What Are The Lagrange Points?
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There are places in the Solar System where the forces of gravity balance out perfectly. Places we can use to position satellites, space telescopes and even colonies to establish our exploration of the Solar System. These are the Lagrange Points. Support us at: http://www.patreon.com/universetoday More stories at: http://www.universetoday.com/ Follow us on Twitter: @universetoday Follow us on Tumblr: http://universetoday.tumblr.com/ Like us on Facebook: https://www.facebook.com/universetoday Google+ - https://plus.google.com/+universetoday/ Instagram - http://instagram.com/universetoday Team: Fraser Cain - @fcain Jason Harmer - @jasoncharmer Chad Weber - weber.chad@gmail.com Created by: Fraser Cain and Jason Harmer Edited by: Chad Weber Music: Left Spine Down - “X-Ray” https://www.youtube.com/watch?v=4tcoZNrSveE Being stuck here on Earth, at the bottom of this enormous gravity well really sucks. The amount of energy it takes to escape into the black would make even Captain Reynolds curse up a gorram storm. But gravity has a funny way of evening the score, giving and taking in equal measure. There are special places in the Universe, where the forces of gravity nicely balance out. Places that a clever and ambitious Solar System spanning civilization could use to get a toehold on the exploration of the Universe. These are known as the Lagrange Points, or Lagrangian Points, or libration points, or just L-Points. They’re named after the French mathematician Joseph-Louis Lagrange, who wrote an “Essay on the Three Body Problem” in 1772. He was actually extending the mathematics of Leonhard Euler. Euler discovered the first three Lagrangian Points, even though they’re not named after him, and then Lagrange turned up the next two. But what are they? When you consider the gravitational interaction between two massive objects, like the Earth and the Sun, or the Earth and the Moon, or the Death Star and Alderaan. Actually, strike that last example… As I was saying, when you’ve got two massive objects, their gravitational forces balance out perfectly in 5 places. In each of these 5 places you could position a relatively low mass satellite, and maintain its position with very little effort. For example, you could park a space telescope or an orbital colony, and you’d need very little, or even zero energy to maintain its position. The most famous and obvious of these is L1. This is the point that’s balanced between the gravitational pull of the two objects. For example, you could position a satellite a little above the surface of the Moon. The Earth’s gravity is pulling it towards the Moon, but the Moon’s gravity is counteracting the pull of the Earth, and the satellite doesn’t need to use much fuel to maintain position. There’s an L1 point between the Earth and the Moon, and a different spot between the Earth and the Sun, and a different spot between the Sun and Jupiter, etc. There are L1 points everywhere. L2 is located on the same line as the mass but on the far side. So, you’d get Sun, Earth, L2 point. At this point, you’re probably wondering why the combined gravity of the two massive objects doesn’t just pull that poor satellite down to Earth. It’s important to think about orbital trajectories. The Sun is here and the the Earth is orbiting around it. The satellite at that L2 point will be in a higher orbit and would be expected to fall behind the Earth, as it’s moving more slowly around the Sun. But the gravitational pull of the Earth pulls it forward, helping to keep it in this stable position. You’ll want to play a lot of Kerbal Space Program to really wrap your head around it. Sadly, your No Man’s Sky time isn’t helping you at all, except to teach you that hyperdrives are notoriously finicky and you’ll never have enough inventory space. L3 is located on the direct opposite side of the system. Again, the forces of gravity between the two masses balance out so that the third object maintains the same orbital velocity. For example, a satellite in the L3 point would always remain exactly hidden by the Sun. Hold on, hold on, I know there are a million thoughts going through your brain right now, but bear with me. There are two more points, the L4 and L5 points. These are located ahead and behind the lower mass object in orbit. You form an equilateral triangle between the two masses, and the third point of the triangle is the L4 point, flip the triangle upside down and there’s L5. Now, it’s important to note that the first 3 Lagrange points are gravitationally unstable. Any satellite positioned there will eventually drift away from stability. So they need some kind of thrusters to maintain this position.
Comments
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No, the forces of gravity don't balance out at any of the Lagrange points. At L3 and L2 both the central body and orbiting body pull in the same direction. L4 and L5 are equidistant from the central and orbiting body, therefore the pull of the central body is stronger than the orbiting body's tug. There is a point between the central and orbiting body where gravity balances out -- but this point doesn't correspond to the L1 point.
There are three forces at play. The third force is a pseudo force, actually inertia in a rotating frame. What we used to call centrifugal force. It is in this 3 man tug-of-way where the forces balance out. -
THANK YOU!! IT'S SO EASY TO UNDERSTAND!
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Would the Earth - Moon system have similar Lagrange points as the Earth - Sun system, or would that not work due to the Moon being tidally locked to the Earth? Thanks!
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Actually Lagrange was Italian, but whatevs.
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Ah how how how how.
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Yet another awesome video!
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I had a question that was prompted by one of your previous videos. I know that our understanding of "dark energy" or "dark matter" is very incomplete, but with it's apparent repulsion force, what would happen to a black hole that "ate" a bunch of dark matter?
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I got a question why don't astronauts put bar magnet to protect them from solar radiation
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Rogue one is out soon
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Great Video Man, Incredibly entertaining :)
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It would be a better idea to concentrate on a Moonbase and utilization of the Lagrange Points instead of just steamrolling for Mars. Patience wins over desperation every time!
Also: cut all those uncooperative trees down so they don't interfere with the SCIENCE!!!! -
I first learned about Lagrange points from Gundam Wing. I'm very proud of this.
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New idea - As we know, iron doesn't fuse. Would it become a black hole if it surpass a certain mass? What if you throw 2 solar masses of iron (as one huge iron-ball) on a solar mass black hole. What would happen? Thanks for your always interesting videos.
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You didn't really explain what makes L4 and L5 work.
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Space mining
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can you make a video about the metrioska brain ?
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I don't think Kerbal Space Program has L points. There is no N-body physics, you are only under one object's influence at a time. It's too bad.
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Fraser, perhaps you could explain, in a future video, why infrared light burns things while visible light doesn't, even though visible light is more energetic.
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Enjoyed your explanation, BUT I think you need to add some animated graphics or more descriptive pics. Using your hands isn't really going to cut it anymore, lol.
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I wanna go live in a self sustaining biome in space!
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