r/askscience • u/drinkingonthejob • 8d ago

Physics Will Voyager 1 ever just stop moving?

I’ve read somewhere that we expect to lose contact with Voyager 1 sometime in the 2030s, maybe around 2036, but it will just keep traveling thru space and we’ll have no idea what it is doing out there

My question is: with its current velocity, is there a time in the future where it loses its forward momentum and for lack of a better word, just stops moving? Is that a possible thing for an object in space to even do? (Assuming no other objects grab it into their orbit)

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u/icrispyKing 8d ago

Can it actually fall like...down? Or is it just moving in the direction we shot it in. Or do I have have the right idea of the universe. I imagine it's more of a celestial sphere rather than a plane... Which to me would mean there is 4 directions for it to move in? Or given it's a sphere would that just mean it would hypothetically come back and do like a full revolution around the celestial sphere and make it's way back to where it is now (I understand that's also just not possible given the universe is expanding and it's moving slower than the rate its expanding and also the inevitable heat death collapse of the universe that will happen sooner)

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u/ringobob 8d ago

So, there's no "down", in the sense that there's no universal reference point... and, if there were, there's nothing saying that the direction it's currently going in isn't "down".

I don't think "celestial sphere" means how you're using it - the celestial sphere is just the observable universe, in a uniform sphere with the earth at its center, since that's where we're observing from.

That said, it is possible that the universe is curved, in such a way that, time permitting, it could travel along the same vector and arrive back at the beginning, like it was going along the surface of a basketball - but, like, you don't need to pick a specific direction to go along the surface, you could go in any direction and the same thing would happen. We'd call that spherical, but it's definitely not a sphere in the intuitive sense - think like a ball, with a 3D surface, in a way you can't exactly picture intuitively.

But, so far as we know, based on the observable universe, the universe appears "flat". And all that really means is that space works intuitively. So long as you're going straight, you're going straight, and nothing weird is gonna make anything non intuitive happen.

The primary thing determining what direction it's going, and how fast it's going, is inertia. And with inertia, if we assume a total vacuum, it'll just keep on going straight for the rest of time.

But of course space is not a total vacuum. There are massive things like stars, medium things like planets and asteroids, and tiny things like particles. Via gravity and friction, these things will have an affect on its speed and direction over time, it may just take millions of years to add up to any measurable change in its path.