[hdgvhicv]

Based on the interstellar density it will take a billion years to ablate just a millimetre off its outer layer.

The chance of impacting anything larger than that is internal, same as an encounter with another star. In 40,000 years it will get to within 1.6 light years from a star, that’s such an unimaginable distance it’s irrelevant.

In 100 million to 1 billion years you may not be able to recover audio from the golden record, but until that point they will be lasting remnants of a civilisation long gone, and never be encountered.

Voyagers will only impact a few thousand kilograms of material before all stars die out in 10^14 years, it will still be an object after the final stars fade.

The biggest risk to voyager now is if proton decay is a thing, or if a civilisation deliberately seeks it out, which seems very unlikely given how many natural lumps of iron int he 1 ton range flying through interstellar space.

[Retric]

“In 40,000 years it will get to within 1.6 light years from a star, that’s such an unimaginable distance it’s irrelevant.”

On most human timescales that’s a long time, but here it’s only 0.004% of a billion years and in general stars are ~5 light years between closest stars in our neighborhood. If you assume zero significant impacts means it’s around in 100+ billion years there will be many vastly closer passes than 1.6 lightyears. It’s the kind of thing you really need to simulate because gravity plays a larger role the closer voyager gets to another star.

[hdgvhicv]

Not at light years. How many non-binary stars do we see colliding with other stars. They don’t. Even when andromeda runs into the Milky Way it won’t result in stars colliding. The chance of the sun colliding with another sun is somewhere in the 10^30 range.

Voyager may end up in a solar system briefly as a high speed extra solar object like Oumuamua, but the chance of it being close enough to suffer any physical affect would be small - think how small a target that would be and how rare stars are. To get within 1 light day would mean passing 100,000 stars within one light year. To get down to earth distance is something like 4 billion passes within a 1 light year distance.

Now sure predicting the future beyond say 100 billion years is tricky, and not something you could simulate, but for all intents and purposes the voyagers will continue long after Earth has died. It (and other craft on escape trajectories like new horizons and pioneers) will be the last remnants of human civilisation

[Retric]

Stars hitting stars isn’t the metric a baseball sized object clearly counts as a meaningful collision at these speeds. Add up all objects in terms of 2d cross sections and it’s the small stuff we’re going to care about, but getting near stars matters because from what we can tell there’s so much more small stuff near stars. The Oort Cloud sits 0.03 to 0.08 light years from the sun etc. https://en.wikipedia.org/wiki/Oort_cloud ~5 earth masses in vastly smaller objects is a lot of targets. (I recalled an earlier and far larger estimate but it’s still a lot of material.)

Ignoring gravity may be fine at 1.6 light years but a closer approach to even just say 2 light months means spending thousands of years much closer to the star which would matter here. So simple extrapolation based on random distribution of nearest approaches like you just proposed with that 100,000 star calculation is heavily biased in the wrong direction.