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Comment by cyberferret | Hacker News Reader

As 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?

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If you do this every day for millions of years, it's reasonable to expect a hit at some point.

Plates a few suburbs away don't exert massive gravitational pulls on their surrounding.

But 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...

Currently, 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.

I 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?

That just means that when the Tesla returns to the same point in its orbit, it will pass a few hundred miles above Earth's orbit (where the final burn was performed) instead of directly intersecting Earth's orbit.

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.

The point was made in the paper - since the Tesla was launched from Earth, its orbit has its closest approach to the Sun very close to the Earth's orbit, and this increases the chance of it being affected by Earth's gravity. This is because for part of its orbit, the Tesla will be effectively travelling along approximately the same path as Earth, just a bit faster. This means that it will approach Earth approximately one in every ten orbits. Hence the first interaction in 2091.

After a few interactions, the orbit becomes more funky, and interactions decrease in frequency.

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