Like what is the ultimate fate of the voyager probes and others on escape trajectories? My understanding is that space is far too sparse for these things to ever hit anything by coincidence, so their eventual fate is probably to be ejected out of the galaxy at some point.

They are then unlikely to be moving fast enough to actually cross intergalactic distances quickly enough for the expansion of space to not outpace the distance covered, leaving them in this void forever.

How long would they be recognizable as technological objects before the eons worth of stray hydrogen atoms erode everything away?

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[–] HelluvaBottomCarter@hexbear.net 8 points 4 days ago (1 children)

Newton's first law, they will move until something stops them. Like you said, space is very empty and they likely won't ever collide with asteroids or anything. If they get close enough to a planet, which is unlikely, they could fall into orbit and then that orbit will decay until they crash.

To even exit our solar system is a task. They still haven't left and it's been decades. Every now and then you'll hear news about how they're leaving or have left, but they're still technically in our system and will be for some time. Humans will probably be dead before they even leave the influence of our solar system.

Once they reach interstellar (between solar systems) space, they will just keep going, probably never reaching another galaxy. Voyager has like 721 kilograms of mass. If you took the average atomic weight of the materials its made of, and supposed it lost some amount of atoms per day due to microscopic collisions, you can ballpark the time until it turns into dust. Without doing the math, I bet it would be just a hunk of metal before even getting one lightyear away from our solar system.

[–] Xavienth@lemmygrad.ml 4 points 4 days ago

It may seem like the Voyager probes are declared to have reached interstellar space every now and then because there are different boundaries they had to pass through. Of note, there's the termination shock boundary, and there's also the heliopause. There's also two probes, so you'll hear twice as many declarations.

Really, though, they both are in interstellar space. They are out of the heliopause and are receiving an increase in cosmic rays indicative of being in interstellar space. Voyager 2 also has the capability to measure solar wind, and its measurements dropped around the same time cosmic rays increased. Voyager 1 entered interstellar space in 2012 and 2 in 2018.

Source

For your viewing pleasure, here's a graph of cosmic rays over time for both probes, and a distance scale is provided at the top for reference.