[Physics] Galilean Moons

[Thomas Goodey]

On 7 Aug 2017 at 12:00, physics-request at tuks.nl wrote:

> Bonus:  IF the prediction math is good enough, say to the
> nearest thousandth of a second

It can't be. We don't know the orbits of the GMs accurately 
enough, and anyway, events of that type don't have accurate 
temporal boundaries. They come on slowly and go off slowly. 
An observer from afar won't be able to localize the event 
in time to an accuracy better than some seconds.

> ... and we each have equally
> accurate wristwatches

People don't use wrist watches for astronomy.

> we may also get a "one-way speed of
> light" as well.

It won't work. It's a nice idea, but it won't work. It's 
nowhere near accurate enough.

And anyway, even if you could fix the timing of the event 
to an accuracy of a thousandth of a second (which is 
utterly impossible), considering that the light-travel-time 
to Jupiter is around a thousand seconds, you would only be 
able to derive the one way speed of light to an accuracy of 
one part in a million, which is not at all precise in terms 
of light speed measurement. As Wikipedia tells us, before 
the redefinition of the meter, "... in 1975 the speed of 
light was known to be 299,792.458 m/s with a measurement 
uncertainty of 4 parts per billion".

There is also the problem that this method only works one 
way. You can't even start to derive the speed of light the 
other way, from us to Jupiter.

Thomas Goodey

*****************************
Anne's search for security 
holes in the localizer network 
software was close to 
impossible. Every year her 
zipheads pushed back their 
deadline for certainty another 
year or two. But the quagmire 
of Qeng Ho fleet software 
was almost eight thousand 
years deep.
--------- Vernor Vinge
----------'A Deepness in the Sky'