As more and more objects are rocketed into space, is it possible that the mass of the Earth could be reduced? If so, could this affect the distance that the earth orbits from the sun?
My uneducated guess is that it would be negligible but I wonder if it can be measured.
Johnny
I’d think the amount of mass we launch out of our atmosphere is less then the amount of mass entering from meteors and such.
Good point, I didn’t even consider that the earth is accumulating mass constantly from shooting stars, etc. That’s another variable to consider and makes me think that the mass of the earth has been increasing naturally.
In terms of altering Earth’s orbit, I’m pretty sure space junk that’s merely in Earth orbit won’t affect it; I think that stuff would still be part of the total Earth system with respect to the Sun.
At any rate, Earth’s mass is about 5,973,600,000,000,000,000,000,000 kilograms; the International Space Station is about 390,908 kilograms. If we sent 10 million objects the mass of the ISS into deep space every year for 10 million years, the total mass lost would add up to less than one-thousandth of one percent of that of the planet.
Like math ever proved anything!
The “system” consisting of the Earth, the Moon, and all material gravitationally bound to either orbits the “Center of Mass,” or barycenter of the system. To mine, refine, process and fabricate material which will be launched into Earth orbit, or sent to the Moon, will decrease the mass of the Earth, and will affect the rotational velocity (and angular momentum) of the planet by an infinitesimal fraction of a percent, but will have no effect on our orbit around the Sun. The location of the barycenter may shift by a tiny amount, but all the mass which was part of the Earth is still counted when the mass of the system is considered.
In addition to negligibility of mass, and the fact that mass in Earth’s orbit is part of the Earth for such calculations, don’t overlook that the Earth’s mass is irrelevant to its solar orbit anyway. Such orbits are subject to Kepler’s Laws with the only free parameter being the then-unknown mass of the Sun.
I think the best chance to reposition the Earth would be deflect a large comet or asteroid to approach Earth closely. Unfortunately, to get the asteroid close enough for significant gravitational effect might pose risk. :rolleyes:
Didn’t Cecil, or the SDSAB do a column on this?
Basically, many meteorites crash on Earth every year. They add slightly to Earth’s weight, far more than the rockets we send up decrease it.
As for affecting our orbit, a more significant factor is that the Sun burns millions of tons of fuel every single second, thus becomes less massive over time, and it’s gravitational pull is less.
Thanks for making that point about Earth’s mass not affecting it’s orbit. I have some reading on Kepler’s Laws to do.
Johnny
Aren’t all these considerations about the effect of changing mass/gravitational attraction dwarfed by the effect of the Earth capturing a stray alpha particle, say, which happens all the time (i.e. cosmic rays)?
IOW, the electromagnetic force is some 10[sup]36[/sup] stronger than the gravitational. Doesn’t that mean that the effect of capturing an alpha particle and thereby changing the Earth’s net charge even if only for a moment is the same as the gravitational effect of capturing the mass of 10[sup]36[/sup] alpha particles (about 1.3 X 10[sup]10[/sup] kg if my arithmetic is correct, i.e. more than 10 billion kilograms)?
If the Earth and the Sun were entirely made up of charged particles of one sign, then yes, the electromagnetic force between them would be 10[sup]36[/sup] times larger than the gravitational force and we wouldn’t be having this conversation. But the force between two charged objects is proportional to the product of their charges, and the net charge on the Earth and Sun is much smaller than it would be if they were entirely made up of alpha particles. (The mass of the Earth is about 10[sup]51[/sup] times larger than that of an alpha particle; the Sun’s mass is 10[sup]56[/sup] times larger.) So unless a truly stupendous number of cosmic rays get dumped on the Earth and on the Sun, gravitational effects will continue to dominate.
Isn’t this only because the sun is much more massive than the earth? If the earth and sun were of closer in terms of mass the Kepler’s laws will not be accurate.
I once met a relatively well-known science fiction writer – gentility prevents me from naming him – who told me, in total seriousness, that the Apollo program had unbalanced the Solar System, by bringing several pounds of moon rocks back to earth.
The fact that we’d left several thousand pounds of lunar lander on the moon eluded him entirely. And the fact that vast amounts of tektites kicked up from the moon’s surface by meteor impact fall to earth also had no importance to him. It was the moon rocks that unbalanced the Solar System!
Sometimes, even the smartest people can be more than a little dumb…
Trinopus
Yes. Earth can be treated as a “test particle” of infinitesimal mass, but in general, the mass of both objects matter in calculating orbital period.
The Earth gains something like 400 tonnes of dust every *day *from space (based on an estimate of 1.5 x 10[sup]11[/sup]g / yr. So a bit of space junk is totally insignificant.