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15-07-2017, 11:59 PM
So...
Say 5,000 years from now we've been farming asteroids and the whole planet is one big metropolis. We've built steel and concrete buildings ontop of each other for centuries. All fueled by space mining.

Not a 100% sci-fi situation, it could theoretically happen.
So my question is. Would bring outside materials (ie: iron from asteroids) and centuries of compacting it down and building ontop of old buildings/infrastructure etc.. increase the Earths gravity so that it's noticeably different from today's gravity.
Because there's more stuff and so should be more gravity right? Have by bringing back moon rocks have we increased the planet's gravity my a near infinitely small amount?

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16-07-2017, 03:14 AM
RE: So...
(15-07-2017 11:59 PM)earmuffs Wrote:  Say 5,000 years from now we've been farming asteroids and the whole planet is one big metropolis. We've built steel and concrete buildings ontop of each other for centuries. All fueled by space mining.

Not a 100% sci-fi situation, it could theoretically happen.
So my question is. Would bring outside materials (ie: iron from asteroids) and centuries of compacting it down and building ontop of old buildings/infrastructure etc.. increase the Earths gravity so that it's noticeably different from today's gravity.
Because there's more stuff and so should be more gravity right? Have by bringing back moon rocks have we increased the planet's gravity my a near infinitely small amount?

Volume of the Earth = 6.37x10(to the power of 6) For the sake of easy calcs let's assume we built over the oceans too...

The volume of buildings covering the whole surface up to 838 metres (highest building as far as I know) made of concrete (again for simplicity it would be SOLID concrete) so use your own imagination for doors, windows etc.. would be... 4.274638x10(to the 17th power)

Concrete weights about 2400kg per cubic metre so.. that would weight about...and I'm drunk and my calculator is either broken or I don't remember how to use it...

But my calculations show...NO, we cannot add enough to the earth's weight to make a difference in the gravity.

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16-07-2017, 04:46 AM
RE: So...
Also a small problem with your idea of buildings all touching the stratosphere is the simple fact that building materials (not to mention people and furniture ect) all have mass, we have no materials strong enough, nor engineering techniques capable of sustaining that intense weight across such a large span. Add to that if we were able to discover a material strong enough and light enough and engineering methods that could allow such tall buildings, then we would need to keep MOST of the planet reserved for plant life/animal life if for no other reason than to ensure we have an atmosphere, water, protection from radiation, and in general to keep Earth from looking like Mars. The idea of any planet becoming like Coruscant from Star Wars is simply untenable by any conceivable standpoint. It would require us to be able to manufacture atmosphere artificially and control our environment to a very high degree. Not to mention food supply problems having so many people and such limited space for creating food. While we will continue to advance and I won't completely rule out the possibility that we could one day build such a thing, it's unlikely and Unsapiens math would come into play after that. So.......


I think you now have your answer.

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16-07-2017, 04:55 AM (This post was last modified: 16-07-2017 04:58 AM by EvolutionKills.)
RE: So...
Not to mention, unless these super structures were solid, you'd actually most likely experience slightly less G force the further you got away from the Earth's core. The force of gravity decreases with the square of the distance.

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16-07-2017, 07:07 AM
RE: So...
And don't forget - until we work up spacecraft that operate on something other than Newtonian physics - the planet will also be losing mass from the equipment used in mining, the craft to get it there, and the vast quantities of propellant needed....

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16-07-2017, 10:45 AM
RE: So...
I actually looked up a few articles about whether the earth's mass is changing and most seem to say it's losing mass.

Apparently there's an estimated 40,000 tonnes of space dust that falls to earth every year but there's also an estimated 50,000-95,000 tonnes of material going out into space each year (mainly light elements like hydrogen & helium)

So it could stand a bit of weight gain from our space mining operations.

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17-07-2017, 04:45 PM
RE: So...
(15-07-2017 11:59 PM)earmuffs Wrote:  Say 5,000 years from now we've been farming asteroids and the whole planet is one big metropolis. We've built steel and concrete buildings ontop of each other for centuries. All fueled by space mining.

Not a 100% sci-fi situation, it could theoretically happen.
So my question is. Would bring outside materials (ie: iron from asteroids) and centuries of compacting it down and building ontop of old buildings/infrastructure etc.. increase the Earths gravity so that it's noticeably different from today's gravity.
Because there's more stuff and so should be more gravity right? Have by bringing back moon rocks have we increased the planet's gravity my a near infinitely small amount?

More mass = more gravity

So, yes, if you add mass to the planet you do increase the strength of it's overall gravitational field.

Noticeably? Not so much.

For example, the Earth gains about 3x10^7 kilograms per year in mass from meteoroids and other space debris impacting it.
Even if it didn't also lose mass (which it does), that only represents about (5.0x10^(-16))% the mass of the planet.
If that rate of mass gain went on for 2,000,000,000,000,000 years, it would amount to about 1% of the planet's mass.
That's about 440,000 times longer than the planet has existed, to date.

This question is like the one an ornery physics prof. put on our final exam in special relativity. He asked us to calculate the relativistic change in mass of a baseball, traveling at 90 MPH from a fastball pitch. Since the class was *special* relativity, he generously allowed us to ignore acceleration.
There actually is a mass increase, but it is so minute that without logarithms it happens so far left of the decimal point that the average calculator doesn't support the number of zeros needed. Meaning you have to do at least some of the math by hand (we didn't have logs on calculators back then...).

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17-07-2017, 05:05 PM
RE: So...
(17-07-2017 04:45 PM)Dr H Wrote:  There actually is a mass increase, but it is so minute that without logarithms it happens so far left of the decimal point that the average calculator doesn't support the number of zeros needed.

Your other left?

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18-07-2017, 06:45 PM
RE: So...
(17-07-2017 05:05 PM)unfogged Wrote:  
(17-07-2017 04:45 PM)Dr H Wrote:  There actually is a mass increase, but it is so minute that without logarithms it happens so far left of the decimal point that the average calculator doesn't support the number of zeros needed.

Your other left?

Heh, yeah, that one. Blush

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18-07-2017, 06:58 PM
RE: So...
This thread is giving me images of Bladerunner in my head.
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