# Do satellites decrease the amount of solar radiation reaching Earth?

According to this website, there were 3,372 active satellites in orbit at the beginning of 2021. Furthermore, SpaceX is planning to launch 12,000 satellites to provide cheap internet for everybody, among other functions.

Does this huge collective quantity of objects (together with space trash) reflect away enough solar radiation to have a measurable effect? Could this affect earth's climate, mitigating climate change?

• Obviously the answer is yes, when they're between the earth and the sun. The issue is that they would reflect solar radiation back to Earth when they're behind the Earth but still in sunlight. I'm not sure you could even factor that but the effect must be more than zero Aug 25 at 17:16
• I was just about to message you about your changes. grammarist.com/style/earth gives a rough rundown that's in line with my thoughts. Capitalize specific names of things. So Earth the place is usually capitalized (it's maybe not 100% absolutely a law, but for me, looks very odd with it lowercase). Whereas, it is earth when we talk about just dirt in general. (Apparently to complicate things it is indeed lowercase when preceded by 'the'... as in "the earth is a sphere"... I guess that's a unique oddity in general, as we don't say The Mars or The JeoaprdyTempest at all. Sep 3 at 9:39
• Science is fairly similar... it's Science when it's a specific title, like of a subject in school (just like Chemistry, Math, or Cooking). Whereas when we talk about it as a general concept, it should be just lowercase. "This is a science site" ... "It took many years for me to learn the science that I know now." I know English is a complex language, it's not always cut and dry or consistent (and some is probably still evolving... Internet was once always capitalized, but not now). I still struggle to remember it's hablo español and cepíllate los dientes, so at least we struggle both ways! Sep 3 at 9:54
• I THINK both of these extend the same to British English and the rest of the English speaking world (though can't 110% guarantee it). I usually feel like the variation globally for English is a little less than Spanish, given Spanish changes an entire verb conjugation group and lots of vocabulary cross-Altantic (and even intraHispanic). But English US vs UK has enough little quirks (s vs z, er vs re endings... and even after spending 4 months there in the past 6 years and regularly listening to UK soccer/football, there'll still be words or phrase that surprise me because I've never heard them Sep 3 at 10:05
• @JeopardyTempest I need a long rest, and it would be nice I publish my first application 1st january. Feel free you or any rep user to edit any of my content. I will be disconnected until then. Sep 3 at 13:11

Does this huge collective quantity of objects (together with space trash) reflect away enough solar radiation to have a measurable effect? Could this affect Earth's climate, mitigating climate change?

No.

Suppose, instead of 12,000 tiny satellites, SpaceX was planning on launching 12,000 satellites the size of the International Space Station. The ISS, with its huge solar arrays, has a cross section of about 7,000 square meters (6,528 square meters for the arrays alone). Fun fact: This is about the size of a FIFA-sanctioned international match field. I'll bump up the size to 8250 square meters, the maximum size of a FIFA-sanctioned international match field.

The ISS blocks sunlight that would otherwise hit the Earth about half of the time. I'll halve the 12,000 satellites to 6,000 to reflect this. Six thousand maximum-sized FIFA-sanctioned international match fields results in an area of 49.5 square kilometers. The Earth's cross section to sunlight is $$\pi r^2$$, where $$r$$ is the Earth's mean radius (6371 km). This cross section area is $$1.275\times10^8$$ square kilometers. That's over 2.5 million times larger than those 6000 maximum-sized FIFA-sanctioned international match fields.

Summary: Even 12,000 satellites larger than the ISS would have a minimal impact on the amount of sunlight hitting the Earth. The 12,000 satellites SpaceX is planning to launch are orders of magnitude smaller than the ISS. The impact is in the noise.

• I found after asking SpaceX is reducing reflection to help astronomers. bbc.com/news/technology-52391758.amp Aug 24 at 14:31
• @Universal_learner they're doing that so that the satellites don't reflect light into the telescopes and obscure objects in outer space. Aug 24 at 19:02
• Not really asked, but just to add, satellites typically orbit around the equator (although some don't, eg. GPS, Starlink). Thus, it's unlikely the "shading" from satellites would be uniform across the earth. Aug 25 at 8:31
• @Universal_learner "Musk says" a lot of things..
– smcs
Aug 25 at 10:12
• @RalphBolton geostationary satellites (less than 600) orbit around the equator. I believe most others (about 1600 active satellites or 7400 "objects in orbit") don't. Aug 25 at 16:44

Yea,but by a mere infinitesimal amount. Earth as a rough sphere has a surface area of 196.9 million square miles or 509 Trillion square meters, add atmospheres thickness 100 miles up it's 200 million of exposed to solar light, 3700 random objects with a area of 5-10 square meters is 37,000 meters square, barely 0.01 square miles, so 1/16 billionth of the Earth's light is blocked by orbiting stuff.