With the recent launch of the Nancy Grace Roman Space Telescope you will probably be hearing about Lagrangian Points so now would be a good time to have a look at what this is about.
The James Webb Space Telescope, launched in 2021 and also at a Lagrangian Point, is named for the administrator of NASA during the Apollo Missions that landed astronauts on the moon. This telescope is the successor to the Hubble Space Telescope, which has been a fantastic success that has far exceeded all expectations.
The Nancy Grace Roman Space Telescope is named for the NASA astronomer who is credited with making the Hubble Space Telescope a reality.
I consider these space telescopes as the culmination of the Space Age and really more important than actually putting astronauts on the moon. The main long-term benefit of the moon landings was the many technology spin-offs, from super-strong glass to powdered orange juice. The landings didn't teach us that much about the moon that wasn't already known.
The Cold War was a vital part of the Apollo Missions. The space probes that have been sent to photograph the planets are probably more important with regard to our Solar System but the space telescopes are more important to our learning about the universe overall.
The great advantage of putting a telescope in space is simply that it is above the earth's atmosphere. The best place to put a telescope on earth is on a mountain in a desert, so that it is above at least some of the earth's atmosphere and water vapor. But nothing is as good as having the telescope above the atmosphere altogether.
Aside from the Nancy Grace Roman and the James Webb Space Telescopes being much more powerful than the Hubble Telescope the main difference between them and the Hubble is their location in space. The Hubble Telescope is in a simple orbit around earth, at an altitude of about 500 km.
The Nancy Grace Roman Telescope, in contrast, will be positioned much further out in space, about a million miles or 1.6 million km away. The Nancy Grace Roman and James Webb Telescopes will actually be in orbit around the sun, rather than the earth, but will be in a very special place, called a Lagrangian Point, that will keep it in the same position relative to the earth.
Being in orbit around the sun, instead of the earth, will make it possible to keep one side of the telescope at the required very low temperatures. There will generally be a much better view from where the Nancy Grace Roman and James Webb Telescopes will be located, because the far side will always face away from the sun.
The great disadvantage of the location of the two new space teslecopes, as opposed to the Hubble, is that, since it is so much further away, repair missions will not be possible if something goes wrong. In the early days of the Hubble Telescope several such missions were necessary. On the new telescopes everything has got to work right the first time.
There is nothing really complicated about Lagrangian Points. When one astronomical object is in orbit around another, such as the earth around the sun or the moon around the earth, five Lagrangian Points are produced. These points are labeled L1 to L5 and are the points where there is some kind of balance between the two astronomical objects.
Because the smaller astronomical object will be in orbit around the larger one their Lagrangian Points will be continuously moving. The following image is so that you can see the Lagrangian Points of the earth moving around the sun. The red circle is the sun and the green dot at right is the earth. L4 is ahead of the earth in it's orbit around the sun and L5 follows it. Every astronomical object in orbit around another creates a different set of Lagrangian Points.
Only at the first two Lagrangian Points is the gravity of the earth and the sun actually equal. If we move toward the sun we reach a point where the gravity of the two are equally balanced, that is L1. If we move in the opposite direction, away from the sun, we reach another point where the gravity of the two is equally balanced, that is L2.
Gravity operates by the Inverse Square Law, an object at three times the distance will exert only one-ninth of the gravitational force. Gravitational force is proportional to mass. The sun is so much more massive than the earth that the gravity of the two balances at about 1% of the distance to the sun.
What is so useful about L1 and L2 is that an object in either of these positions will orbit the sun at the same rate as the earth, even though it is closer to or further from the sun than the earth. The James Webb Telescope will be positioned at L2.
L3 is the point on the earth's orbit around the sun that is diametrically opposite to where the earth is now located. If we draw an equilateral triangle, with the sun at one of the points and the other two points on the earth's orbit and the present position of the earth in the middle of the side opposite the sun, the two points other than the sun are L4 and L5.
L4 and L5 are both on the earth's orbit around the sun. L4 is 60 degrees ahead of the earth, as it moves around the sun, and L5 is 60 degrees behind it.
Unlike L1 and L2, the gravity of the earth and sun is not equal at L3, L4 and, L5. What is so important about all of the Lagrangian Points is that they are "preferred" positions in space. Objects, whether asteroids or satellites or clouds of dust, "prefer" to be located at Lagrangian Points than elsewhere in space. Objects sometimes orbit around one of the points, even though there is nothing at the point.
Jupiter has large collections of asteroids at it's L4 and L5. These asteroids are known as the Trojans. One group is ahead of Jupiter in it's orbit around the sun, and the other group is behind it. Any Lagrangian Point is designated by the two astronomical bodies and it's number, such as Jupiter-sun L4. We wouldn't just state "Jupiter L4" because Jupiter's moons also create Lagrangian Points in their orbits around the planet. Both astronomical objects that create the Lagrangian Points have to be specified.
Another thing that is so interesting, and useful, about Lagrangian Points is that objects in space can move from one Lagrangian Point to another with much less energy than would usually be required. There is a network, called the Interplanetary Transport Network, along which objects can move with a lot less energy than would usually be required.
Since there are more than two astronomical objects in the universe Lagrangian Points must be more complex than this. At the same time that the earth has Lagrangian Points in it's orbit around the sun, the moon has Lagrangian Points in it's orbit around the earth. We have looked at what we could call "primary" Lagrangian Points, but there must also be "secondary" points which share one of the two astronomical objects. Also, Venus is almost as massive as the earth and there are times when it is closer to the earth's L4 and L5 than the earth is.
These rules of Lagrangian Points only apply when one astronomical object is in orbit around another and one object is many times as massive as the other. The same rules may not apply, for example, to a double or multiple star system where the stars were closer to each other in relative mass.
You have probably heard of a "geostationary orbit" but it has nothing to do with Lagrangian Points. The higher a satellite is placed in orbit the more slowly it revolves around the earth. At the same time the earth is rotating. This means that there must be a certain altitude where a satellite will orbit at exactly the same speed at which the earth is rotating. This means it will stay in the same spot in the sky overhead. This makes it very useful for communication satellites and is called a "geostationary orbit". The altitude of a geostationary orbit is 22,300 miles. But a geostationary orbit has nothing to do with Lagrangian Points.
The concept of Lagrangian Points fits perfectly with my theory of "The Lowest Information Point", December 2017. The universe always seeks the Lowest Information Point. Energy is really the same thing as information. We cannot add information to anything without applying energy to it, and we cannot apply energy to anything without adding information to it. Another way we can see that energy and information is really the same thing is in how we can make our lives physically easier, by way of technology, but only at the expense of making them more complex. We can never, on a large scale, make our lives both physically easier and also less complex.
So if energy and information is really the same thing, and the universe always seeks the lowest energy state then it also must seek "The Lowest Information Point", hence the name of the theory.
Part of "The Lowest Information Point" is that the universe "prefers" an equality to an inequality. This is because an equality, such as A equals A, contains less information than an inequality, such as A does not equal B. An equality is preferred because it contains only one piece of information, A, while the inequality contains two.
In the same way the universe prefers a balance to an imbalance, simply because it contains less information. Complexity is expressed as the value of the denominator when a number is expressed as a ratio or fraction. If there cannot be an equality then a balance of 1/2 is preferred over 2/3 or 3/4 because 2 is the lowest denominator.
This is why the Lagrangian Points are preferred points in space, because the gravity of the two astronomical objects is in some kind of balance, if not directly equal as at L1 and L2.
Reusing information brings about "The Lowest Information Point". The distance between the earth and the sun is information and L3, L4 and, L5 achieve "The Lowest Information Point" by reusing this information.
The so-called "Interplanetary Transport Network", there is a Wikipedia article about it, of a route through space that requires much less energy than usual because it makes use of Lagrangian Points. An object will require less energy than usual to move between Lagrangian Points. This reflects on my concept that what exactly a straight line is, defined as the shortest distance between two points, may be open to definition.
Another thing that is interesting is that some believe black holes to act as "doorways" or "tunnels" in space. Black holes have tremendous gravity. If the gravity of ordinary astronomical objects like the sun and planets provide a lower energy route through space by Lagrangian Points, then what might we expect the far more massive black holes to provide?
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