this post was submitted on 16 Sep 2024
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Futurology
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I asked the same thing to a panel of JPL nerds years ago, and the answer was basically "We don't definitively know." , but some facts I hadn't thought about came out of it.
Earth's gravity technically doesn't change by any measurable amount in relation to the sun unless we send mass far enough away to not interact with Earth gravity anymore, and the vast majority of everything we've sent up is still in orbit.
The distance to the Sun can't be measured in any effective way directly, so they essentially measure the distance of Earth to thousands of other objects in relation to us and the Sun to come up with a usable number
The effective Gravity of Earth can't be reliably measured before the first instrumented measurements were taken at some point (I can't find when this was, but early 2000's I think). They can only tell from the first measurement if there are effective changes.
Knowing all of this, it seems bringing back millions of tons of mass to Earth is going to change SOMETHING.
Scientists say "We don't know for sure" when they definitively can't say the odds are zero. "Will flinging satellites out of the solar system change the orbit of the earth, causing it to plunge into the sun." "We don't know for sure." "Will setting off a nuclear bomb ignite the entire atmosphere?" "We don't know for sure." "Will running the Large Hadron Collider create strange matter that will annihilate the entire universe?" "We don't know for sure." The first question was asked by you, the other two were asked by senior officials at some point in the last 100 years. Even before they were asked, scientists were fairly certain that wouldn't be the result, but there was some small chance that it could, and scientists generally don't say "No" unless there is absolutely no chance something will happen.
Well, I think they were talking about the absolute difference between gravity or not of an object. It's not really subject, we just don't know at what point that happens because we've largely only been working with orbit made.
We lose thousands of tons of mass every year in the form of gases and gain a lesser amount in material from asteroids over the same period. The mass gain appears to have been quite dramatic, back when the earth was formed. Chaos would have reigned for a significant period after that, then we would likely have had a constantly diminishing amount of asteroid impacts. When exactly the earth went from a net annual gain of mass to a net loss is hard to say, but if you were to ask if the mass of the earth-moon system maintained an annual net zero mass change at any point, the answer would probably be "We don't know for sure."