Lets take earth and say it grew by around 20%. What would the ramifications be of this: On the weather? On its orbit? On the planets near? On the people living on it?
I've been having thoughts on my own about this, but I'd like to hear what other think of this.
If the Earth gains 20% of mass, you would have to redo the third Kepler's law. Meaning you would have to move the Earth farther away from the Sun and the year would become longer. So you would definitely have a colder climate because the Sun is farther now (not too much, I think. I'll do the math and report back.)
Edit: reducing mass of the planet could be done by a large pocket of anti-matter deep in the core of the planet, slowly annihilating with the matter. It could cause the same heat as the radioactive decay that is happening inside Earth. Of course this would mean that you are getting a gradually larger void inside the planet, which could mean collapse of the matter above.
Edit: here's the third Kepler's Law:
GM/4pi^2 = a^3 / P^2, where G is the gravitational constant, M are the combined mass of the Sun and Earth, a is the distance between Sun and Earth and P is the period of the Earth's path around the sun (1 year). If the Earth gains 20% of its mass, the combined mass of both bodies would be virtually the same due to the large mass of the Sun. Therefore, the change in a or P would most likely be non-detectable.
In cold brute math, this means:
dM/M = 3 da/a = -2 dP/P
The Mass of the Sun is 2*10^30 kg.
The mass of the Earth is 6*10^24 kg.
a of the Earth is 150*10^9 m.
P of the Earth is 365 days.
M means both masses combined but since the Sun has a million times more mass than the Earth, you can skip the Earth.
dM is 20% of Earth's mass, which means 1.2*10^24 kg.
This would mean that the distance between the Earth and the Sun would increase by 30 km or almost 19 miles.
The year would be longer for almost 10 seconds.
[This message has been edited by MartinV (edited December 12, 2010).]
The nature of the weight gain in your story will change things somewhat. Is it constant, such as a means of absorbing WIMPS may do? Or is it stochastic (i.e. variable with time) such as meteorite accumulation? Or perhaps it is periodic, such as accumulating the solar wind (the closer to the sun, the more it accumulates)?
Also, adding weight reduces the velocity (due to the conservation of momentum). This could destabilise the orbit, depending on the rate of weight addition and the cause behind it (remember an assumption behind Keplers's Law, though he didn't know it at the time, was that the orbits were stable). On the other hand, solar wind, for example, may add an outward momentum that offsets the reduction in velocity. This method may push the body outward, as Martin above suggested, to a new stable orbit. I'm not entirely sure which will have predominance, though, and we are talking very long time periods.
Planetary size change over a period of more than a thousand years would not be "noticeable" by the life. Succeeding generations would adapt to the increased gravity.
Man made structures would suffer. What was sufficient engineering for one level of gravity would collapse or be unable to handle normal loads at another.
Thrust calculations to get into space would become wrong. It would cost more to get into space.
As for the cause, Stars go around the Galaxy on different routes and rates compared to each other. Nebula do the same thing. All one needs is for the solar system to pass through a light nebula and acquire a lot of mass as it passes through.
AS for the size, I remember reading a piece by Isaac Asimov where he said that there are no planets in our solar system between 10? and 100 times the mass of our moon. The idea is that when a planet reaches a certain mass, it develops the gravity to hold volatiles, and then develops atmospheric mass rapidly.
Hey, just letting the imagination wander a bit.
Martin, very cool stuff Mon...
edit; read a 'Register' article about the moon shrinking, beginning to crumble in on itself.
http://www.theregister.co.uk/2010/08/20/moon_shrinking/
this may spark an idea or two!?
[This message has been edited by DRaney (edited December 12, 2010).]
I remember a Larry Niven gimmick involving dropping iron fillings in a vacuum set up between two teleportation gates. As their speed approached that of light, their mass increased, eventually enough to affect Earth (or whatever planet the gates were set up on). The mathematics of it eludes me, though...
quote:
Bigger than Jupiter sized planets found around other stars have shown the Kepler's law is just an observation, not an actual law.
Sorry, I don't buy it. Kepler's law is the direct result of gravity.
GM/4pi^2 = a^3 / P^2 +/- SFFF.
The new constant allows you to add or subtract the SFFF--the science fiction fudge factor, to make it work out. Relax.
I was thinking the planets gain weight through importation, which even with a massive operation it's going to take an astronomically long time. (Which would also leave other planets with less weight.)
If you want to see the effect of reducing the planet's mass, just input a negative dM in the above equation. You get negative da - the distance gets smaller - and positive dP - the period grows larger.