Voyager 1's clock

siarad · Mar 16, 2005

Voyager 1 has been travelling about 27 years so it's clock must be well behind ours. It seems this means it must be actually running more slowly than ours i.e. time dilation. From this the transmitter frequency must be continuously reducing i.e. red shifted. Does anyone know if this is so & by how much the Tx frequency has reduced indicating the time dilation.

vogon13 · Mar 16, 2005

Seems odd to characterize a radio signal that has been reduced in frequency due to motion of the transmitter away from us a 'red shifted' but I know what you mean. The carrier frequency of Voyagers radio is indeed lowered by an amount apprpriate to its' recessional velocity from earth. Keep in mind the frequency of the signal at the receiver will also show variations due to earth's motion around the sun (this varies throughout the year) and another variation is due to earth's rotation. All of these effects are known and can be calculated to high precision and the signal from Voyager 'meets expectations'. There were some subtle effects from the Pioneer signals, but you didn't ask about that. Time dilation effects for an object traveling under 50 km per second are going to be small, but perceptive of you to consider them. There are some equations that others will post here to help you calculate all these effects. An additional effect you didn't bring up is that both Voyager craft are also shorter (relative to us) in their direction of movement than when they were sitting on earth's surface. This difference is also quite small. When the Voyager craft were closer to the plane of the ecliptic, the sun's gravity also effected their signals during the time of year when their signals passed close to the sun on their way to earth. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

CalliArcale · Mar 16, 2005

<blockquote>In reply to:<hr />Time dilation effects for an object traveling under 50 km per second are going to be small, but perceptive of you to consider them.<hr /></blockquote> Small, yes, but measurable. Time dilation was first experimentally proven using supersonic aircraft! For satellites, it is also measurable as they are going quite fast relative to an observer standing next to an atomic clock on the surface of the Earth, but I believe gravity has more of an affect there, although I confess I'm very shaky on relativity still. I do know for a fact that GPS receivers have to make a relativistic correction to the time signal they get from the GPS satellites. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

Leovinus · Mar 16, 2005

I do know for a fact that GPS receivers have to make a relativistic correction to the time signal they get from the GPS satellites. Einstein would have loved to see that. <div class="Discussion_UserSignature"> </div>

yurkin · Mar 16, 2005

That’s an interesting question. I wonder how much younger the Voyagers are. They must have a clock of some sort tied into the computer. It could be calculated since we know the velocity of Voyager at each moment of its trip due to the Doppler shift in the radio signals. But that would be a lot more work to calculate.

yevaud · Mar 16, 2005

I did a brief, off-the-cuff calculation of this. Using the formula T (Tau)=T0/Sqrt(1-(V^2/C^2)), I came up with a Tau of 0.9999999805. That's the factor by which their clocks will be off, compared to ours. Which is to say, that over, say, a span of 1 year: 1 year=31,557,600 seconds 31,557,600 seconds * Tau =31,557,599.38 seconds So over the span of 1 year, Voyager 1 is 0.61537 seconds off from the stationary observer. Since Voyager 1 was launched (again, ballpark) about 27.5 years ago: 27.5 years * 0.61537 time difference = 16.92 seconds. So (and remember, these are very "back of the envelope calculations), Voyager 1 is some 16.92 seconds behind our stationary clocks. Mind you, to make it simple, I assumed that 99.99% of it's voyage was at it's current velocity, which was not the case. But this is a reasonable approximation (it's been years since I had to figure this. Hope I did it right). I had to make some gross assumptions in the lack of exact figures... <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

siarad · Mar 16, 2005

Thanks & Yevaud but I'm not good with words & I seem to have failed to put my point over or misunderstand time dilation. Thanks for the calculation Both are answers but it's not recessional shift that I meant. If there's time dilation then the voyager clock hasn't just lost time but surely will be running more slowly & time will be affecting the resonant circuits causing the Tx frequency to be slow w.r.t. us. The total time lost is obviously the sum of each time lost, I don't know if time is granular, so does the clock actually run more slowly or just keep losing time. Sorry my words aren't good but two things seem to be happening & I can't explain the difference as the only word I know is 'time' for both which is why I tried the illustrative Tx frequency to attempt to separate it from recessional frequency.

yevaud · Mar 16, 2005

Ah, I see. The clock on Voyager will continually run slower than one that's stationary on Earth. That's what the "Tau" equates to. Meaning (using the Tau figure I came up with) that for every second we experience, Voyager experiences 0.9999999805 seconds. So, as your velocity increase more and more, Tau will decrease, which equates to your clock will run proportionally slower and slower. Is that what you meant? And, np about the calculations. As I said, I hadn't had to do it in years and years. I kind of enjoyed it. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

Leovinus · Mar 16, 2005

Voyager should be slowing down due to climbing out of the Sun's gravity well. <div class="Discussion_UserSignature"> </div>

yevaud · Mar 16, 2005

Didn't even take that into account. And I expressed this as the reciprocal of how Tau is usually used (it'd normally be expressed 1.xxxxxxx). I double-checked my calcs, just to be anal retentive, and my back-o-the-envelope figures are pretty close. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

vogon13 · Mar 16, 2005

I realize the eccenticity of the Voyagers orbits around the center of our galaxy will scarcely be different than that of the solar system, but would a teeny tiny adjustment factor lie in their differing positions relative to the center of our galaxy and its' presumed black hole? This would be one of those 'math' things that I try to avoid, doncha know. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

vogon13 · Mar 16, 2005

I don't know if time is granular That is very profound! And nobody knows. Seems like there was an observational analysis of some of the distant quasars that seemed to imply time is non-granular (as you put it) down to (IIRC) 10^-43 seconds. And that is pretty ungranular. And of course, maybe down around 10^-600 seconds or so, it turns out to be noodley or something, and then what? <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

yevaud · Mar 17, 2005

Hey, that's pretty good! Hell, since what happens to you if you fall deeply into the influence of a singularity's gravity is "spaghettification," why not "noodly?" One question...if I spiral into a gravity well, am I "Rotinied?" <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

vogon13 · Mar 17, 2005

Well, I'm not sure that word would have occured to me or any of the other me's in any of the other earth's in all the multiverse. But since you brought it up, it does seem apropo. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

siarad · Mar 17, 2005

When I started this I didn't know what was worrying me but 'it's good to talk' so I'm more clear now. There should be a difference between recessional red-shift & that due to time dilation. Is a clock running more slowly actually a measurement of time slowing or an affect seen externally. As we know the recessional red-shift it seems to me we have an ideal chance to see if time has really slowed on Voyager 1 as the Transmitter frequency would be lower than on earth. I don't mean the received frequency which is recessional shifted. Just an aside, stopping Voyager 1 w.r.t. earth would put the frequency back up as time would be again synchronised with us so where did those lost seconds go. Maybe I should start a topic on that <img src="/images/icons/laugh.gif" />

yevaud · Mar 17, 2005

It is hard to grasp. But that time is neither gone nor retrieved. If you were to stop Voyager dead in it's tracks now, Voyage will be forever 16-odd seconds "younger" than us. This is actually a very tiny time dilation effect. It's minimal for anything moving at a velocity of under about 300 m/s (and Voyager is only at 17.46 m/s). Remember, it took 27.5 years for it to end up only 16-odd seconds off. The red-shifting (or blue-shift, it's all the same) and the time dilation are part and parcel of the same thing. Voyager could be heading for us, and so blue-shifted, not red, but the time-dilation would be the same. While the dilation effect is a function of velocity, the red/blue shift is a function of velocity and magnitude (direction). <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

vogon13 · Mar 17, 2005

Einsteins' twin paradox. <div class="Discussion_UserSignature"> TPTB went to Dallas and all I got was Plucked !!So many people, so few recipes !!Let's clean up this stinkhole !! </div>

yevaud · Mar 17, 2005

Exactly. Which reminds me of an old ditty about it I'd read once. "There once was a woman named bright Who could travel faster than light She left one day, in a relative way And returned the previous night." <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

najab · Mar 17, 2005

>It's minimal for anything moving at a velocity of under about 300 m/s...I'm fairly sure you meant km/sec - otherwise there should be a lot of *really* young SR71 pilots around. <img src="/images/icons/wink.gif" />

yevaud · Mar 17, 2005

Er, yes, km/hr. (or 0.0001 C). Sorry. Gotta learn to type slower... <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

najab · Mar 17, 2005

>Er, yes, km/hr....Not really making it any better here: ("It's minimal for anything moving at a velocity of under about 300 km/hr..")Not been your morning, has it? <img src="/images/icons/laugh.gif" />

yevaud · Mar 17, 2005

I should probably wait until I suck down more coffee, before firing up the 'puter and posting, yeah. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

siarad · Mar 17, 2005

Frequency shifting & time dilation are not one of the same thing. As you say a satellite approaching is blue shifted & red shifted on receding but time dilation is always positive so is not the reason for motion frequency shifting which is what I am trying to find. I see two different effects but don't know if that's so as once motion stops so does time dilation & that's why I thought the Tx frequency may show the effect. Current satellites have been in use for a short time & at low speed for this possibly not to be seen. However Voyager 1 has achieved remarkable longevity in it's large distance travelled & higher speed so that time dilation should be measurable. At the moment we have formulae & clocks that do lose time but I don't know whether that is truly time loss or natural effect. Yes particles travelling at high speed do live longer than ones produced on earth but is it 'cos their time has changed or some other reason. An oscillatory circuit used in a transmitter doesn't, perhaps, rely on these physical properties so could actually measure time by being reduced in frequency or, if time hasn't changed not varying in frequency. The components for resonant frequency are some form of Inductance & Capacitance whose values are at least proportionately determined by Space, in S.I Units, but I don't see any time there other than hidden in the 2pi of the resonance formula. I can't find a way of drawing formulae here but have seen it topics.

yevaud · Mar 17, 2005

Well, let's see. I'll break this down, and try to answer each. As you say a satellite approaching is blue shifted & red shifted on receding but time dilation is always positive so is not the reason for motion frequency shifting which is what I am trying to find. They're like two different aspects of the same thing. Time dilation is always negative (not positive), meaning you (the one moving at relativistic velocities) will always lose time. Red- or blue-shifting is a function of velocity, but also magnitude (vector). Look at it this way. At this point, Voyager 1 is receding from us at a certain velocity. It simultaneously will show a red-shift because of the recessional velocity/magnitude, and also a tiny loss in time due to the time dilation effect. I understand what you were asking on this, about onboard time, and that was a very good question. Had to think about it for a minute. I would think that along with the red-shifting, there would also be a tiny "slowing down" of the data transfer, because it's also out of synch by a fraction of a second with the stationary receivers - meaning that (example) we're at 60hz, and Voyager is at 59.9999999 herz, if you see what I mean. Yes particles travelling at high speed do live longer than ones produced on earth but is it 'cos their time has changed or some other reason. In the context you're asking, you're correct - it is because of their time has changed. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

siarad · Mar 18, 2005

Yes you obviously see what I'm pointing out but not quite why. Everyone seems to say 'it's relativity, shrug shoulders, live with it & walk away'. The problem is I can't. Just 'cos we devise clocks to measure time we say it must be but I'm asking can we use Voyager to measure time in a different way not by clocks we know vary in time. The oscillatory circuit is just moving energy between L & C not relying on atomic decay etc. I guess the electrons involved could be equally affected by time. I've read that less than 10 people understand relativity but am perturbed that I can't find an explanation as why it happens. If a person was on voyager, as time isn't granular & discounting the spacial difference, he would have seen all the things we on earth had but more rapidly, having less time in which to see it all but wouldn't know it, why?

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