If Earth was destroyed, would the planets in our solar system realign?

Question

Would the rest of the planets move closer to the Sun? Would one of them become livable for humans?

Answer 1

The short answer is: No. the planets in the solar system would not significantly realign or move closer to the Sun and none of them would become more livable for humans.

Earth has about 0.0002% of the total mass of the entire solar system. So, anything that happens to it isn't going to have a huge effect on anything else in the solar system.

Also recall that gravity in the solar system is effectively Newtonian for everything except the most precise measurement of the perihelion of Mercury (which is adjusted in a measurable amount in general relativity because it is so close to the Sun which makes up such a huge share of the total gravitational effects in the solar system that the slight tweak for general relativity effects is detectable there).

This means that the gravitational force declines with the square of distance. So, objects more distant from Earth (e.g. the gas giant plants) are much more faintly affected by a change in the gravitational force arising from Earth than closer objects are affected.

As noted by HDE 2226868 in the comments and at this post the impact on Mars, a relatively close and relatively light neighbor would be on the order of 10^-8 m s^-2 of acceleration, the sort of slight tweak that a laser measurement before and after might be able to discern, but nothing that would meaningfully change the dynamics of the solar system. The impact on more distant and heavier bodies would be even smaller. The impact would also be much smaller than that (probably not even detectable with state of the art instruments) if Earth was blown up but most of its mass remained in the solar system in roughly the same orbit.

If Earth was destroyed, for example, by being broken up into little bits by a "death star" type weapon, or large, fast moving projectile, it would leave a lopsided asteroid/dust belt more or less where Earth used to be, so the impact would be small indeed, because most of its mass would be in roughly the same place.

Other scenarios for its destruction might have bigger effects depending on the gravitational or solar wind impact of the event that does Earth in. For example, one could imagine a fast moving primordial black hole hurling through space at a right angle to the plane of the solar system rushing through, gobbling up Earth in an instant, and moving along its way only slightly perturbed in direction, having as much of a gravitational impact on the solar system from its brief approach, swallowing of the Earth, and continuation on its path, as the absence of Earth from the solar system, per se, would have on the rest of the solar system's dynamics.

But Earth's mere sudden (physically impossible) disappearance wouldn't have much effect on anything else in the solar system except the Moon and orbiting satellites and space junk. This is very easy to model mathematically, but impossible to accomplish in real life. In a science fiction world one might imagine that this happened when a wormhole suddenly materialized near Earth (perhaps brought about by some handwavium mad scientists on Earth) and gobbled us up and closed again.

The only really interesting large body in the solar system that would be tossed around would be the Earth's Moon, which would could end up almost anywhere in the solar system depending on the precise mechanics and timing of Earth's obliteration. But, the Moon wouldn't have the raw materials to be more livable for humans no matter where it ended up relative to where it is now. It doesn't have enough organic material or water and doesn't have any meaningful atmosphere.

I suppose if the Moon were hurled in just the right way, its collision into something else might make that something else more habitable by virtue of the collision itself, rather than by changing its celestial mechanics. For example, if the Moon crashed into Venus that could conceivably cause significant changes in its atmosphere and planet's geology that might make it more habitable, although not all that quickly, in something like the same way that the proto-Moon crashing into Earth that formed the Moon and the Pacific Ocean did on Earth's ecology.

Any gravitational or electromagnetic solar wind effects of Earths destruction would propagate at the speed of light, not instantaneously the way that "the Force" did when Planet Alderaan was destroyed in the Star Wars saga, because in real life, nothing moves faster than the speed of light.

The Sun accounts for 99.85% of the mass in the solar system. The eight non-dwarf planets (including Earth) account for about 0.135% of the mass in the solar system (more than two-thirds of which is in the planet Jupiter). Perhaps 0.01% of the mass in the solar system is in comets.

The moons of planets, dwarf planets, asteroids, other meteroids and space dust, combined, account for something on the order of 0.005% or less of the mass in the solar system (i.e. about two parts per million) of which moons, dwarf planets, and the three largest asteroids in the main asteroid belt of the solar system account for a very significant share of this combined mass.

Assuming that dark matter is the correct cause of the phenomena attributed to it, the total amount of the dark matter in the solar system (defined as a sphere at a distance from the Sun equal to Pluto's most distant orbit) is on the order of the mass of a single decent sized asteroid, but distributed almost uniformly within that volume.

Answer 2

The only natural way to re-arrange the planets (while removing/pulverizing Earth), would be to toss in something with huge gravity - like a black-hole traveling at really high speed. But I don't think you'd be able to get your effects nicely (and you're certainly not going to get another Earth anytime soon: Earth is the result of billions of years of modification by life, as well as some very specific conditions). I think it'd be more like throwing a hand-grenade into chess-game, and expecting the undamaged pieces to land back on the board, in legal positions. There is a lot of space inbetween the planets, however.

In any case, having a huge gravity spike (or a flyby rogue planet/twin planet come in and get captured) interact with the solar system, could result in moving Mars (your only real hope of putting another planet in the habitable zone) closer. But, moving planets into the habitable zone is not directly related to destroying/removing Earth.

Also, define 'livable'. Mars is livable right now, with the right technology. If you mean shirt-sleeves, growing things outside, breathing the atmosphere... No. See the habitability canonical question for all of the things that need to happen (and the lengthy timescales involved).

I rather like the idea of a rogue planet capture. It's wildly improbable, but you could have a planet that used to be formatted by life get captured in the habitable zone, and warm up. Comes pre-rusted, pre-oxgenated, and scoured of life by billions of years of frozen temperatures. Well, excluding the deep oceans. Assuming the planet still has internal warmth (which you'd want if you want to put life on it), means the ocean deeps (and some subterranean stuff) will still have life. And maybe some quite nasty stuff.

Perhaps you might be able to have very powerful aliens bring an anti-matter weapon to bear on the Earth, if you're really keen on removing the planet.

Answer 3

You could run an $N$-body simulation to find out. There is a free code that is very easy to use (I happen to maintain it): https://github.com/hannorein/rebound