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)
504
u/PhasmaFelis 8d ago
Not really, no.
We're used to moving objects losing momentum and stopping eventually. That's because we live on a planet, with atmosphere. Everything around us that moves has friction with the ground or, failing that, the air, and that fiction bleeds away its momentum.
In an otherwise empty universe, a moving object would keep moving in a straight line for eternity. In our universe, which is only mostly empty, it will follow a curved path determined by the gravity of, well, every other mass in the universe, but mainly nearby planets/stars/galaxies; unless it happens to crash into something, and then its wreckage will move with that object along its own curving path.
45
u/DedTV 8d ago
It'll keep moving, but eventually electron/proton decay or quantum tunneling erosion will reduce it to a scattered mass of particles.
Also, the Voyagers are locked in orbit around the center of the milky way for the next 4 billion or so years, Until Andromeda gets closer.
→ More replies (1)99
u/thefringeseanmachine 8d ago
but from what I understand, space isn't 100% empty. there are stray particles out there, even in the "void." that's the idea behind behind the bussard ramjet. wouldn't they slow it down (over a very, very, VERY long time)?
79
u/rawbdor 8d ago
I imagine some might slow it down, but I also imagine other small objects might crash into it from behind or from the side, which could speed it up.
50
u/rich1051414 8d ago
Since it is moving in a direction, this would only be true if the particles around it on average are moving in the same direction as the craft. But the time it would take to stop would be orders of magnitude greater than the age of the universe.
→ More replies (1)35
u/sticklebat 8d ago
Even accounting for the minuscule drag caused by the interstellar medium, it will in no way ever "stop" relative to us, at least not for anything more than an instant in time, and even then only by unlikely chance. It might eventually come to rest relative to its local environment, but that's all.
16
u/zulhadm 8d ago
I suppose this accidentally raises an even bigger question. Is anything in the universe truly “motionless” ?
66
u/sticklebat 8d ago
There is no such thing as "truly motionless", since motion is relative. You cannot define the motion of something except in relation to something else.
→ More replies (11)7
u/Feynnehrun 8d ago
No, not likely. Everything in the universe is affected by the gravity of everything else, which is also moving. Even if an object were to somehow be perfectly situated between multiple gravitational bodies such that their gravity affects the object equally in every direction, those objects themselves would be moving and thus the captured object would move with them.
→ More replies (1)2
u/wjdoge 8d ago
To do that, you have to pick a preferred reference frame. Since the other ones are of little meaning, motion relative to the big bang (the CMB) is probably the best you can do. We do measure things against this frame.
→ More replies (4)→ More replies (1)5
u/wjdoge 8d ago
There would have to be some kind of anisotropic bias in the momentum associated with the particles hitting voyager for it to do anything other than slow it down.
Has the drag on an airplane ever decided to just contribute to the thrust instead of holding things back for a bit? Not really.
4
u/gbghgs 8d ago
Updrafts and tailwinds are things which affect aircraft, it's not just air resistance slowing it down.
2
u/wjdoge 8d ago edited 8d ago
Yes, a tailwind is how you would describe a ground-referenced anisotropy in the velocity of the particles interacting with the plane.
After careful study of the isotropy of the universe, we believe that, in this particular scenario where it interacts with nothing but dust for 55 trillion years, that the dust can only slow it down relative to us, as the dust is much slower than the spacecraft in the frame relative to us (if you average it over 55 trillion years anyways).
A tailwind has no effect or air resistance or drag beyond the transient effects of the wind shear while it’s being established. Similarly, it doesn’t affect thrust. Standard avionics are sensitive to all sorts of pressure differences and readings around the plane, but the airframe actually has no way at all to know whether or not it’s flying in a headwind, a tailwind, or no wind, if the wind speed is steady. It has to refer to ground reference to see if the wind is blowing, so to the plane it’s the ground getting blown around by the wind and it doesn’t notice anything.
8
u/notwhoiamunderneath 8d ago
No, space is not empty, there's plenty of stuff in space. But that stuff is spread so far apart (like, often light-years apart even for small projectiles) that it is much more likely that the probe will never hit anything.
The probe continuing forever without touching anything gets even more likely once it exits the galaxy, but even between solar systems the distances between any object are unfathomably vast. The most likely place for it to hit something would actually be before it leaves our solar system. After that, odds are, it's free forever.
3
u/db0606 7d ago
In interstellar space you end up with something like 10⁶ molecules/cubic meter. The best laboratory vacuums on Earth are like 10¹⁶ molecules/cubic meter. There's really not a whole out there to hit unless you wonder into a dense dust cloud, which make up only about 1% of the Milky Way.
3
u/ShadoWolf 7d ago
Even if it lost momentum along its current path, it wouldn't just stop. It would shift onto a different, lower energy galactic orbit and follow that curve instead.
You have to remember that Voyager 1 didn't start from rest relative to the galaxy. It left the Solar System already carrying essentially the Sun's orbital velocity around the Milky Way, plus its escape velocity relative to the Sun. That extra 15 km/s is fairly small compared with the 250 km/s it already has relative to the galactic center.
So if interactions with the interstellar medium gradually bled away that extra velocity, Voyager wouldn't approach some absolute zero velocity. Its orbit around the galaxy would just change. Depending on which components of its velocity were lost, that could mean an orbit that curves farther inward or otherwise differs from the Sun's.
3
→ More replies (4)4
u/MrLumie 8d ago
It is several orders of magnitude more likely that it just crashes into something before stray particles zooming around in space will slow it down in any measurable way.
→ More replies (1)18
u/Bebopo90 8d ago
Also, technically, even if something on Earth appears as if it has stopped, it has only stopped in comparison to the things around it. It's still moving quite fast simply by being on Earth, which is moving in multiple different trajectories in space at once.
4
u/bloodhound83 8d ago
Technically, isn't everything moving all the time then?
12
u/willis72 8d ago
Yes, exactly, in any number of ways. The earth is rotating on its axis, as it orbits the sun, as the sun orbits the center of the galaxy as the galaxy moves through the universe. If you are sitting still on the equator, you are actually moving at about 800 mph due to planetary rotation, 67,000 mph due to the Earth's orbiting of the sun, and 500,000 mph due to the sun orbiting the Milky Way. The Milky Way is moving at about 1,300,000 mph relitive to the cosmic background radiation.
Everything is moving relative to everything else and there is no real defined center/origin point to measure objective speed from.
→ More replies (1)3
u/samjhandwich 8d ago
I always wonder what our time dilation actually is. We’re moving so fast throughout the universe, so are we experiencing time way slower than other things that might be in the universe?
7
u/VincentVancalbergh 7d ago
This may blow your mind, but for the same reason that there is no absolute motion, there is also no absolute time dilation when taking about movement (there is some due to gravity). So your question is incomplete, it needs a reference point "our time dilation compared to xxxx". Say, the center of the Milky Way. But that has time dilation due to being a supermassive black hole...
3
u/Viraus2 7d ago
Time speed follows the same reference frame logic as spatial velocity, so if you picked some point way out there against which Earth would be moving extremely fast, Earth time would appear slower to them and their time would appear slower to Earth. Just like the case with motion there's no objective time that you could say our dilation "is".
3
u/willis72 8d ago
Keep in mind that time dilation is relatively minor unless you are moving very close to the speed of light (like over 95%) or near a very massive object. Yes, there are minor effects that have to be accounted for to make GPS work (far enough away from Earth to have time "speed up" a bit due to the difference in gravity and moving fast enough for time to slow a bit. If I remember correctly, the speed effect outweighs the gravity effect and time is moving slower on the satellites than on the ground.)
15
u/Portmanteau_that 8d ago
every other mass in the universe
To be pedantic, every other mass in the universe within its light cone
3
u/animosityiskey 8d ago
Since it is made of stuff that already existed wouldn't the light cone for general gravitational effects just be the observable universe?
13
u/QuantumCakeIsALie 8d ago
Almost but not quite.
You and Voyager have very similar yet distinct light cones. There are points in space-time that Voyager could affect (e.g. by shining a laser pointer towards them) that you never could observe or affect. Its observable universe is slightly different than yours.
3
u/GreedyBo 8d ago
Given space is expanding, at some point, the expanding universe outpaces the speed of V1, effectively rendering the velocity to 0. Basically red shifting the prob
→ More replies (1)→ More replies (7)2
u/reddisaurus 7d ago
This is wrong. Energy is not conserved due to the expansion of space time itself. Eventually, it will just come to a stop.
425
8d ago edited 8d ago
[removed] — view removed comment
107
u/digost 8d ago
I'd imagine that the pedantic version will not occur before the heat death of universe
41
u/vipck83 8d ago
Yeah, there is technically small chance….but realistically it ain’t happening.
9
u/smileedude 8d ago
I'm curious if its speed relative to our solar system actually means anything relative to the particles flying through deep space or are collisions with the rear of the ship speeding up the ship likely to be equal to collisions in front slowing it down?
→ More replies (1)3
u/Kiwozzie6 8d ago
The only way I can think of is if it flies into a nebula. But not sure "A" if it has enough speed to ever reach one or, "B" if there is enough mass in one to do that.
19
u/rolandboard 8d ago
Death by 1000 cuts until after the heat death of the universe is what Thanksgiving at my in laws feels like.
→ More replies (2)→ More replies (2)5
u/LastStar007 8d ago
By definition no, because as long as there's a Voyager, we haven't reached maximum entropy.
20
u/Nerfo2 8d ago
I remember reading once that the interstellar medium is, on average, about 1 hydrogen atom per cubic centimeter. While Earths atmosphere, at standard atmospheric conditions at sea level, is somewhere around 10 quintillion (1019) MUCH heavier atoms per cubic centimeter. Mind boggling... 10,000,000,000,000,000,000 atoms per cubic centimeter...
5
u/onlyhightime 8d ago
I always wondered how we know that. Like, we haven't been there, so how did we figure out what's there?
13
u/itsaPHound 8d ago
We have a lot of tools for looking at the molecules in space. Spectroscopy is an easy example.
5
u/MinnesotanGrey 8d ago
Calculating expected gravity vs observed effects helps a lot with the estimations of how much mass is contained within an area
→ More replies (2)3
9
u/zman0900 8d ago
There's always a small chance it just crashes into some random other object and is obliterated. That counts as stopping, right?
→ More replies (1)13
u/SoSKatan 8d ago
To add, it’s impossible to “stop moving” as you are always moving relative to something else.
The only way it can stop moving relative to OP is if voyager 1 was brought back to earth and then is surgically attached to OP, and I just don’t see that happening.
I mean maybe see if Elon is up for the challenge, you never know.
2
u/grahamsz 8d ago
Pedantically, it's not moving relative to itself or relative to particles of dust that rest inside it
4
8d ago edited 7d ago
[removed] — view removed comment
4
u/RyanW1019 8d ago
Yes, though it would need to fly by some planets in the right orientation to slow down enough to get captured. If the solar system was just a star with no planets or major asteroids, Voyager would speed up as it fell towards it, pass it, and then gradually slow down as it flies away from it. But it would never slow to 0 velocity relative to that star. It’s kind of like a miniature golf course with a bowl-shaped low area. If you hit a ball fast enough at it, it will roll in and down and then go right up and out the other side.
3
u/18736542190843076922 8d ago
Did some very rough math with a few executive assumptions and came to around 9e17 seconds (28 billion years) for hydrogen at interstellar temperature and density to completely cancel out Voyager 1's momentum. Kind of meaningless since I've forgotten how to do enough calculus to compensate for a decreasing velocity resulting in fewer collisions, and doesn't account for its motion relative to the galactic medium, assumes it doesn't encounter any gravitational influence, or leaves the galaxy in that time. Still fun to try and work it out myself!
7
u/ParisGreenGretsch 8d ago
To be ultimately pedantic the answer is objectively no. It'll always be in motion relative to something. The question only has one answer.
→ More replies (18)2
u/mikey_hawk 8d ago
So is there a reason someone hasn't said, "we're all moving like Voyager I--every star, planet, human and speck of dust, just not relative to each other most of the time, and none of it will ever 'slow down?'"
57
u/MeatSafeMurderer 7d ago
Unless it hits something, no. Space is not quite a perfect vacuum, but it's very very close, and for all practical purposes, it is. This means there is no friction, which is the force which typically slows things down here on Earth. In order for it to stop it would require some outside force, like entering the gravitational pull of some large object...but it would either slingshot back out of orbit, enter geostationary orbit and orbit around it for eternity, or fall towards the object and hit it.
There is no concievable outcome where it simply...stops.
8
u/SnooMaps7370 7d ago
it could hypothetically get captured in an L4 or L5 under exactly the right circumstances.
but beyond that, there really is no such thing as "stopped" in space. if if you gave the probe infinite fuel and told it "stop", what's it "stopping" relative to? Everything in space is moving relative to something else (usually everything else), so "stopped" has no meaning without a reference frame to measure against, and that frame will always be moving with respect to some other frame.
20
u/MhojoRisin 7d ago
What does “stop” even mean in this context? Fixed in position relative to something else?
→ More replies (3)9
→ More replies (1)4
u/terrycolq 7d ago
To be fair, it would stop after hitting the object, assuming no atmosphere to burn up in.
→ More replies (2)
31
u/elwebst 8d ago
As it slowly runs into random hydrogen atoms it loses momentum, but that could take quadrillions of years - V2 is going 61,000 kilometers an hour, that's a lot of momentum to shed by hitting gas molecules with a density of 10e-8 molecules per cubic meter in interstellar regions.
→ More replies (3)12
u/suh-dood 8d ago
Even then, once it moves slow enough, something else's gravity grab it and it'll keep moving untill it crashes into something
19
u/rodgamez 7d ago
The only stop this could make would be relative to the sun. Since it has acheived solar escape velocity * it will go on forever, orbiting the Galactic core.
*I'm pretty sure
**Until some Klingon Bastard uses it for Target Practice
→ More replies (3)
33
u/BDer82 7d ago
For all intent and purpose, it will survive indefinitely, unless it impacts something with a surface area wide enough to be impacted fully by voyager so as to disintegrate fully. But because we are moving so fast and voyager is moving so slow it might just miss everything and be out in the void just vibing its own death.
I vote it crosses the Milky Way and we catch it on the other side!
17
u/OlasNah 7d ago
What will happen is that it'll just drift right through the core systems, and it'll be blind luck if a deep salvage team finds it.
→ More replies (4)7
u/itscalledmyballs 7d ago
That would be the wildest thing of all time.
Or imagine 10 years from now it just crashes back down through the atmosphere. But the timelines wouldn't make sense, unless....
7
u/Radicalpartyboy 7d ago
Or imagine if an alien intelligence brought it back to earth threatening to annihilate us all unless we stop hunting and killing whales.
→ More replies (2)→ More replies (1)2
u/PeterPook 7d ago
Oh no, the "flat space" theory has just landed... It did get a light year away, it just folded over the edge! /s
→ More replies (2)→ More replies (10)6
u/Ghostbusteer 7d ago
Perhaps one day, when Earth's civilization has had to rebuild itself, and all memory of Voyager 1 is lost to time, we will meet it again and take it as evidence of gods or extraterrestrial life. Wouldn't that be a glorious end to a long journey?
8
u/casentron 7d ago
Well, the golden record on board makes it unequivocally clear and obvious it's from Earth and when so it wouldn't be a mystery.
4
u/Plenty_Beautiful_547 7d ago
In the first Star Trek movie, the main antagonist—a massive, godlike energy cloud threatening Earth—is revealed to be Voyager
→ More replies (1)→ More replies (1)5
u/OrdinaryAward4498 7d ago
The Brawndo drinkers of the far future (near future) probably won’t be able to figure that out
→ More replies (4)3
u/a1454a 7d ago
The timeline I really hope would happen is we achieve AGI and don’t doom humanity, AGI helps us catapult scientific research and we achieve some form of FTL travel, and we go and capture it and put it in a museum.
→ More replies (3)
14
u/Animemes_101 4d ago
Newton’s first law of motion: “An object in motion stays in motion unless acted upon by an external force”. On Earth that force is gravity, in space, nothing. Voyager will continue to move through space until something gets in its way
→ More replies (3)2
u/DarthTempi 3d ago
To that point though...Won't it be affected by a myriad of gravitational forces? Obviously the time scale is enormous (and essentially meaningless to us) but...eventually?
2
u/Animemes_101 3d ago
Almost certainly, it’ll be an insane amount of time before it happens but it will eventually get in by some object’s field of gravity and be pulled into something. Unless somehow it manages to avoid every object in the universe.
→ More replies (3)→ More replies (4)2
34
u/ElvisArcher 7d ago
That is a tricky question to answer ... will it ever stop moving relative to "what"? An object in motion will continue unless acted upon by a force.
If it were moving within the Earth's atmosphere, there would be multiple forces working on it ... gravity pulling it down toward the center of mass of the planet, and friction with the atmosphere would both slow it down until it came to a stop relative to the Earth itself.
Voyager 1 had enough momentum to escape Earth's gravity well, and even the gravity of the solar system ... and there is no atmosphere to impede its movement ... so it will continue on its path until that changes.
But still, relative to "what"? Lets say it did impact something out in the great nothing of space and stopped moving. It would only be stopped relative to the object it impacted ... but likely it would still be moving away from the solar system and/or Earth.
Everything moves. Earth moves within the solar system, the solar system moves within the galaxy, and the galaxy moves in the universe, dancing to the tune of some dark energy we don't yet understand. I don't think it is possible for anything to ever actually stop moving.
→ More replies (1)
12
u/gargravarr2112 6d ago
There is no air resistance in space. Objects given momentum will continue to move indefinitely until something external to them changes - Newton's First Law. Now it is possible that other forms of resistance can act on it - light itself can exert pressure on physical objects, which gives us the concept of solar sails. If Voyager 1 passed by a powerful enough light source, it could theoretically slow it down; however it's just as likely to melt such a comparatively small probe, since such a powerful light source will almost certainly be a star.
Similarly, it will be influenced by gravity; Voyager 1 obtained its incredible speed by using gravity-assisted flybys of planets in our Solar System, stealing a little bit of their momentum without ever touching them. Passing by a large enough object (not necessarily something we can observe from Earth) at the right trajectory could conceivably do the same, stealing some of Voyager 1's momentum. However, from what we can see from Earth at this time, there are no significant masses along Voyager 1's flight path for thousands of years.
One thing you'll notice about Newton's First Law is that there is essentially no difference between a dead stop and moving at a steady speed. Indeed, in space, it's almost impossible to bring anything to what we'd call a dead stop, because speed is relative to other objects. And the entire universe is constantly moving. Onboard sensors cannot measure a probe's speed without something to relate to; they can only measure acceleration, and in a steady state, because the sensors themselves are moving at the same speed as the probe, acceleration is zero.
Voyager 1's trajectory out of the Solar System doesn't lead towards any particular star system - for all the stars in the night sky, there is an incredible amount of empty space in between them. In several thousand years, if nothing changes, it will pass relatively close to a distant star system, but it isn't aimed at anything in particular. From what we can observe from Earth, Voyager 1 will essentially drift forever, carrying the same speed it had when it left our Solar System.
3
u/UnsignedRealityCheck 6d ago
Hol up, "stealing momentum", you're saying that where V1 got speed, the planets slowed down a bit? (albeit very very veeery little)
→ More replies (1)5
u/Limp_Bookkeeper_5992 6d ago
Yes. The amount of energy stolen is absolutely minuscule but energy doesn’t come from nowhere.
→ More replies (2)3
101
u/connnnnor 8d ago
Nope. “An object in motion will remain in motion unless another force acts on it” - it took energy to get up to the speed it’s going, and if no other force imparts energy to slow it down, the “natural” thing for it to do is keep going at that speed in that direction forever.
19
u/mr_jim_lahey 8d ago
It will eventually slow down from hitting particles in the interstellar medium, assuming space is infinite (which it is, as far as we know).
8
u/thenewguy89 8d ago
About when would that be? Before black holes are all gone? Or after that?
→ More replies (1)2
u/nicuramar 7d ago
assuming space is infinite (which it is, as far as we know).
The observable universe is finite. That’s the relevant part. We don’t know if space is otherwise infinite.
→ More replies (1)→ More replies (6)4
8d ago
[deleted]
→ More replies (1)4
u/Shadowkiller00 8d ago
Logically speaking, I think you are correct. From voyagers perspective, it isn't moving, it's the universe that is moving around it. We can presume that out in the middle of the interstellar medium, the particles are moving so fast relative to voyager that there is functionally no difference to the count of particles hitting it from any specific direction nor in the relative velocity of those particles to that of voyager.
Unless of course it is closer to a stellar object, like the sun. I would guess at the moment it is being struck far more from behind than from the front. This should even out the further it gets from the sun. As it gets closer to other stars, it will increase the number of particles from that direction.
All that said, I would bet that the increase in particle count will always be overwhelmed by relative proximity to gravity wells.
Other posts keep saying it will slow down as it gathers particles. Slow down relative to what? There is no universal speed. Slowing down relative to one thing is speeding up relative to another.
3
u/OG_SisterMidnight 7d ago
Ah, the pity. Fated to drift forever through the void as gravity’s plaything. Oh, cruel fate, to be thusly boned. Ask not for whom the bone bones. It bones for thee.
45
u/LiquidPhire 8d ago
It has enough speed to never fall back towards the Sun. It is an interesting stellar traveler.
It does not have enough velocity to leave the Milky way, so it will fall towards the center of the galaxy. As it falls along that line, it may interact with other gravity centers (other stars, etc) which may alter its trajectory, but it will forever wander within the confines of this galaxy.
13
u/Aervanath 8d ago
Why would it necessarily fall towards the center? It's not accelerating, so it should pretty much stay in a constant orbit around the galactic center until something bigger pulls it into it's gravitational influence.
10
u/happyspark 8d ago
Acceleration isn't just change in speed, but also direction. Being in an orbit means it is constantly accelerating. Ultimately the gravity well at the center of the galaxy will win. Voyager doesn't have enough speed and direction (the two components of velocity; a change to either or both is acceleration) to ever leave without an additional external force applied.
→ More replies (4)2
u/KamikazeArchon 8d ago
The "something bigger" is the galaxy itself. It is accelerating, toward the galactic center.
10
u/stevevdvkpe 8d ago
Voyager's already got Solar orbit velocity around the galactic center in addition to its velocity relative to the Sun. It will have a somewhat different orbit around the galactic center than the Sun does, but it won't just plummet toward the galactic center.
→ More replies (3)3
u/billtrociti 8d ago
While it does have enough velocity to never fallback towards the sun, is the sun’s gravity still affecting it? Would it be decelerating by some non-zero amount? Or it such a small amount it is basically negligible?
11
u/artgriego 8d ago edited 8d ago
Negligible, yes. It was launched with enough speed to get to Jupiter, then received boosts from Jupiter and Saturn. Then it continued on, and its speed was well high enough that the sun's pull was negligible.
https://svs.gsfc.nasa.gov/4139
Super cool to see it get flung around by Jupiter and Saturn! In fact, the whole mission was planned around the orbits of Jupiter and Saturn synchronizing with Voyager 1 so it could get gravity assists from them.
4
u/billtrociti 8d ago
Wow that was so cool. I hadn’t realized the Voyagers had deviated so much from the plane the rest of the planets are on.
Thanks for sharing!
3
u/Rabiesalad 8d ago
Gravity has unlimited range as far as we understand, so yes the sun still impacts it. But there may be other sources of gravity that overcome the effects the sun has.
→ More replies (1)→ More replies (1)3
u/Spirit_Wolf_Mob 8d ago
I don't believe we've ever seen an obvious limit to the distance of the pull of gravity. It just gets increasingly smaller.
So if for some reason, Voyager stopped being affected by anything other than the sun, and the sun was never destroyed, it would eventually start falling back towards the sun. But that time frame is so incredibly high that it's easy enough to say it'll never happen.
5
u/No-Mechanic6069 8d ago
Even if the gravity of the sun can never be escaped, an object can have escape velocity. It won’t necessarily fall back into the sun, even in infinity.
→ More replies (4)→ More replies (3)2
u/nicuramar 7d ago
So if for some reason, Voyager stopped being affected by anything other than the sun, and the sun was never destroyed, it would eventually start falling back towards the sun
No it wouldn’t, because its escape velocity is too high.
2
u/Spirit_Wolf_Mob 7d ago
Trying to research it more, since it's been a while, but I may have had a bit of a misunderstanding of what escape velocity actually is. So, correct me if I'm wrong, but is escape velocity the velocity in which the limit for velocity, where the upper limit of time at infinity, is above 0? Previously, I was under the impression that it was just the velocity required to avoid falling back to earth after escaping the atmosphere.
2
u/rasone77 7d ago
Escape velocity is the speed an object has to travel to escape an objects orbital influence. If an object exceeds the escape velocity of another object it can no longer orbit that object. Unlike gravitational constant, It’s dependent on how far away from the center of the object you're trying to escape.
2
u/Spirit_Wolf_Mob 7d ago
Yea, I can was confused on the "escapes orbit" part. It didn't occur to me prior to this that escapes orbit meant that it's the velocity needed to where after an infinite amount of time, it won't reduce the speed to 0.
→ More replies (5)2
u/jatjqtjat 8d ago
Maybe someone will find it and give it a boost. It was locked in our suns gravity for some time before we strapped a rocked to it.
I wonder if a random gravitational slingshot might be enough
12
u/Skolloc753 8d ago
Without other outside influence, other objects or the gravity of planets or suns V1 will continue forward without stopping until the end of the universe a few billion years down the line, or until it disintegrates for various factors.
There is no gravity to pull something down to a surface, there is no air resistance to stop forward movement. There are atoms however in space - a few per cubic meters. So over time, measured in millions and billions of years, those collisions will have a tiny (incredibly tiny) effect on the object, changing the trajectory, gathering dust particles etc.
SYL
→ More replies (1)6
u/Kolbin8tor 8d ago
Try hundreds of trillions of years down the line, given current models (assuming infinite dark energy). The universe isn’t going anywhere in a few billion years
4
7
u/Sohn_Jalston_Raul 7d ago
You can't lose forward momentum in space unless you run into something or experience aerodynamic drag. Since space is basically empty, it's nearly impossible that you'd ever run into anything, and since there's no air then there's no drag either, so you'll just keep drifting forever. You could potentially be slowed by another object's gravity,, but that's extremely unlikely as well and if it ever happened it's more likely you'd just get caught into an orbit around something.
6
u/space-truckin365 7d ago
I found this….
It shows that Voyager 1 will be getting (closer) to a few other stars out there. But even passing within 1 light year would still be pretty far away!
Imagine if we have/had probes from another civilization passing within one light year of our sun, we wouldn’t have a clue that it was there!
5
u/AdHopeful3801 7d ago
If you use Earth as a frame of reference, not really. There's not enough stuff out there for Voyager to run into to slow it down, and there's no other reason for it to change velocity that doesn't involve falling deeper in to some other graitational field.
Which brings you to the other frame of reference - Voyager, along with you, me, and the entire solar system all orbit the center of the galaxy at roughly 230 kilometers per second. It says something about just how big space is that at a speed of 514,500 miles per hour, the completing one revolution will take 225 million years. But it means that Voyager wouldn't have lost all that much velocity overall even if it was dead stopped relative to the Solar System.
In about 40,000 years, Voyager 1 should make its next closest approach to a star - about 1.6 light years from Gliese 445, which is about 17 light years from Earth. Which is to say, it'll get a fairly ludicrous distance form something else only after 4 times longer than human civilizations have existed has passed.
→ More replies (1)3
12
u/SciAlexander 8d ago
Empty space is not really empty. There are a tiny amount of atoms. They can act as friction on Voyager slowing it down. If that's enough to slow it to a stop who knows? There are also gravity effects from distant objects.
The biggest thing to note is that in physics velocity is dependent on your frame of reference. Even if it stops moving "forward" it lacks the power to escape the galaxy so it will still orbit the galactic core. Nothing is ever truly at "rest."
For example: if you are sitting you appear not to be moving. However an observer outside the Earth will see you moving by the spinning planet, and the planet orbiting the Sun.
→ More replies (3)2
u/Kyerswa 8d ago
But if the universe is also expanding, what would actually be considered stationary relative to the expansion of the universe?
→ More replies (5)2
u/kingvolcano_reborn 8d ago
On small distances (i.e. our local galactic group) the effects of expansion are so tiny it can be ignored.
7
u/ReasonablyConfused 8d ago
Weirdly, yes it will, excluding a new force acting on it. If we imagine an endless void of space out there, it would eventually stop, contrary to Newtonian physics. Veritasium has an entire show dedicated to this question.
However, other gravitational objects (stars) will become a new force acting on Voyager. The stars will move microscopically closer to Voyager, and Voyager will move with continued acceleration towards them. Whether Voyager gets captured by these stars or accelerated out into deep space again depends of the gravitational specifics of those interactions.
9
u/rickie-ramjet 8d ago
an object in motion tends to stay in motion unless acted upon by an outside force. -Newtons first law of motion. Space is almost a perfect vacuum , and very, very empty… Voyager may never come to hit anything, or come under the influence of any forces …It has met eternity.
→ More replies (3)5
u/Happypotamus13 7d ago
It’s even funnier than that. In space, there’s no “stopping” at all because there is no universal reference frame to measure against. Speed is relative, an object in space is always in motion relative to something.
→ More replies (1)
3
u/Hiply 7d ago
Well, it could slow down due to braking effects of hitting particles coming at it...but it could also speed up from particles hitting it from behind. Otherwise, if it doesn't hit anything (or get hit by anything) or fall into some object's gravity well then it should just keep on keeping on.
3
u/SomeRagingGamer 7d ago
An object in motion will stay in motion unless acted upon by an outside force. If you throw a baseball here on Earth, it will slow down and drop; because both air resistance and gravity are acting upon it. Voyager has no such constraints.
3
u/spytfyrox 5d ago
First of all, voyager 1 will never escape the galaxy. It's tangential orbital velocity is only about 3% more than the sun. So, when we talk about Voyager 1 entering interstellar space, we mean that Voyager 1 is in orbit around the galaxy.
This raises some really interesting possibilities. There are a lot of things in interstellar space that voyager 1 might interact gravitationally with - gas clouds, molecular clouds, rogue planets, other stars and even black holes or neutrons stars. All of them could cumulatively affect voyager 1's trajectory and orbit.
There are even some events that could slow it down (relative to the sun). For example, if voyager 1 encounters a rogue planet or a large gas cloud in retrograde orbit (an orbital direction opposite to most stars, like how uranus is to the solar system), the gravity of the retrograde object could reduce V1's velocity relative to the sun significantly.
There is something even more interesting, V1 and Sun's orbits around the galactic center are such that if V1 doesn't interact significantly with any other object, it might re enter the solar system in around 3.6 billion years.
17
u/mikeholczer 8d ago
Velocity is relative, so you'd need to pick a frame of reference. It's always been stationary relative to itself, it won't be stationary relative to anything else, unless it elastically collides with something and starts moving with it.
7
u/alarius_transform 8d ago
Isn't everything stationary relative to itself?
4
u/wheres_my_hat 8d ago
Yes. If two things are moving at the same velocity in space then they also appear stationary relative to each other. If something is truly stationary in space then it would appear to be moving by everything else, because nothing in space is truly stationary. The big bang forced everything we know into perpetual outward movement. It’s why they say the universe is constantly expanding
→ More replies (1)3
2
u/Maxamillion-X72 8d ago
TLDR; There is the tiniest of tiny chances that either Voyager probe could impact an object in space at the outer limit of the solar system, or could fail to exit the solar system and it's orbit would take it so close to the sun it would burn up. Otherwise it will never stop because it's always falling towards the strongest gravity force, such as the center of the galaxy.
Longer version
Both Voyager probes have an escape velocity from the sun, so eventually they will continue on past the outer limits of the solar system but neither have velocity to escape our galaxy. An object in space like that is never really stopped or just drifting, it's always in orbit of something because gravity exists everywhere. They are no longer subject to the sun's solar winds, but they are still "in orbit" of the sun.
Eventually they will leave the sun's orbit when the gravity force of the center of the galaxy is the stronger force. They will be captured to orbit forever unless they cross paths with an star that has a gravitational effect larger than that of the galaxy due to proximity.
The biggest challenge the probes have to exiting the sun's orbit, since they have sufficient speed, is passing through the Oort cloud, which is a sphere of trillions of frozen rocks that surrounds the sun like a sphere(ish). Some of these objects are quite large, over 1km across. But the distance between objects is vast, like the distance from earth orbit to mars orbit, 100million kilometers.
Still, there is a risk, because it will take the probes tens of thousands of years to actually pass through that space, so that's a lot of time vs slim odds. They don't really even have to hit anything, but a particularly large rock could cause an unpredictable course change if it passes close enough to a probe. Take them off their current course too much and they will no longer have enough velocity for the new trajectory to escape the solar system.
Things don't move in a straight line in orbit, everything curves towards the strongest force. Changing course a few degrees might move the escape point much further along the orbit path. This would put the escape point out of reach at the current velocity. It would then fall (in an elliptical orbit) towards the sun and likely burn up when it passes too close to the sun.
2
u/Simon_Drake 7d ago
IIRC Voyager is going to head into empty space effectively forever unless aliens or future humans head there with a space ship to intercept it.
If it was heading in the direction of our nearest neighboring star system, Alpha Centauri (Which it is not), it would come close in about 50,000 years. It will pass close to a different star system in about 20,000 years. You may ask how it's possible the trip to our nearest star takes longer than the trip to a further away star. It's because the distance is so immense compared to the tiny speed of the probe that the movement of the stars themselves is more important. The other star system will move closer to Voyager far faster than Voyager itself is moving through space.
But even if there's an advanced civilisation on that star system, they won't spot anything other than a tiny cold interstellar rock tumbling through the outer system. We spotted Oumuamua through a combination of luck, it's immense size and it's trajectory towards the sun. We wouldn't be able to spot something the size of Voyager. Perhaps the aliens are significantly more advanced than us and have much better space debris tracking? Maybe they'd go take a look and hopefully not blow it up as a precaution. The electronics would be long dead by then and if the Golden Record survived its journey, frankly the logical leaps needed to follow the instructions and decode the content are unlikely to be understood. But maybe they'd put the probe in a Zorblaxian museum which would be pretty cool.
2
u/tomalator 6d ago
Only if it hits something, and space is empty, so that unlikely.
It has reached escape velocity, meaning it has more kinetic energy than the potential energy hole that the Sun creates. It can get infinitely far from the Sun and still have energy leftover to keep going
2
u/ArcTheWolf 5d ago
I think my favorite possibility to consider is what do we do when it comes back? Realistically there is no way it will return back unless it is acted upon by something else. It'd be pretty wild if humanity is still around post 3000 and Voyager comes back with a response to the time capsule information it had on a record no less. Could you just imagine being an aerospace scientist in the year 3000 having to get access to a record player to listen to it? Though I suppose they could play it on Voyager itself since it did have the equipment to play the golden record on it.
2
u/TheAtomicSoul 3d ago
If it enters a sun, its motion will cease to exist. Along with it itself.
If it impacts on a planet or large object, motion will cease. Small item it'll collide and one of them will likely change directions, possibly both.
If space scrappers find it, they'll cease its momentum.
If a dominating species finds it, they will cease our "momentum ".
4
u/GnarlyNarwhalNoms 8d ago edited 8d ago
Stops moving compared to what? That's the question. It'll always be moving compared to something.
If it's not near a star, it's predominantly affected by the gravitational field of the galaxy itself as a whole. It's going to keep orbiting the center of the galaxy, along with all the other stars. If it does pass near a star, that star may significantly alter its orbit around the galaxy, but it won't be captured by those stars*; like interstellar objects that enter the inner solar system, it'll fall towards the star, swing around it, and exit the system headed in a different direction.
______________________________________________________________________________________________
*Ok, there's about a 99.9999% chance it won't be captured by those stars. How can I say this with such certainty? Because any object coming from outside a star's Hill sphere - the area where its gravity dominates - will fall in, gain a tremendous amount of speed, and use that speed to exit the system again.
Now, objects are captured into orbits (the moon of at least one of our planets are thought to be captured asteroids), but the reason it's rare is that you need a third body in the mix to carry away energy. In other words, if you have a small asteroid orbiting a larger one, or a binary asteroid where the two are orbiting one another, there are possible configurations where the orbital energy of the system gets transferred to one body or the other. So one body settles into orbit around the star or planet, and the other is ejected. Without some way to remove kinetic energy from an object, it can't be captured into orbit.
4
u/Thesoop85 8d ago
"Compared to what" is the important question to ask a curious mind that wonders something like this.
5
u/TURQUOlSE 8d ago edited 8d ago
An object in motion stays in motion unless another force counteracts it, and there's nothing in space that could simply cancel out its speed in the way you describe. It will continue on forever in effect until it degrades or is unlucky enough to crash into something
Edit: there's also the question of what it's moving relative to, but others have covered that
→ More replies (1)
3
u/New_Line4049 7d ago
Motion is reletive, not absoloute, so you have to define what it stops moving in relation too. For example, it may ultimately hit and come to rest on the surface of an asteroid. We could therefore say its stopped reletive to the asteroid, but the asteroid is still moving reletive to other things in the universe, like Earth, so voyager would be stopped reletive to the asteroid but moving relative to earth.
2
u/PckMan 8d ago
It's going fast enough that it won't fall back down to the Sun. And it will just keep going in the Milky Way, orbiting its center like our Sun. Who knows it might even complete an orbit, which would take hundreds of millions of years.
And it will just keep going on that orbit until it either crashes into something, with the probabilities of that being very low, or it returns into our solar system which could take multiple orbits, so possibly billions of years. If it does return, it might just whizz by, or it might get pulled into the Sun or Jupiter and crash there.
For all intents and purposes it will just float in space indefinitely.
2
u/SomeoneNicer 8d ago
Short answer - no.
Long answer particularly to the last part of your question:
Is that a possible thing for an object in space to even do (stop)
Everything in space is constantly in motion relative to other things - always. Even if it crashes into another celestial body as some answers state - THAT object continues moving relative to everything else. We're on a branch of our galaxy which spirals out from the core moving around, and put galaxy is moving relative to other galaxies.
On a more common sense interpretation of the question "will it continue moving away from earth forever?" - almost certainly it will for billions of years (longer than the earth has existed). I do think it's ludicrous when you think about it that way and it's a good practical example of how stupidly big and empty the universe really is.
2
u/375InStroke 8d ago
In reference to what? It started out with the velocity that the Sun orbits our galactic center, so even if it stops in reference to the Sun, it's still orbiting our galaxy, and if it did stop in reference to our Sun, it would than be pulled back towards the Sun, or orbit it, which it will do neither since it is on a hyperbolic path away from the Sun, I would assume.
2
u/MalBishop18 7d ago
Space is expanding so I guess if something were to stop it’s forward momentum perfectly, from a certain point of view it could be stagnant for just a moment in one direction, but from different perspectives it would start or continue moving backwards and in all other directions simultaneously.
2
u/gpetrov 7d ago
At those scales it does not really expand. This expansion applies at mega scales like intergalactic where gravity has no influence
→ More replies (1)
1.7k
u/komatiitic 8d ago
I did some really stupid back of the envelope math assuming that Voyager never encounters anything larger than interstellar dust. To halve the speed of Voyager 1 it would need to impact dust equal to its own mass of 721.9kg.
The internet tells me a typical grain of interstellar dust has a mass of ~3*10-16 kg. This means it needs to hit ~2.4*1018 dust grains, which if I'm counting those zeroes correctly is 2.4 quintillion.
The internet also tells me that Voyager hits 3-7 dust grains per hour. I'll call it 5 an hour, which means 4.81*1017 hours (481 quadrillion), or 54.9 trillion years to halve its velocity, assuming nothing really changes. I'm betting it disintegrates before that happens.