Neil deGrasse Tyson Explains the Lagrange Points

What’s a Lagrange point? On this explainer, Neil deGrasse Tyson and comic co-host Chuck Nice explain orbits, satellites, and Lagrange points in space.
Big thanks to today's sponsor, Henson Shaving. Head to www.hensonshaving.com/ and use code STARTALK at checkout to purchase your razor and get 100 blades for FREE.
What do L1, L2, L3 mean? We dive into the physics of how objects in orbit are actually falling. You’ll learn about these regions of stability and how the moon’s orbit help create them. How many are there? How do we use Lagrange points? Are there differences between them? We discuss where we put the James Webb Space Telescope and why it's important. Where’s the Discover satellite? We break down Lagrangian placements in space and the Trojan and Greek asteroids of Jupiter. All that and more on another StarTalk explainer!
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Science meets pop culture on StarTalk! Astrophysicist & Hayden Planetarium director Neil deGrasse Tyson, his comic co-hosts, guest celebrities & scientists discuss astronomy, physics, and everything else about life in the universe. Keep Looking Up!
#StarTalk #NeildeGrasseTyson
0:00 - Sponsored By Henson Shaving
1:48 - Introduction
2:25 - How Objects Move In Orbit
3:16 - The First Point Of Lagrange
5:22 - The Second Point Of Lagrange
7:05 - The Third Point Of Lagrange
7:51 - Why L4 And L5 Are Special
9:20 - The L5 Society
10:03 - Where We Parked The James Webb Space Telescope
12:07 - Where We Parked The Discovery Telescope
12:55 - The Unstable Lagrangian Points
14:11 - The Trapped Asteroids At Lagrangian Points
15:38 - Closing Notes

[@neildegrassetyson]

Hi Everybody, just noticed that around 10m28s into the video I say that Earth permanently eclipses the Sun at L2 point, keeping JWST in shadow. But that's not correct. Earth will eclipse the Sun at that location but not always where JWST meanders. (L2 is a big area in space.) JWST's built-in Sun shade is what will keep it shaded. Thanks to a bunch of folks in the comment thread for noticing that error. -Neil deGrasse Tyson.

[@Mrsirayrodgers]

Dr. Tyson... I emailed a question to the StarTalk email questionnaire and never got a reply. Just wondering, if I may ask your opinion on changing the units of time going forward in the future. I think my question was pertaining to a recent video you did on how time is relative and the response to Dr. James Gates video you did on "Proving Einstein right." Since planets can become distant planetary rock bodies, such as Pluto being recast from planet to rock body... can we change the unit of a "second" to the Banneker or give some extra homage to the unit measurement of time? Best Regards... -Siray

[@theduder2617]

You were not incorrect Neil. You merely used a word that some people have yet to properly define is all. There remains a level of an eclipse of the sun by Earth at L2 where JWT is located. The center of the sun's disk always has Earth essentially directly in between it and JWT. And since we know that not every eclipse is total, a partial eclipse throughout the entire orbit is still a "permanent eclipse". Just not a full eclipse of which those who mentioned it were thinking. They were more incorrect than you were Neil. For they did not understand that not all eclipses are total eclipses.

[@00Skyfox]

But _why_ are L4 and L5 stable? Seems like the gravity from the two bodies (Earth & moon or whatever other pair) would be pulling things at those two spots inwards like a pair of elastic strings.

[@thebeast5215]

@@HopDavid like what?

[@tvc1531]

@@HopDavid I think Neil has no issues admitting any mistakes he's made. In fact he pinned his mistake and explained his mistake: Pinned by StarTalk Neil deGrasse Tyson 1 month ago (edited) Hi Everybody, just noticed that around 10m28s into the video I say that Earth permanently eclipses the Sun at L2 point, keeping JWST in shadow. But that's not correct. Earth will eclipse the Sun at that location but not always where JWST meanders. (L2 is a big area in space.) JWST's built-in Sun shade is what will keep it shaded. Thanks to a bunch of folks in the comment thread for noticing that error. -Neil deGrasse Tyson.

[@fetamean]

Chuck is such a good other guy to have on the show. He's capable of understanding a lot of the actual science, plus he's really funny with his improv. He doesn't fail to make Neil laugh.

[@silentdrew7636]

He's Watson, only funny.

[@dominiquecarter5055]

CHUCK IS THE MAN. NOBODY PLAYS THE COMEDIC TIMER BETTER. CHUCK IS ALSO LEARNING WORKING ALONGSIDE DR. TYSON, HE'S VERY SMART, VERY.

[@SevenHunnid]

When i look at the top & see all the succesful people.. there is NO mexicans 😩I review weed products on my KZbin channel .. tryna make it out💯..

[@webfox1]

I've seen Mr. Nice go from hardly understanding Dr. deGrass Tyson to keeping up even though he can still be impressed. I've been a fan for years. Comedy and intellect or not exclusive parts of our minds. They both have it all.

[@livinginthisgalaxy7961]

And he's the only one who can interrupt Neil...

[@kittiruffle4488]

Chuck is on fire in this video. He makes such funny comments, he laughs until he cries. I love watching you guys. You two are so Awesome! You both put to such good use your teaching and comedy skills. Thank you!!! ;)

[@fiusionmaster3241]

Same bro

[@katicabogar24]

The bromance

[@KSNeo]

Hello dear Neil and chuck, as a french fan I gotta say, those impressions were… magnifique x) thanks for all the sweet science facts and the sweet jokes always a pleasure to learn something on this channel.

[@StarTalk]

French fan approved! Thanks for the kind words, glad you enjoyed :)

[@thebeast5215]

@Hollister David could you elaborate on these so called false histories?

[@waynewynnx7976]

@@thebeast5215 This David is most probably a flat earther or creationist believer, just by looking at his words and his comments on other vids and channels that he's following.

[@theduder2617]

@@waynewynnx7976 He is bar NONE, one of the most uneducated trolls the internet has ever known. You will never find anything factual with anything he says. And absolutely never will any level of education make it through his intentionally think skull which despises objective truth at all cost. He will almost never leave his own comment and will mostly only ever defecate upon other's comments which are based upon undeniable fact. He is a stalker in a sense. If you make the mistake of responding directly to him, he will locate ANY AND ALL of your social media activity in direct effort to attempt to insult and harass with nonsensical ramblings no one capable of critical thought can make sense of. To be honest, I believe that he believes ONLY in opposition, nothing else. He is convinced it grants him a personality. Matters not the topic, he only ever opposes without logical defense of his chosen opposition. He has called airplanes "non-existent". Claimed there is "no oxygen within Earth's atmosphere". And that lizard alien people have taken our brains, but never his. All because he came across a factual post or comment stating otherwise and no other reason whatsoever. It is STRONGLY advised to block him on every social media channel. Sure, it can be fun to poke holes in his nonsense. But that fun is quickly replaced with sheer annoyance, for he NEVER stops once he gets going. If you ignore one of his ridiculous responses, he merely continues tagging while offering increasingly more ignorant responses. And as with ALL internet trolls, he becomes entirely silent when face to face. He ONLY does this when he can falsely believe that his keyboard keeps him protected.

[@miroslavzikic]

I'm surprised Neil didn't mention the most interesting fact about James Webb's position in L2, and that is it's not put exactly in L2 because it would be in permanent shadow (and it needs sunlight to operate its solar batteries), but that it actually rotates around that L2 point in small circles, so it can strategically catch the sunlight as well.

[@YAMAHA_FAN.]

Ah yes finally- Space razors that's what I was looking for more then 20 years Now my life is complete

[@fiusionmaster3241]

Lol bro

[@BushidoBrownSama]

it really is the best a man can get.

[@lasentinal]

I am well pleased by these presentations. They are very informative in an entertaining manner. The fact that very complex ideas are presented in such a way, makes it easier for those of us involved in education.

[@lasentinal]

@@HopDavid I do not use the information, just the humour.

[@Goldengirl48]

@@HopDavid Please explain. What information is incorrect?

[@StarTalk]

We're glad you enjoy it! Cheers to you, fellow educator.

[@fiusionmaster3241]

Agreed

[@glennpearson9348]

@@HopDavid Good points, but you're being pretty nit-picky. At L1 the acceleration due to gravity is EXTREMELY low, as is the centrifugal acceleration. So, when you say the Earth's pull is much stronger than the moon's, that is technically correct, but both "pulls" are but the slightest of fractions that one feels near the surface of either body. It's a very, very weak game of tug o' war. As for the JWST's orbit around L2, you're spot on. Indeed, the diameter of the orbit is about the same distance as L2 is from Earth; a fact that I think is lost on most folks. NASA intentionally put the satellite into this L2 orbit to improve it's ability to image in all directions.

[@sebasprieto9673]

I love this show, it's the perfect blend of knowledge and humor! I love Neil's explanations and Chuck is just so fun 🤣

[@Gerard1971]

10:27 Neil is completely wrong on several things here: 1. At L2 the earth does NOT completely eclipse the Sun, the earth disk is smaller than that of the sun, also, the L2 point itself is not stable, it moves. 2. The James Web Telescope is NOT at L2, it orbits L2 as depicted in the diagram at 10:52, and the distance from L2 is so far away that it is NEVER in the shadow of earth, which means that the solar panel will always be able generate maximum power. Also, it doesn't need to be in the earth shade, because it has the 5 layers of sunshield to keep the temperature down on the side that has the dish and the instruments.

[@Izaguirre2002]

You are right Sir.

[@cynodont7391]

I think that his definition of L1 is also wrong. He says a 3:50 that L1 is where the gravity of Earth and Moon are equal (and in opposite direction so they cancel each others). This is an oversimplification because there is gravity at L1. It is defined as a point where Earth gravity is reduced by the Moon gravity thus allowing an orbit with the same period as the Moon orbit. For example, Earth-Moon L1 is at 85% of the Earth-Moon distance. The Moon gravity at L1 is 38% of Earth gravity and consequently the overall gravity is still 100-38 = 62% of Earth-only gravity (so not zero). If you plug 85% of the distance and 62% of the mass in the formula that gives the orbital period then they will cancel each others (e.g. 0.85^3 = 0.62) thus providing a orbit with the same period than the Moon.

[@cynodont7391]

He is also wrong when he says that the James Webb telescope was placed at L2 because at that location Earth permanently eclipses the Sun. That would only be true if JW was exactly at L2 but in fact it follows an orbit around L2 that is larger than the Earth-Moon orbit. I would not be surprised if JW was never going through the shadow of Earth. In fact, JW has solar panels so it probably requires sunlight to operate.

[@Drondrin]

And Lagrange was italian, he was born in Turin

[@doubleRprodutions]

You're totally right of course, however I think that is the flavour of this channel. If you want something more substantial PBS Spacetime is the one

[@NoOne-xy6iz]

10:30 I think Dr. Tyson has misspoken here. The James Webb has a giant orbit around L2 that never takes it through Earth's shadow. So the spacecraft is actually permanently in sunlight.

[@Izaguirre2002]

Yes Sir.

[@lorien544]

yeah otherwise there would be no reason for the solar panels or tennis court sized sun shield.

[@wooddogg8]

Thank you, I was looking for this comment

[@69edbear69]

Came to the comments to say this, happy to see you’ve done my work for me. I expected better from you, Dr. Neil!

[@jimberry7865]

Yes! The main benefit is that JWST does not have to shield its eyes from 3 heat sources (sun, moon, earth) in different parts of the sky. They are all hidden behind the one “visor”, the sun shield.

[@cloggedaorta]

This was brilliant, I always had a hard time understanding L2

[@dickwestheimer]

Friendly amendment(s): JWST is never in the shadow of the earth. It needs sunlight to power its equipement and reaction wheels. Also, JWST doesn’t sit right at L2, it *orbits* it.

[@fraliexb]

Must have a nitpick with Neil saying that the JWST is at L2 and the Earth is blocking the sun's energy from the JWST. But the JWST is orbiting the L2 point and the Earth isn't blocking the sun's energy because the JWST has solar panels for it's electronics.

[@timothyvenable3336]

I’ve been waiting for this explainer since the launch of James Webb! Definitely helps

[@StarTalk]

Do you think it's time to reinstate the L5 society?

[@ShawnRitch]

Absolutely !!!

[@andrewtorrens7790]

As long as it's not controlled by corporate interests...

[@jeanetjensen6474]

Help heal the world first before leaving, please 🙏❤🌍🌌

[@TikkyTakMoo]

Hahaha. I enjoy jumping up and down and burgers and milkshakes too much.

[@katrinamichelle8373]

Only if I can join too!!!

[@grandpachas1267]

Fantastic tutorial! I am almost 70 (years not months). In the circa late 1970's I attended a few "L-5 Society" meetings at SUNY at Buffalo (Go Bulls.....we did not have a football team back then). I never fully understood the Lagrange points until now. You explained this really cool phenomenon wonderfully and with some good humor too, thank you.

[@TikkyTakMoo]

Lagrange points have come onto my radar a few times, but I haven't had time to get more into it than the surface. I appreciate you scratching the surface and shedding some light. It catalyzed a few ideas lirking in myind! 🤭😄💙

[@fwd79]

I _knew_ of L-points but this was just a very brilliantly explained _explainer_ about L-points and I can not ever forget that now. Also Chuck was very much on point in this video, *loved* this video, thank you StarTalk for sharing. 😊

[@kirkwagner461]

Please correct me if I nitpick incorrectly. My understanding is that the JWST is not at L2 but is instead orbiting it. And that orbit is large enough that JWST is actually outside Earths shadow. The reason for that orbit is so that its solar panels (on the hot side of the heat shield) get sun light in order to power the scopes instruments. Being at L2 (even just orbiting that point) is needed because that point is always outside of the Earths and Moons orbit, so JWST can always look outward, without being blinded by light from its two nearest objects.

[@Izaguirre2002]

Right, and my comment was deleted as soon as I pointed that out.

[@Gerard1971]

@@Izaguirre2002 I just made a similar comment. It could be that your comment was deleted by KZbin, I've noticed that a comment is very likely to be deleted if you used copy/paste.

[@NoOne-xy6iz]

That's right! That was a mistake. The spacecraft is actually permanently in sunlight!

[@Izaguirre2002]

@@Gerard1971 I stand corrected, it had link to a NASA blog talking about the solar array deployment.

[@Izaguirre2002]

@@HopDavid Yes, it had a link to a nasa blog talking about the solar array deployment.

[@photogeNK]

That moment when Chuck understands something and Neil is pleased

[@bfgreg1]

I love Dr. Tyson's laugh, it's so fun and deep, and really conveys his genuine amusement, and pleasure. It's definitely infectious!

[@madman2096]

Awesome Lord Chuck. A perfect reference to an '80s card game! And thank you for giving us an understandable explanation of the LaGrange points.

[@davidkalmykov7811]

Chuck should do commercials more often... He's commercials are good

[@mozkitolife5437]

I keep watching because this channel respects intellectualism enough to add the comma in the thumbnail title.

[@DaellusKnights]

Aside from the fact that Neil and Chuck are immeasurably entertaining (mad love guys!), this video turned out to be more useful than I expected. I'm the science freak amongst my friends and family. While I've long since understood the LaGrange points, it's sometimes been tricky to visualize certain concepts when they ask me to explain what they see on the news and stuff. Chuck's grasp of everything along the way just knocks it out the park. Y'all really make life easier for me on a regular basis. 😁💖

[@mattevans-koch9353]

Always a fantastic and hilarious way of learning things with these two. Love them both.

[@StarTalk]

So glad you enjoy!

[@Chickenandrice485]

You guys are my sanity! Pure and simple. Thank you!

[@ReyBaker]

Like the little graphic of the Lagrange points the editor added in

[@shalabazertheboltstruck8645]

Just learned about the L points during the JW telescope and just can't get enough of em

[@salmaninayatullah3783]

Great video guys! Can you do another video on how JWST is not stationery at L2 but is orbiting it? Thanks

[@kirkthiets2771]

They both smoked a big fat j before recording.

[@pesticidepiam]

"lets think up a few things" its the little phrases like these that might go unnoticed to a lot of people that i love so much neil

[@solojammer9500]

Chuck must be the only comedian who always crys and sheds tears for his own jokes.

[@me_and_my_piper739]

Thank you for this video. Not only was it really fun, but it also filled in the blanks in my understanding of Lagrange points. I’m absolutely fascinated with rocket science, but I don’t have a background in physics, so I can’t thank you enough for helping me to fully understand many concepts that I’ve struggled with. Neil and Chuck are hilarious as well!

[@taliachetty5417]

I don't even skip the paid advertisements.. That's how much love I got for startalk

[@ginamcdonald7854]

This was one of the best videos! Interesting how those areas can trap asteroids and hold them there!

[@katrinamichelle8373]

My favorite STARTALK so far. Mr. Tyson, great explanation of the placement of the Web, and the humor👏🏾👏🏾👏🏾 Love you guys🚀🔭👩🏾‍🔬

[@katrinamichelle8373]

That’s an easy fix, make your own video explaining it your way🤷🏾‍♀️

[@anxee]

@@katrinamichelle8373 100%

[@user-cf2pl9uy5k]

Thank you for adding the Lagrange points image.

[@ChrstphreCampbell]

I’m so glad that there weren’t any illustrations in this video because you might’ve actually explained something !

[@Garrick4184]

love your guys talks I love the different ideas of a lot of things

[@misery978]

Man f*** all that noise from earlier on in this series this show would be nothing without you thank you for still being here Chuck. you bring a liveliness to the show that Neil would never be able to. hes a great man hes smart and he can hold his own but this show wouldn't be nearly what it is without Chuck Nice. Makes it worth the startalk

[@misery978]

@@HopDavid fair point. Also why i have more respect for chuck. He knows where he stands on all this so he only goes for a reach when a joke is there

[@rusteshackleferd8115]

Lord Chuck is half of the reason I look forward to these video's.

[@CoNteMpTone]

Whats the other half?

[@dorsewise9473]

when you laugh hard enough to bring tears... ALWAYS a great feeling!

[@LHSlash]

Chuck, The only guy that can convince me to change to a new shaving blade.

[@DobrinWorld]

So good to have you guys, you make my day + learning something very interesting and good, important!

[@robertgraybeard3750]

@@HopDavidan object at Earth-Moon L1 feels the Earth's gravity, the Moon's gravity, AND a centrifugal force because the E-M L1 point is moving at the Moon's orbital velocity.

[@nikorahmad]

This is really entertaining.. This show would be so awesome if there is animation provided. Because everyday people like me, need that to match the great explanation by Neil

[@azuran133]

Another year of Startalk and Chuck'll be ready for his PhD viva

[@willg3220]

2 minute add in beginning is disrespectful of everyone's time. Put it at the end. Dr Tyson is amazing

[@anthonyarmstrong1460]

That was quite amazing. Caught me an oh wow fact again, as in "oh wow" I didn't know that until just now. So much we don't know and learn if we don't listen. Amazing!

[@benhelm6212]

I was just explaining these to people at our last star party! Wish this video could’ve come out sooner to show off! Always fun

[@josephherron7671]

Now see, I thought I understood Lagrange points until Tyson started showing off. Thanks Neil for keeping me in check.

[@tardiscommand1812]

I've loved this channel for a long time now, and how it's so positive and has zero negativity.

[@1jfmurray]

James Webb orbit around L2 was explained in a previous Star Talk. I think its a little much to go into here and not necessary to understanding the topic but y'all is right!

[@bill1299]

15 seconds into the show you had me wanting to buy a new razor!

[@akashdeepsason5112]

Chuck’s funny comments in between makes learning fun…

[@MuhammadNaseer]

I have no idea why I come here, For science or for Comedy, Both are exceptional.

[@StarTalk]

Why not both!

[@nobunaga240]

I didn’t realise how important these Lpoints were for our exploration of the solar system. Thanks very much!

[@puliravichandra]

Been waiting for this topic since long. Finally!

[@Justacoustic79]

You guys need a prime time TV show right now. I would put the money if I would just have it. No doubt about it. Thanks for all the science and the laughs. You are great.

[@alexgespino]

Chuck is the best co-host ever!

[@LeakSpeak]

i ain’t buying hansen no time soon but thanks to chuck it’s on my radar

[@MKlukowski]

Great stuff. Love having Chuck around. Can't wait until the next one.

[@kissmyfloyd]

Damn Chuck was higher than me this time. So excited! I love y’all!

[@mollybell5779]

Didn't know that the James Webb scope was at the earth/sun L2. Absolutely brilliant. Thanks again, StarTalk, for making me just a little smarter. 😁❤️

[@mollybell5779]

@@HopDavid I was going to ask for a source, but looked it up myself, and it seems that the scope is not in Earth's shadow. Ty for the info.

[@biopetri]

Oh man, I love Neil's laugh and Chuck's face when he is laughing :D

[@Amprobiuss]

At first I was like ....i don't know how I feel about chuck....and the relationship between these two...but by the day he's growing on me and the chemistry is so on point....i mean...this is brilliant 😇😃

[@christophelombardi7810]

Well, I'm French (living in Ireland) and I won't send you any hate mail, don't worry. Great video, as per usual. Keep them coming.

[@adilsonsf]

I've figuered out details of Lagrage points. Thaks Neil and Chuck. :)

[@Zagy21]

Best Lagrange Points explanation ever.

[@Zagy21]

@@HopDavid Well, he oversimplified it AF that might be way

[@Zagy21]

@@HopDavid ook

[@benedictochieng2604]

Best 16 minutes of my life

[@scevernulirece]

Thanks for the explanation, just add some diagrams in your videos. I think most of us viewers need that to understand these complex topics

[@kriskrumanaker4315]

Thank you. That made more sense than I've heard it before. And it's pretty amazing to boot!

[@StarTalk]

Awesome to hear that! Glad you could enjoy it.

[@bradjantzi4452]

Such a good bunch of actors! Love it!

[@kevinbihari]

Doctor tyson, Love the work you do as a science comunicator making it accessable to the masses. Would you please explain why l4 and l5 are stable. How coreolis action keeps stuff there and what the smaller of the 2 objects (moon in earth moon e.g.) has to do with that. I have read that the angular velocity changes "so that" it stays in place. How and what does the smaller object do? Also, l4 is dragged. Is l5 pushed? L1 is easiest to understand. Tug of war like chuck said. But i have been tought that centrifugal force is a psudo force. Is it then so that in order to stay in the same position, an object on lagrange point 2 needs to orbit at a higher speed, so the moon ads that bit of energy to its rotation? And it subtracts that from l3l?

[@CaliforniaBushman]

Maybe my favorite KZbin thumbnail of all time as an Amateur Astronomer.

[@RadioactiveLobster]

I recall seeing a really cool animation of Jupiter's effect on asteroids orbits. It was easy to tell where they were.

[@stupidape]

Thanks for explaining.

[@hitomi7922]

I was wondering why we didn't keep JWST at L4 or L5. I'm guessing cause we don't want it to get wacked by random asteroids that fall in the gravitational sink? Also, do solar systems and galaxies have their own level of lagrangian points with other solar systems and galaxies?

[@liranzaidman1610]

Can you have an episode on what it means for humans to live in higher dimensions based on the String theory?

[@networkl00p]

Thank you for taking the time to do these very informational videos. I have been learning more and more about lagrange points and had a question. Using the Moon and the Earth, if you place an object at L4 or L5, I don't understand how these can be stable. As the Moon orbits earth, I believe the the L4 point would get closer to the sun so wouldn't the suns gravity impact the L4 point? If it does, is the additional pull from the sun just not enough to pull the object away from L4? Same could be said for L5 but on the trailing side of the orbit.

[@aarond3657]

As the moon's orbit is between the earth and sun, the earth and sun are both pulling on the moon in opposite directions. When the lunar orbit is furthest from the sun, then the sun and earth are working together to keep it balanced.

[@networkl00p]

@@HopDavid Thanks! How bad does it affect stabilization at the L4 and L5 moon/earth points?

[@klaxoncow]

Well, yeah, "the three body problem" is ultimately chaotic. And so no system of three (or more) objects can ever be truly stable. Because, like, whatever object you place at a Lagrange point itself has mass - and therefore gravity - and it's now a three body system. So, now, adding this third object into the system - to create a Moon-Earth-Satellite system - you've got to consider the satellite's gravity on the Moon and the Earth. Yes, in practice, this is so infinitesimally small - as the satellite is tiny compared to the vast sizes of the Moon or the Earth - that we just fudge it and pretend like it's zero. But, technically, it's not exactly zero - just very, very, very, very small - and it is having this tiny minuscule effect. And that's where Chaos Theory kicks in, because no matter how tiny that non-zero difference is, it's accumulating over time. So, like, eventually, over very long celestial periods of time, it will add up to something significant. Gravity, as far as we know, has no limits on distance. But it attenuates according to the inverse square law: Twice the distance away then it's going to be four times weaker, three times the distance then 9 times weaker. Thank you, Mr. Newton for working that one out. So, really, every object in the universe is gravitationally affecting every other object in the universe. It's just that, over immense distances, that gravitational influence is so infinitesimally tiny, we fudge it and just treat it like it's zero. But, technically, it's not exactly zero. And this is where Chaos Theory comes in, because even though it's tiny, tiny, tiny in magnitude, it's accumulating up as time passes, and, eventually, after an insane amount of time, the butterfly's wings will cause a tornado on the other side of the galaxy. So, in that sense, nothing in the universe is truly stable. It's impossible. But, you know, in practice, we grossly simplify. Even though these things are technically non-zero, they're so damned close to zero that we just act like they are zero and ignore them. You can't practically take account of every single object in the whole universe when you're plotting a course for your satellite. And the point is that, in practice, you don't need to. The gravitational influence of Alpha Centauri - the nearest star to Earth - is so infinitesimally tiny, that we can safely just treat it as if it's zero (technically, it's not zero - gravity, as far as we know, extends forever - but it's so unbelievably close to it, we can totally get away with the simplification of treating it as if exactly zero). Every asteroid. Every particle of dust, even. Every single atom of hydrogen just floating out there by itself somewhere. They all have mass, and therefore have gravity. But when it's really tiny and really far away, then - inverse square law - it's so close to zero, we can treat it as if it were exactly zero. And, you know, just ignore it. There's a joke quote: "In theory, there's no difference between theory and practice. In practice, there is". And this is an example of that. In theory, everything with mass is exerting gravitational influence on everything else with mass - every object in the whole universe is pulling on every other object in the entire universe - but that's an impossible calculation to make. But, in practice, nearly everything - except for the big and close stuff - has negligible impact on your calculations, so you can throw away most of it, pretending like it's exactly zero (because it's so damned close to zero, it's really not going to change the conclusions of your calculations in any way). So, Lagrange meets Chaos Theory, and the real truth is that no location anywhere in the universe is truly 100% "stable". But, ah, it's close enough. For all practical purposes, it's so close to "stable" that, ah, we can treat it like it is. Or, more precisely, it's "mostly stable" and then we can give the satellite a thruster and some fuel... and we can then "correct" any tiny drifting away from perfectly stable. It's always a simplification, in the sense that we treat it like a "two body problem" or a "three body problem" and so forth, for our calculations. But, in reality, every object gravitationally influences every other object in the whole universe, so it's always a "every-object-in-the-universe body problem" in truth. But you can't practically deal with that. And, in practice, you don't need to. Just focus on the big and close objects, which have the lion's share of the gravitational influence, and act like everything else is zero. Alpha Centauri is having a gravitational influence on the Moon. But it's so ridiculously infinitesimally tiny, it's effectively meaningless and we just ignore it. It's close enough to the right answer. It's close enough to "stable" to be practically useful (and a retro-thruster can just fix any "drift" that occurs over time). There's the mathematical theory we work out in our calculations. But then there's also just being practical, in an engineering sense, of saying, ah, that's close enough. it's mostly right and who cares about our calculations being 10 atom widths out? It's good enough to be useful, and we can "correct" for it with retro-rockets. Basically, as the shepherd says to his sheep dog: "that'll do, boy. That'll do". In theory, all these calculations could go to infinite decimal places of precision. But, in practice, you can't pragmatically work to those levels of precision - we can't even measure things that precisely - and there's an "error range" where it just doesn't matter. If your satellite is 3 microns off where it should be, this really won't make any useful difference to anything. It'll do. It's close enough. We can work with this. It's always a simplification, but it's more than good enough, practically speaking. Like, maybe this satellite would, over a billion years, drift away from the Lagrange point. But, like, the satellite is not going to still be working in a billion years. As long as it's good enough for the decade or so that we're actually actively using it, then, ah, "that'll do, boy". If you like, it's the difference between a theoretical mathematician and an engineer. For the engineer, it's close enough. I can work with that. It'll do, for the purposes we have in mind. It doesn't have to be infinitely precise, just close enough that we can actually get the job done. So, yeah, in theory, every single object in the whole universe is contributing to the calculation. Yes, all of them. Everything with any mass at all. Even a single lone atom floating out there in the vast oceans of nothingness between galaxies. Every last bit of it. Anything - and everything - with mass has gravity, and gravity, as far as we know, extends forever. BUT, at the same time, gravity falls off by the inverse square law. So that's one over the square of the distance. Multiplied by its mass, so very tiny things contribute almost nothing. You get the picture - the gravitational influence of anything tiny or really far away falls off in an exponential way to effectively "so close to nothing, we might as well treat it as nothing" in very short order. I have mass. Therefore, I have gravity. But, like, my contribution to the Sun-Moon-Earth system? it's not worth considering. But, technically speaking, it is there. It's just so uselessly tiny, we can safely ignore it. So, in all of this talk of Lagrange points, you can introduce "but what about the Sun?" or "but what about the planet Venus? The planet Jupiter? The Oort Cloud? The Magical teapot that floats between Earth and Mars?"... and, technically speaking, they're all having some gravitational influence. As I say, every object in the whole universe is affecting every other object in the universe. You can literally extend this logic to encompass absolutely everything. But there's no point. Only the big and close things really make any serious difference to the conclusion, and you can safely disregard everything else and be so close to the correct answer that, in practice, it doesn't matter. If you like, every calculation we make has an "error range" on it. But if that "error range" is only a few microns or even millimetres then, in practice, who cares? As long as it's within tolerances, it's good enough. It'll do. We can practically work with that.

[@adrianwulff2608]

This was very interesting and insightful though I would have liked a little bit about how you can use the Lagrange point between Mars and the Sun to create a magnetic field that can protect Mars against solar wind.

[@louisrobitaille5810]

That's... not possible. You can't just "create" magnetic fields to protect entire planets. That's just science-fiction.

[@adrianwulff2608]

@@louisrobitaille5810 that’s true, i didnt formulate it very well. What I meant to say was the hypothesis about creating a magnetic field around mars to help it being terraformed, but it’s true sadly we don’t have the technology quite yet…

[@louisrobitaille5810]

@@adrianwulff2608 We'll never have it... This will always be science fiction. The only way to create such a magnetic field would be to create a make a dynamo out of Mars' core. That's how all the massive magnetic fields in the universe work, e.g. the Earth's, the stars', and even dead stars remnants' like pulsars or more specifically magnetars. For funzies and reference, the Earth's magnetic field is measured in microteslas whereas an average magnetar is 10^15 teslas. A tesla is the unit of measurememt of the strength of a magnetic field. A microtesla is 10^-6 tesla.

[@janwar7]

perfect timing going to france friday.

[@nekkantisriharsha99]

Hey Neil and Chuck, Greetings From India. Isro's Aditya L1 Targeting L1 point. So i want to know about these points. very well explained man. Love From India.❤❤

[@Chemy.]

I new about the Lagrange points but didn't know all this info about it

[@anxee]

I miss learning stuff. This is so good!

[@StarTalk]

Learning is fun!

[@anxee]

@@StarTalk oooooo doctor, doctor! I just read a couple of articles that JWST orbits L2, instead of ‘sits at L2 permanently being eclipsed by the Sun’. Now I’m more intrigued as to ‘how’ the unstable legrangian points (1, 2, and 3) can have their own orbital paths? Much like the JWST has of L2? Or did I mess that question up?

[@rtark52]

seems like you two are having way too much fun....thank you

[@cebolamaria]

Amazingly interesting! Thank you!

[@cujokid27]

Best ZZ Top voice! LA Grange (with a twist) "Rumors spread round, about this planet now. About space between the planets... You know what I'm talking about. Just let me know, If you wanna go, To that hole out in space, They gotta nice asteroids, A how how how." Love the explainer videos! 😆 sorry it's what I thought of when you was talking about Lagrange points!

[@supersportblitz]

Chuck you make this show great.. science is now educational and fun

[@xxkillmmmbbaaaxx2553]

Gotta say that im impressed at how much french Chuck knows lol. Its my main language up in canada, montreal. On that note, bonne soirée! :)

[@noclue4341]

thank you Neil , thank you chuck. i always wondered what those point are ! amazing and funny explanation

[@EliasBac]

I’m French and Chuck’s caricatural French accent kills me everytime 😂😂😂

[@StarTalk]

Yes! Approved by a French fan. Thank you!

[@GoPatriots]

Science, humor, and French accent! A perfect combination!

[@paulruiz8150]

Thanks guys for explaining us what in the world is a Lagrangian point ! It makes total sense now ! Just, can someone explain the L4 and L5 points please ? I still don't understand them. See you soon guys, bye !

[@robertgraybeard3750]

@Paul Ruiz - check the diagram at en.wikipedia.org/wiki/Lagrange_point#Stability_2 What ever is at L4 or L5 is a tertiary orbiting the primary-secondary system with centrifugal force balancing the combined gravity of the primary-secondary system.

[@DavidMKyalo-it1ok]

This video was magnifique!

[@CZPanthyr]

I should know by now to never take a drink of water during an Explainer Episode! I just had to learn that lesson again. Fortunately, nothing got an ice water shower and I did not choke to death.

[@rolandschoenke1840]

Chuck was on fire today

[@Aken0o]

Merci pour cette émission ;)

[@spidersj12]

A Lagrange Point is a location where you listen to ZZTop. L4 and L5 is where they keep rouge horses... because they're stable.

[@aaronmillon3620]

Another GREAT SHOW.

[@WasabiSniffer]

Welp! This is cool. And now I understand the James Webb telescope a whole lot better