Pamela: if you re not in one of those places, you re happily going to end up in some sort of orbit g

Gravity is always pulling you down, but there are places in the solar system where gravity balances out. These are called Lagrange car trailer rental seattle points and space agencies use them as stable places to put spacecraft. Nature is on to them and has already been using them for billions of years.
Fraser Cain: Gravity is always pulling you down, but there are places in the solar system where gravity balances out. These are called Lagrange points and space agencies use them as stable places to put spacecraft. Nature is on to them and has already been using them for billions of years.
Dr. Pamela Gay: I have heard it said Lagr-ahunge points, Lagr-ahungian points, Lug-range points and Lug-range-ian points. So you know â€" go with it. Say whatever your local dialect dictates is correct.
Pamela: The basic idea is if you have a two-body system with two giant things â€" where giant can be defined on small scales, such as the Moon and the Earth would qualify, the Earth and the Sun would qualify â€" then you throw in something small (a test particle, a frozen pea, a satellite), you can look to see how the smaller car trailer rental seattle object is going to gravitationally interact with the larger object.
When you start to probe all the different places you can stick this test particle, there are some places that when you stick it there, it stays. In general, car trailer rental seattle if you take an object and you put it on an orbit around the Sun that s bigger than the Earth s orbit, it s going to go around the Sun a little bit more slowly. When you stick it on an orbit that s inside of the Earth s orbit from the Sun, it s going to go around the Sun more quickly than the Earth.
Pamela: That s where the magic happens. There are a few specific points â€" five of them to be exact â€" that if you stick an object exactly in one of these five points, the combined gravitational attraction of the Earth and the Sun gang up on this object car trailer rental seattle to keep it moving in lockstep car trailer rental seattle with the Earth as it goes around the Sun. If you re dealing with the Moon-Earth system, you can stick things car trailer rental seattle in the five specific spots that come from the combination of the Earth and the Moon so that it sticks there, following the Moon in its orbit around the Earth in lockstep.
Pamela: if you re not in one of those places, you re happily going to end up in some sort of orbit going around the object, but you re not going to be synced up with anything. For instance, the space shuttle at the space station right now is zipping around the planet every 90-100 minutes. The moon, on the other hand, takes 20-some-odd days to go around the planet.
If I move the space shuttle and the space station its attached to, out into gradually further and further orbits, and position it in just the right orbit in just the right period of time, even though it s not as far away from the Earth as the moon, it would still go around the Earth with the same orbital period as the moon. It s in one of these magical Lagrangian spots where the potential and kinetic energies of the systems balance out just right to keep it there.
Fraser: Right. car trailer rental seattle If you slowly move it out and don t necessarily have it in a perfect circular orbit, it might get caught into some weird, gravitational dance, and get thrown out of the system or hurled into the Earth or sent into orbit around the Sun, or…
Fraser: Right, car trailer rental seattle get turned into very elliptical orbits. So if you have a little space rock that comes into our system, in most situations it s going to crash into the Earth, crash into the Moon, get skewed away into an elliptical orbit or…
Pamela: Right. So Lagrange-1 is the point between the two masses that stays in sync with the smaller object. For instance with the Earth-Sun system, this is the point in space nearer the Earth that, if an object is plunked down in L1, it goes around the Sun in the same just about 365 day period that the Earth has. We will always have this constant line going Sun-object-Earth lined up like little soldiers.
Fraser: Yeah. If we move a little more toward the Earth from that point, it will still be going faster than the Earth will, but it will actually be going slower car trailer rental seattle than that point. Right? If that makes any sense. You re saying it goes in lockstep with the planet, so…
Pamela: Here s a different way of looking at it that s a little bit weird. If I take an object and put it the exact same distance from the Sun as L1, but I plunk it down so the Earth, Sun and this object form a right angle from above, that object is going to start going around the Sun with its own period that is way shorter than one Earth year.
Pamela: Now if I take that object and take it at that specific distance from the Sun at just the right moment so that you have Earth, Sun and this object in a straight line with the object between the Earth and the Sun, and then I give it just the right amount of momentum, it s going to travel around the Sun with the exact same orbital period as the Earth.
Pamela: The Earth is giving it that extra pull. Well, not so much an oomph as it s combating the Sun s pull. It s because of the Sun s mass that the object would normally car trailer rental seattle be zipping around so quickly. If you have the Earth pulling in the exact opposite direction, in a way philosophically, it s like you removed a chunk of the Sun. if you make the Sun smaller you can orbit it more slowly.
Fraser: I ve got an analogy. If you re diving and you re going to wear a weight belt to keep yourself perfectly stable, then if you want to go back up you could attach a balloon behind you that would start pulling you back up. You could balance it out with weights and balloons, with the Sun being the weights and the balloons being the Earth. The right spot is your Lagrange point. 1
Pamela: car trailer rental seattle Just like with the weights and the balloons, you have to get it exactly right or you re either constantly car trailer rental seattle floating or constantly sinking. With the Lagrange points, especially with the first three, you have to get it exactly right, or you re going to go flying out of it. These aren t stable locations to be. The spaceships we stick there have to have their own engines and they re constantly making their own corrections to stay in these places.
Fraser: Okay, so these spots, car trailer rental seattle although you can keep going at that same orbital speed, they re not stable. It s almost like you re at the top of the point of a needle, and you can fall any direction and have to fall out of that Lagrange point. The only way to stay there is to keep using your rockets.
Pamela: Mathematically they re what we call saddle-points. car trailer rental seattle In certain directions, you re going to fall right back down to the Lagrange space. If you re taking a marble and trying to balance a marble on a western saddle, if you move it toward the head or butt of the horse, the marble car trailer rental seattle will roll right back to the centre of the horse s back. If you bump the marble left or right, it s fallen off the horse. I know people (including myself) who have had the same experience of falling off the horse.
These are semi-stable positions. The spaceships we stick there have engines that make corrections to stay put. At the same time, it s so convenient to have something that isn t in the Earth s orbit, and is following us around the Sun. it makes communications easier. It s worth the expenditure of energy.
Fraser: Right, if you wanted to put a spacecraft there and didn t have the help of the Earth s gravity, you d have to fire your rockets non-stop, using tremendous amounts of fuel. Even though you ve got to do minor corrections to stay at that sweet spot, it beats having to fire your rockets non-stop o stay in that kind of position.
Pamela: So with the L1 spot, which is between the Sun and the Earth, that s someplace we stick things that are observing the Sun for us. What s cool is they re just enough car trailer rental seattle closer to the Sun that in a lot of cases, when there s a particle spray â€" a bunch of electrons headed our way from the Sun â€" they might hit SOHO that s hanging out at L1 a little bit before they hit Earth, about an hour earlier. That gives us extra time to protect our astronauts and put satellites into safety car trailer rental seattle mode, because SOHO can send us radio signals at the speed of light that these electrons are coming toward us at less than the speed of light.
Pamela: If you have a position between the Earth and the Sun, there s also a point that s on the same line but it s beyond the Earth. So you go Sun-Earth-object, and that we call L2 (ever so creatively).
Normally if you stick an object on an orbital path bigger than the Earth s orbit, it will orbit a little bit slower. Since you have the added pull of the Earth, it s like making the Sun a little bit bigger, so an object can orbit faster and still be stable at that greater distance. It s not entirely stable: just like L1, it s saddle shaped and you can fall off the Lagrange point. It s still a great place to stick things that have to make corrections because car trailer rental seattle it makes the communications easy.
For instance, the Herschel satellite, the Planck satellite, the James Webb Space Telescope are all candidates for the Lagrange-2 point. WMAP, the microwave anisotropy probe that has given us such wonderful information about the cosmic microwave background is hanging out at the Lagrange-2 point.
This is a good place to put things car trailer rental seattle that is protected a little bit from the Sun s light, by the Earth hanging out there. car trailer rental seattle It s in a nice safe place beyond the Earth, following us around an orbit, and because it s not orbiting us, instead orbiting the Sun, all the random junk that orbits the Earth is not in any danger of hitting these things in the Lagrange points. The radiation doesn t get there. car trailer rental seattle It s a nice safe place to stick things that work in the infrared and radio that need it a little bit quieter and a little bit darker.
Fraser: Our heat. Right. That would actually cause them some problems. car trailer rental seattle So if you keep them away from the Earth, they ll be cold, and will have fewer radio waves blasting them. They ll have a chance to observe better the state of what the universe car trailer rental seattle really is. At the same