Why did Voyager 1 need a map indicating its origin?

[Voyager55]

Why was it necessary? If any species advanced enough to be retrieving alien artifacts drifting through space, also be able to calculate its trajectory backwards across millions or even billions of years? Based on the crafts velocity, and where stars were at specific points of time, and their effects on the crafts trajectory, shouldn't it be somewhat of an easy task for a team of alien astrophysicists to calculate where Voyager 1 set off from?

[YNM]

For coolness. Or whatever Carl Sagan had in mind.

Trajectory related - a galaxy is basically an n-body system with friggin amount of perturbation. You can't expect a single star (let alone a single probe !) to have a highly precise fixed trajectory over millenias. While they may say a region, knowing which one is it truly is hard. Even so, I doubt that using pulsars would improve it anyway, more so if they're within milky way itself.

[Voyager55]

For coolness. Or whatever Carl Sagan had in mind.

Trajectory related - a galaxy is basically an n-body system with friggin amount of perturbation. You can't expect a single star (let alone a single probe !) to have a highly precise fixed trajectory over millenias. While they may say a region, knowing which one is it truly is hard. Even so, I doubt that using pulsars would improve it anyway, more so if they're within milky way itself.

Oh yes, true. Any galaxy is a giant N-body soup. But I still think using physics and calculations would be the easiest way to find the origin of departure.

[NovaSilisko]

It was really just a symbolic gesture. It wasn't just the map also; pioneer 10/11 had just the map, while voyager 1/2 had the whole golden record deal with recordings of speech and music and general sounds of earth (as well as images encoded in an audio format).

[Voyager55]

Ah, I understood the whole golden record part. Just not the need to display our location, as they could probably figure that out in a heartbeat. But I suppose it could be a nice symbolic gesture, kind of, "Here we are, come on in."

[basic.syntax]

I pulled out my copy of Cosmos, and it's discussed on page 287. It was not primarily intended to indicate our planet's location, but to share with the discoverer a cross-section of what it means to be human, if that is even possible. (If it doesn't get used for target practice, or vaporized as random space junk by passing aliens )

Many, perhaps most, of our messages will be indecipherable. But we have sent them, because it is important to try. [...] Perhaps the recipients will make nothing of it, or think it is a recording of a pulsar, which in some superficial sense it resembles. Or perhaps a civilization unimaginably more advanced than ours will be able to decipher such recorded thoughts and feelings and appreciate our efforts to share ourselves with them.

[kerbiloid]

1. Because a hundred years later a space yacht from Earth will chase Voyager and take it aboard.

And a golden plate covered with a couple of humans and a space map with meteorite nicks will look great.

2. Suddenly Voyager wants to get back to home. How should it find its way without a map?

[YNM]

Oh yes, true. Any galaxy is a giant N-body soup. But I still think using physics and calculations would be the easiest way to find the origin of departure.

Hmm... Well yeah, they stated that there should be no perturbations in the first hundred millenia. Not sure of the rest...

Carl Sagan's mind, then.

[Nibb31]

The purpose of the messages on Voyager and Pioneer probes was PR, nothing else. It was a way to put something meaningful for the general public.

Nowadays, NASA does "fly your name to space" where your name gets burned to a CD or a thumb drive that is stuck on the probe or rover. It's just as meaningless, because nobody will be ever be able to read that CD.

Edited June 19, 2015 by Nibb31

[Lukaszenko]

I think it was more for us than for the aliens. Logically it doesn't make sense, but somehow form a human standpoint, it does.

I guess that's in line with what Nibb31 wrote.

[RainDreamer]

I think it is meant to say "This place on the map is our home" rather than "This is the place we send our probe from". Subtle differences. It is not just giving information about where we are, but also a declaration : This is us, we are human, inhabitant of Earth.

[Eric S]

I think of it as insurance against the longshot of a hard to detect rogue planet deflecting the trajectory of the probe by enough to make backtracking the trajectory impossible without knowing about said rogue planet. Yes, that's a very long shot, but it would stink to high heaven to go through all the work just to have that happen.

[Wesreidau]

I think of it as insurance against the longshot of a hard to detect rogue planet deflecting the trajectory of the probe by enough to make backtracking the trajectory impossible without knowing about said rogue planet. Yes, that's a very long shot, but it would stink to high heaven to go through all the work just to have that happen.

More mundane; how much cosmic background radiation will this probe be going through across how many million years, and will that force fluctuate over time. Think of it as tracing back an envelope. Sure, you could get every fingerprint and fiber of everything that touched it and back-track throughout the postal service. You could also read the return address.

Perhaps more importantly, adding a map indicates an interest in establishing contact. If I throw a brick across the street that says "Hello! Here's a picture of my family!" it is a little creepy. "Hello! Here is a picture of my family and we live just across the street from you!" its still creepy by way of a bad analogy, but its at least implied we'd like a brick thrown back with alien family vacation photos.

[Hal]

I could be very mistaken here, as I feel like I'm forgetting some basic part of orbital mechanics, or maybe just some basic part of logic. But wouldn't the aliens only be able to find where Voyager had come from by backtracking if it hadn't made any extra burns? They wouldn't have any particular reason to assume that the probe didn't, say, perform a 200 dV burn (and then detach the propulsion stage) after reaching a light-year from Earth, or any other one of infinite possibilities that would throw off tracking through simple gravity.

I do feel like I'm missing something though, so take that with a big grain of salt.

[Wanderfound]

Obligatory West Wing scene:

And Blind Willie himself:

[vger]

@Wanderfound: Deep.

Really... frikkin... deep.

[Nothalogh]

Why was it necessary? If any species advanced enough to be retrieving alien artifacts drifting through space, also be able to calculate its trajectory backwards across millions or even billions of years? Based on the crafts velocity, and where stars were at specific points of time, and their effects on the crafts trajectory, shouldn't it be somewhat of an easy task for a team of alien astrophysicists to calculate where Voyager 1 set off from?

To leave no doubt of our origin. http://creepypasta.wikia.com/wiki/Mankind

[Dispatcher]

Why was it necessary? ...

So it could find its way home.

[heng]

[...] by backtracking if it hadn't made any extra burns? They wouldn't have any particular reason to assume that the probe didn't, say, perform a 200 dV burn (and then detach the propulsion stage) after reaching a light-year from Earth, [...].

Scale!

Think in longer terms. This was not for potential extraterrestials within a few light years distance, those could figure out something is happening here without a map. This was intented to be read thousands, or(*) millions of years in the future. A single encounter with a rogue planet unknown to the recipient, even if it influences Voyager's path by a minute amount, would make it neigh impossible to get a correct location by backtracking. RL is not KSP's simple 2-body physics. You would need to know the location, mass, velocity of every single piece of relevant sized mass along the path.

Another factor had earth scientists baffled for decades. The RTG did not uniformly radiate its heat, and influenced The Pioneer probes to a measurable amount over the distance. IIRC 15min arrival time difference over two/three decades? And these decades were spent wondering with full access to the blueprints.

What I want to see on the next message-in-a-bottle mission is this:

A defined amount of ultra pure Uranium 238. (not 235)

A description of how to measure exactly with how much this started.

A description of the full decay cascade.

With knowledge of the half life (more than a billion years) and some decent measurements one can easily determine the probe's true age...

--

(*) Wanderfound is right, my bad.

Edited July 3, 2015 by heng
eternal edits *sigh*

[kiwi1960]

The Voyager contained a message from Earth.... it showed a naked man and woman, indicated where we were in our solar system, and using hydrogen atoms, where we were in the Galaxy... any species smart enough to figure that our will also be able to make sense of the metal LP with the sounds of our world, "Hello" said in every language on the planet, children laughing, birds, cats, dogs....

They don't expect any alien species to actually come and hunt us out if they do find it, but just letting them know they are not alone, that we exist (or did, once) and where we are....

If we ever had an alien version of Voyager arrive in our system, I'd wonder who made it.. where it came from.... who we are... what we are....

Voyager answers all that for THEM.... they should accept it as a peaceful gesture given that if we didn't tell them, they might assume it was a spy probe and an act of war....

Have you seen the movies of aliens landing here and attacking Earth? We are afraid of them as much as they may well be afraid of us....

and its better than saying nothing at all.... it cost nothing to send it with Voyager... its completed its mission so why not?

[Sharpy]

Oh yes, true. Any galaxy is a giant N-body soup. But I still think using physics and calculations would be the easiest way to find the origin of departure.

Many thought that before. Then that friggin' dark matter was discovered.

Observe the motion of planets in the solar system. For one orbit of Neptune, Earth makes several hundred.

Now observe the shape of the spiral galaxy. For one orbit of one star at the end of the most extended arm, there is maybe one and a half orbit of a star near the very core.

Plain orbital mechanics of n-body system doesn't apply to motion on galactic scale. There's *some* mass that binds it like a moderately flexible body or a very thick liquid. It's that theorized Dark Matter. It's not mapped out and likely very difficult to be mapped, and it totally skews any trajectory calculations on that size scale.

[Wanderfound]

Scale!

Think in longer terms. This was not for potential extraterrestials within a few light years distance, those could figure out something is happening here without a map. This was intented to be read thousands, or millions of years in the future. A single encounter with a rogue planet unknown to the recipient, even if it influences Voyager's path by a minute amount, would make it neigh impossible to get a correct location by backtracking. RL is not KSP's simple 2-body physics. You would need to know the location, mass, velocity of every single piece of relevant sized mass along the path.

Even thousands of years in the future, Voyager is still going to be right next door to Earth from a galactic point of view. As you say: scale.

Not directly Voyager related, but a useful graphic for demonstrating the ridiculous bigness (to paraphrase Douglas Adams) of space:

http://www.planetary.org/blogs/emily-lakdawalla/2012/3390.html

[YNM]

The probe (considering the U238 on the plate) might be designed for a long time, maybe billions and billions and bilions... of years ? On that level every attempt to trace back which star were it are pretty much trying to rewind time or trying to tell the momentum of an electron and it's position very accurately at the same time.

Edited July 2, 2015 by YNM

[vger]

Even assuming an advanced race could construct an accurate model of the entire galaxy's motion for navigational purposes... anyone want to take a guess at the amount of memory that would be required to store all of that information?

Still an interesting OP question though. Voyager is expected to reach another star in about 40000 years. Now that it has reached interstellar space, the odds of it ever being intercepted before that time is greatly reduced, unless those aliens have a darned good telescope hunting for rogue objects.

[YNM]

Many thought that before. Then that friggin' dark matter was discovered.

Observe the motion of planets in the solar system. For one orbit of Neptune, Earth makes several hundred.

Now observe the shape of the spiral galaxy. For one orbit of one star at the end of the most extended arm, there is maybe one and a half orbit of a star near the very core.

Plain orbital mechanics of n-body system doesn't apply to motion on galactic scale. There's *some* mass that binds it like a moderately flexible body or a very thick liquid. It's that theorized Dark Matter. It's not mapped out and likely very difficult to be mapped, and it totally skews any trajectory calculations on that size scale.

There's no real well-predicted orbital mechanics for an n-body system, because there's always perturbations here and there... Even without dark matter. You can't tell precise paths, you only can tell groups of objects at best.

Voyager is expected to reach another star in about 40000 years. Now that it has reached interstellar space, the odds of it ever being intercepted before that time is greatly reduced, unless those aliens have a darned good telescope hunting for rogue objects.

And that's 1.6 ly away from the star (gliese 445)...