One of my all-time favorite figures is Fig. 1 of this paper of theirs describing one of the integrators used in Rebound:
More fortunately, even if it were to "collide", it would likely burn up in the atmosphere like the majority of other, even very large, objects that reenter.
> The repeated encounters lead to a random walk that eventually causes close encounters with other terrestrial planets and the Sun.
What are terrestrial planets? I thought there was only one terrestrial planet; earth. Or is meant 'earth like' planets, specifically Venus, Mars and Earth?
> dynamical lifetime of the Tesla to be a few tens of millions of years
What is the dynamical lifetime? I'd think that with all the rocks out there the Tesla will get some dents from collisions. So many dents that I think in a million years it'll be toast. How does this square with a dynamical lifetime of tens of millions of years?
Terrestrial planets have a solid planetary surface, making them substantially different from the larger giant planets, which are composed mostly of some combination of hydrogen, helium, and water existing in various physical states.
Even in a dense asteroid belt, almost every path encounters zero rocks; and the orbit of that Tesla is not in asteroid belts but in interplanetary space that's quite "clean".
Tesla would be expected to get some abrasion / "wear&tear" from hitting individual atoms and tiny particles of space dust; over a million of years that would likely accumulate to a major change. But it's not likely to hit a rock of "dent-making" size before it gets sucked in by some major planet.
Since the Tesla doesn't go anywhere near Jupiter's orbit, if it gets sucked in by anything at all, it's likely to be Earth.
But indeed, Mars has only about 1/10 the mass of Earth! And Mercury is about half of that.
It also has the highest density of all the planets, thanks to the iron and nickel in the core. Earth is so dense that its surface gravity is higher than that of Saturn and Uranus (for a suitable definition of "surface" for the gas giants) despite the fact that the latter are much more massive as a whole.
We should make note of these facts and use them to burn the aliens if we ever come to an interplanetary rap battle :)
Is that a standard assumption for this kind of model? For such a chaotic simulation, would it not be very important to approximate the effects of the Earth and moon very precisely? Especially since these bodies would have such dominating effects early on?
After it moves away from the earth the distance ought to be negligible, although even if they do reduce the earth moon to a single point I don’t know if they model a wobble.
Also, “early on” earth is much, much closer than the moon. The gravitational pull of the sun is >100 times as large as that of the moon there, and both are minute compared to that of earth (you don’t feel much lighter or jump higher when the sun or the moon are overhead, do you?)
It'll be fun to read papers about other projected fates of the various aspects of the Tesla.
I think it’s also likely that all the stuff left on the moon might be longer lived than a car shooting randomly around the solar system.
Imagine SpaceX selling tickets to rendezvous with the car, put you in a spacesuit, and sit next to Starman.
What a photo opportunity!
Hope to live long enough to see you proved wrong.
But I guess that comes down to the velocity of the object in question, and after repeated trajectory adjustments due to gravitational pull, it could quite conceivably end up aiming directly at a massive body in space that exerted the pull in the first place...
On the other side of the orbit, that becomes almost directly at Earth.
Go round and round a few million times, and Earth might actually be at a point in the orbit where it can exert a significant gravitational pull on the passing Tesla.
After a few interactions, the orbit becomes more funky, and interactions decrease in frequency.
The difference is virtually meaningless compared to orbital perturbations from other sources. Either way, it's close enough for Earth to affect the Tesla's orbit if it were at the right place at the right time.
I’ve become so used to reading papers with a footnote that states something about an NSF grant being used to support the research that I was initially surprised when I didn’t see it here. Then I realized what I was reading and chuckled :)
> This research has been supported by the NSERC Discovery Grant RGPIN-2014-04553.
There is so much there.
Those things you mention? They take up so little space they wouldn't even count if not for the fact there's nothing else.
Space is REALLY big, and REALLY empty.
As with everything, it depends on what your comparisons are to.
I like to use this comparison: a single cell you shed from your skin pollutes the Earth more than the Roadster pollutes the Solar System.
(convert erythrocyte | diameter to meters)×(convert diameter of Neptune's orbit to kilometers)/(convert Earth | average radius to kilometers) = 11 meters
edit: Of course you could argue with this calculation in all kind of ways - widths vs volume vs mass ... but I think for such a silly analogy this is good enough to say: It is not totally unreasonable.