Can the sun be shaded by human hands?
We read it again and again: The earth is getting warmer and we have to take countermeasures. One of the possibilities we could think of would be to shade the sun so that we get less radiation, less energy.
We could either completely shade the sun or just partially put up a dampening film between them. The question that follows is: Is this even possible? And do we perhaps already have such a shield?
First some data:
Sun data:
diameter
1,392,700 km
Distance to Earth
149,600,000 km
Earth data
diameter
12,756 km
Moon data:
diameter
3,476 km
Distance to Earth
384,400 km
The size in the sky can be specified by the angle between the outer edges. The formula is size = sin -1 (radius/dist)*2
So we calculate: Apparent diameter of the Sun in angular degrees: 0.524784604
Apparent diameter of the Moon in angular degrees: 0.518108242
Because of the similarity, there are solar eclipses, sometimes ring-shaped, sometimes complete (because the moon orbits around the earth) and always over a small area on the earth. So we know how we could block out the sun - we try it in our minds.
However, the moon is in Earth orbit, the occultation would not remain over the sun. Just as the solar eclipse only lasts a few minutes, the shadowing would also be over quickly.
If we orbit the earth more closely, the orbital period becomes shorter and the shadowing also becomes shorter: the ISS, for example, orbits the earth in approx. 93 minutes at an orbit altitude of 400 km. But even beyond the Moon's orbit, the shadow must orbit us, otherwise it will simply fall on the Earth or the Moon. Basically any orbit around the earth is unsuitable.
In order to permanently shade the sun, we need a position that lies between the sun and the earth, in such a way that our sail does not drift to the side, i.e. it does not revolve around either the sun or the moon. These fixed positions are called Lagrange points after the researcher who calculated them. For each pair of celestial bodies that orbit each other, there are five areas where the gravitational forces and the centrifugal forces cancel each other out. One of them is called L1 and is exactly between the two, i.e. where we want to set up the shading system.
The point L1 between the Sun and the Earth is 148,110,000 km from the Sun, which is 1,490,000 km from the Earth. With an apparent diameter of 0.524784604°, the required diameter is 27,294 km. This corresponds to an area of 585,096,056 km². We would actually have to add the Earth's diameter, but we won't do that.
We use the thinnest possible film - https://pe- Folie.eu/ Folien-weiche/ offers 100 m² of film with a thickness of 50 µm, which weighs 2.78 kg. Cling film is approx. 14 µm thick. If we take a third of that, we are approximately 5 µm or 0.278 g.
1 km² is 1,000,000 m², so the entire film on one km² weighs 2.78 t. The entire project, if we only use extremely thin film, weighs 1,626,567,036 tons.
The largest rocket we have is the Satu5C5Crn V, which can carry 133 tons, so we need 12,229,827 of them to get the load into space. During the starts, the windows were broken in the nearby towns, so it's pretty difficult to start them secretly. In addition, with this rocket we were only able to afford 17 missions with the US budget.
So we can safely assume that we don't have such a shield. Even if we were a factor of a thousand more efficient than what I calculated, we wouldn't be able to put up the shade sail, and at a factor of a million more efficient it would still be almost impossible.