Re: Saturn and speed of light

"Iordani" <somewhere@xxxxxxxxx> wrote in message
news:4bctp9F10ujovU1@xxxxxxxxxxxxxxxxx
Jo wrote:

In news:4bcnjoF10tq0vU1@xxxxxxxxxxxxxx,
Iordani <somewhere@xxxxxxxxx> typed:

The time for any moon to be in the dark cone of Jupiter would be the
same, regardless of the distance between Earth and Jupiter. As
observed from Earth, that is.

By my way of understanding things, that is.

Which is wrong.

It is not the time in the dark cone time that varies, it is the time
between each dark cone event. As the Earth-Jupiter distance increases
the
events are seen later and as the distance decreases they are seen
earlier.

Right, so the ability to measure time in 1676 was that accurate?
If this is the case, then it's all quite clear.
(In fact, I did rule out that possibility)

Thanks you

Clocks were not all that wonderful in 1676, but good enough for astronomers
to be able to check them each night against the stars. The measurement
errors would have been of the order of seconds to a minute or so, as clocks
could be adjusted by watching stars with a transit instrument. Around this
time Christiaan Huygens was perfecting his methods of building accurate
clocks, but I don't recall if Roemer used one of these.

The total variation of timings would have been a range of 16 minutes, so the
timing methods were good enough for this.

By 1676 a reasonably accurate scale of the solar system had been determined
from the parallax of Mars. Good to a few percent, anyways. This made it
possible for Roemer to determine his result.

--
Mike Dworetsky

(Remove "pants" spamblock to send e-mail)

.

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