10 ms·
The random walk of cars and their collision probabilities with planets
- userbinator 9y agoBy running a large ensemble of simulations with slightly perturbed initial conditions, we estimate the probability of a collision with Earth and Venus over the next one million years to be 6% and 2.5%, respectively More fortunately, even if it were to "collide", it would likely burn up in the atmosphere like the majority of other, even very large[1], objects that reenter. [1] https://en.wikipedia.org/wiki/Mir#Final_days_and_deorbit https://en.wikipedia.org/wiki/Mir#Final_days_and_deorbit
- pavel_lishin 9y ago"Free Tacos for Everyone in the Solar System if Mir hits our Target on Venus!"
- eterm 9y agoReference for reference: http://news.bbc.co.uk/1/hi/world/americas/1231447.stm http://news.bbc.co.uk/1/hi/world/americas/1231447.stm
- jcims 9y agoParticularly since there is a potential that it would enter earth's atmosphere at 2-3x the orbital velocity of Mir.
- dsacco 9y agoHah. This is cool. 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 :)
- TeMPOraL 9y agoThere is one in ACKNOWLEDGEMENTS section: > This research has been supported by the NSERC Discovery Grant RGPIN-2014-04553.
- manaskarekar 9y agoVery cool, looks like this partially answers my curiosity https://news.ycombinator.com/item?id=16324894 https://news.ycombinator.com/item?id=16324894. It'll be fun to read papers about other projected fates of the various aspects of the Tesla.
- mirimir 9y agoI'm wondering about the fate of the paint, plastic, rubber and leather. https://www.autoblog.com/2018/02/07/tesla-roadster-starman-space-radiation-elon-musk/ https://www.autoblog.com/2018/02/07/tesla-roadster-starman-s...
- jkh1 9y agoAs if there was not enough junk in space already.
- ars 9y agoThere's junk in low earth orbit. But this object is in solar orbit. There's very little junk there. There's very little anything there.
- TheRealPomax 9y agoVery little junk, but _loads of stuff_ in solar orbit in the form of the asteroid belt, the jupiter greeks/trojans and the hildas, the kuyper belt, and the oort cloud. There is so much there.
- Sharlin 9y agoFor extremely low values of ”so much”.
- kybernetikos 9y agoMaybe, but on the other hand, I expect you've hardly ever used 'so much' to refer to more - since a small fraction of that 'so much' includes Earth and everything on it. As with everything, it depends on what your comparisons are to.
- deleted 9y ago[deleted]
- ars 9y agoIt's hard to really wrap your mind how BIG it is 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.
- TheRealPomax 9y ago
- fsiefken 9y ago2 questions: > 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?
- ukulele 9y agoTerrestrial planets usually means inner 4 in our solar system, and "earthlike" elsewhere
- boxed 9y agoRe. dynamic lifetime: you are right that there are many rocks. You underestimate the vastness of space though. Collisions are extremely rare and the Tesla is pretty small.
- PeterisP 9y agoWhat collisions? The whole point of this article is that the most likely rock to hit Tesla is the Earth. Space is very, very, very empty; all the (many) rocks out there are scattered in extremely huge amounts of empty space. 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.
- kijin 9y agoIt's also worth noting that Earth is more massive than Mercury, Venus, Mars, the Moon, and the asteroid belt combined. 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.
- xixixao 9y agoIt’s pretty incredible to imagine that after most of the monuments man has built for man have vanished, Elon’s Tesla might still be orbiting the Sun. Feels implausible.
- lttlrck 9y agoVoyager 1 & 2 are the trailblazers here and the chances of them colliding with anything are markedly lower I would assume.
- avian 9y agoPioneer 10 and 11 probes left the solar system as well. 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.
- cryptoz 9y agoI sure hope that's not the way things go. Eventually humanity will be extinct, but long before that I'd image we'd build far more out in space than we have on Earth.
- taneq 9y agoWithin a couple of hundred years (maybe even much less) someone's going to go and collect it for bragging rights and/or as a trophy. See if they don't.
- fyfy18 9y agoIf SpaceX ever gets into asteroid mining, it’ll be good practice to return it to earth.
- lovemenot 9y ago>> See if they don't. Hope to live long enough to see you proved wrong.
- noonespecial 9y agoIt will be designated a solar system historical site and be strictly off limits. You can't exactly sneak up on something in space...
- antognini 9y agoHanno Rein and Daniel Tamayo are pretty legit dynamicists. For anyone interested in doing calculations like these themselves, they've been working on this amazing N-body library called Rebound: https://github.com/hannorein/rebound https://github.com/hannorein/rebound One of my all-time favorite figures is Fig. 1 of this paper of theirs describing one of the integrators used in Rebound: https://arxiv.org/abs/1704.07715 https://arxiv.org/abs/1704.07715
- simonbyrne 9y agoThanks for the link, that paper was a great read: clever idea, and very well written.
- cyberferret 9y agoAs high as 6%? In the total vastness of space, 6 in 100 seems like an incredibly high chance that the rocket payload will hit either Earth or Venus... It's a bit like me pulling out a rifle and firing into the air, hoping to hit a specific dinner plate in a back yard two suburbs away on a windy day, isn't it?
- SeoxyS 9y agoPlates a few suburbs away don't exert massive gravitational pulls on their surrounding.
- cyberferret 9y agoBut doesn't gravitational pull mainly deflect objects travelling at high velocity? Hence their use to accelerate spacecraft into different trajectories? If we looked at the 'indentations on a rubber mat' model of gravitational influence, the object would still have to be aimed almost directly at the planet in order to hit it rather than bend around it? 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...
- kijin 9y agoCurrently, the Tesla is aimed almost directly away from Earth. After all, it was launched from Earth! 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.
- cyberferret 9y agoI hope that other members more in the know can clarify, but I thought that the launch into deeper space was done as a 2 stage thing - first, they got the car up into earth orbit, THEN they did a second burn to break orbit. i.e. the second burn was done while the vehicle was moving tangential to the Earth, and not radially away from it?
- snakeboy 9y ago> In our numerical model, we do not integrate the orbit of the Moon and instead use a single particle with the combined mass of the Earth and the Moon. 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?
- sudhirj 9y agoOnly the initial launch has the car near the earth and moon, but the calculations are already factoring in a range of starting points - I’d assume the moon’s effects are contained in that range. 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.
- Someone 9y agoThe mass of the moon is only about 1.2% of that of earth. 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?)
- gmiller123456 9y agoYes, for things "far" away from the Earth. They said they started their simulation on Feb 10, the launch was on Feb 6, to the roadster was far enough away at that time to ignore the Earth and Moon being separate. I didn't see where they mentioned it in their paper, but they likely started with either published location/velocity data, or used observations to compute its position and velocity for the start on the 10th.