't have to abandon the idea that it's an ellipse because the the loops are on an ellipse right and so so you can keep the and keep the nested infrared like the nested russian dolls there's more detail and and you can stop where you want and you're good with that sweet you got it right all right chuck we gotta we gotta land that plane okay well next time we get to know why stars twinkle yes all right chuck always good to have you always good to be here neil degrasse tyson signing off of course bitty keep looking

Channel: StarTalk

Views: 409,909

Rating: 4.9513135 out of 5

Keywords: startalk, star talk, startalk radio, neil degrasse tyson, neil tyson, science, space, astrophysics, astronomy, podcast, space podcast, science podcast, astronomy podcast, niel degrasse tyson, physics, Chuck Nice, need to know basis, levels of information, Earth’s orbit, Sun, Earth, circle, ellipse, loop-de-loop, libration, Moon, Moon twerking, precession, scientific method, what is classified information

Id: RQj0cxHJ4fc

Length: 16min 34sec (994 seconds)

Published: Tue Sep 08 2020

Reddit Comments

[u/GiantRobotTRex]

It goes deeper. Other planets also affect Earth's orbit. Not as much as the moon, but enough that it actually affects our climate. https://www.sciencealert.com/jupiter-venus-warp-earth-orbit-epic-cycle-lasting-405-000-years-milankovitch

[u/Rombartalini]

You are talking the thickness of a piece of paper in an orbit the size of a continent.