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?
Interstellar space is so empty that it's not going to experience significant erosion from micrometeorites even over geological significant lengths of time. The interface points between dissimilar materials can be a source of corrosion, so certain portions of the structure will degrade in the relative short term. I don't know exactly what techniques and materials are used to attach the various parts of the structure, so I could imagine that galvanic corrosion would eventually cause the various booms to collapse and it to turn into a jumble of equipment that is just kind of flying through space. But there's no particular reason that it won't remain a recognizable artificial object billions of years from now - if there's no mechanism for an object to degrade, it just kind of continues existing. Take for example fossils such stromatolites, which are billions of years old, but still recognizable for what they are when examined by intelligent beings.
Will the golden record last a million years? Certainly. A billion? Probably, but there might be some process or environmental factor we don't yet know about that will cause it to degrade. A trillion? That's an awful long time, it seems like a bad bet to make... but it's not out of the realm of possibility.
Hitting an object straight on is certainly unlikely, I'm not so sure about getting caught in a gravity well and becoming a satellite. I imagine the escape velocity of the milky way on the whole would have something to say about it actually leaving, too.
It's not moving fast enough to leave the galaxy: https://www.tiktok.com/t/ZP8FDGo85/
Not sure how long it would take to erode away, but it's probably on the scale of billions of years. There's really nothing out there.
Over millions to tens of millions of years they'll be gradually eroded by cosmic ray spallation. They don't have the velocity to escape the galaxy so they'll kind of continue as they are, free drifting through space like everything else.
I was considering that there's probably a defined amount of time that would pass where we have a 99% chance the thing gets kicked out of the galaxy by gravitational interactions, either zipping too close to a black hole or the result of the galaxy itself being disrupted in mergers.
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.
Well, fuck, I hadn't ever thought of that.
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.
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.
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.
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This question caused me do some tangential navel gazing. The video mentions an escape velocity of 550km/s to leave the Milky way. According to some random stack exchange reply relative to Earth you will only need 317 km/s ∆v (because Earth is already orbiting around the galaxy at around 220 km/s).
I wonder how big such a rocket would be.
Best way to leave the milky way is probably to slingshot around a black hole. Stars get ejected from galaxies all the time like this
You don't have to be Ben Browder and surrounded by muppets, but it helps
Parker Solar Probe got up to a speed of 190 km/s during its mission by doing 7 gravity assists using Venus, which is like 10x faster than Voyager 1's speed - so like cosecantphi said - it is easier to just plan a trajectory that utilizes the gravity of some large object in the path of your destination rather than relying on pure thrust/a large rocket.Important to note that Parker Solar Probe has this speed extremely deep within the Sun's gravity well, whereas probes exiting the solar system just climbed out entirely.
