
#19
Nov1412, 03:08 PM

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P: 10,766

The distance can be evaluated via timing  not very precise, but probably good enough as the probes are far away from any massive object and their position is not so crucial.




#20
Nov1512, 02:37 AM

P: 344

Also a way of calculating this ? 



#21
Nov1512, 04:46 AM

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P: 10,991

Try this link: http://www.au.af.mil/au/awc/awcgate/...ic/bsf131.htm
And here: http://www2.jpl.nasa.gov/basics/bsf131.php 



#22
Nov1512, 04:47 AM

P: 615





#23
Nov1612, 01:49 AM

P: 344

The gravitational field of the Earth is causing the signal to blueshift and the speed to the sigal to redshift, so this is how we measure the speed . OK
Let us say that right now we expect the speed of the space probe to be12000m/s Let us say that time is ticking 1 nanosecond faster at the space probe (due to gravitational time dilation) as 1 second on the Earth. . Do we expect the space probe to move 12000 m/s (per 1 Earth second) or 12000 m/s (per 1 Space probe second) ? (To keep it simple ignore the influence of SR, so only GR influence is the question ) 



#24
Nov1612, 07:50 AM

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P: 10,766

The measurement is done on earth, but you can transform it to other systems as well of course. 



#25
Nov1712, 01:45 AM

P: 344

Let's say right after launch the speed seen from that reference frame is exactly 12000 m/s After some decades when leaving the solar system times ticks faster compared to time on Earth, seen from the space probe reference frame. How fast will the speed of the space probe be after reaching the edge of the solar system,  still seen from the perspective of the space probe ? I guess still 12000 m/s , also even though that time now is ticking faster as before?? And seen from the perspective of Earth it will look like the probe is acceleration, proportional to the time dilation,  or ? We will ignore the backwards pulls due to gravity of the solar system 



#26
Nov1712, 02:25 PM

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If we expect the probe to move 1200m/s relative to the sun in the system of the probe, we expect it to move 1200m/s in the system of the probe and with its own clock. Well, it has no precise atomic clock, but we can imagine one. I don't get the point.




#27
Nov1812, 01:55 AM

P: 344

Do you mean the speed also is 12000 m/s seen from the RF of the Earth?,  that wouldn’t be possible.' Because time is ticking comapable slower on Earth, we on Earth cannot agree that speed is the same as seen from the perspective of the space probe,  (or ?) What is the solution to that? 



#28
Nov1812, 09:09 AM

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P: 10,766

If we ignore deceleration, we have to ignore gravitational time dilation as well, as they are both parts of the same effect (gravity). You cannot get one without the other. Without gravity, both earth and the probe will measure 12000m/s all the time. 



#29
Nov1812, 10:11 AM

P: 344

So what you say is that the speed out of the solar system, seen from the perspective of the space prove is "constant"  but MINUS the deceleration due to gravity ? 



#30
Nov1812, 11:03 AM

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P: 10,766

If you calculate the deceleration in the system of the probe.
If you calculate the deceleration in the system of earth, you get a different value due to gravitational time dilation. You can calculate the system as a whole, but it is quite pointless to split it in arbitrary components to compare them. 


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