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Offline GreatATuin

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Moons of Jupiter and the speed of light
« on: May 03, 2020, 12:07:19 PM »
Jupiter has many natural satellites, but only four of them are so big and bright they were identified by Galileo more than four centuries ago. They are now known as the Galilean moons: Io, Europa, Ganymede and Callisto.

Even with a small telescope, it's possible to witness from Earth the Jovian equivalent of our eclipses: moons casting their shadows on Jupiter, moons being eclipsed by the shadow of Jupiter. See https://www.space.com/6705-moon-shadows-jupiter.html :

"The shadow of the moon, cast by the sun, can also be seen to transit across the cloud tops. Because the shadows are intensely black, they are much easier to see than the moons themselves.

When a moon passes behind the planet, it can be occulted by the planet itself, or eclipsed by Jupiter's immense shadow. You can even watch a moon emerge from behind Jupiter, glow brightly for a few minutes, and then fade from sight as it enters Jupiter's shadow."

A number of sites give the times for each event (occultation, transit, shadow, eclipse), for example:
http://shallowsky.com/jupiter/
https://skyandtelescope.org/wp-content/plugins/observing-tools/jupiter_moons/jupiter.html

Jupiter is so big and bright it can even be seen in daylight conditions: https://www.skyatnightmagazine.com/advice/skills/jupiter-moons-double-transit/

Depending on where Jupiter, the Earth and the Sun are, eclipses will be seen after or before occultation. A few months after opposition, the two outermost Galilean moons (Ganymede and Callisto) can be seen to disappear behind Jupiter, reappear, and then disappear again in Jupiter's shadow: https://books.google.com/books?id=w9URBwAAQBAJ&pg=PT133&lpg=PT133&redir_esc=y#v=onepage&q&f=false . The same phenomenon cannot be observed for Io and Europa because their orbit is too close to the planet: the eclipse starts before the occultation ends or the occultation starts before the eclipse ends.

Variations in timing of these eclipses were used by Danish astronomer Ole Rømer to make the first estimation of the speed of light in 1676, when at that time light was thought to propagate instantly and have an infinite speed. Rømer's first estimation was too low, but definitely in the right ballpark (see also http://www.phy6.org/stargaze/Sun4Adop1.htm ). The same method was later used to make more refined estimations that were in line with the current accepted value of c.

Now, on a flat Earth:

1) Is our Sun the source of light for the Jovian system?
2) If not, then what is it?
3) In any case, how far is the light source from Jupiter and its satellites?
Nearly all flat earthers agree the earth is not a globe.

you guys just read what you want to read