Futurology

1850 readers

68 users here now

founded 1 year ago

MODERATORS

A space elevator on Ceres (with today's tech) and the gravitational assist of Jupiter for returning payloads back to Earth, could allow us to start mining the asteroid belt costing just $5 billion. (www.universetoday.com)

submitted 3 months ago by [email protected] to c/[email protected]

23 comments fedilink hide all child comments

you are viewing a single comment's thread
view the rest of the comments

[–] faltryka 6 points 3 months ago (1 children)

An interesting thought that makes me ask a few questions.

How much of that dwarf planet would be in scope to return? I guess my completely ignorant suspicion is that it would be a small volume of highly valuable minerals, or minerals destined for space anyway.

Also, what about the mass we are moving off world today? Have all of our satellites and rockets and other space bound craft resulted in any measurable change to earths place in the solar system? I would imagine some leave only temporarily, but how much mass do we permanently shed?

[–] just_another_person 5 points 3 months ago (1 children)

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.

[–] [email protected] 2 points 3 months ago (1 children)

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.

[–] just_another_person 1 points 3 months ago (1 children)

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.

[–] [email protected] 3 points 3 months ago

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."