# Is the two events of an orbiting moon of Jupiter added together to calculate the actual moment?

An observer on earth watching the orbit of a moon around Jupiter.Jupiter is at it's farthest distance from earth roughly 601 million miles which takes light roughly 54 minutes to arrive to earth. When the event of the moon during the observation of the moons orbit passes behind Jupiter the observer views the event happening 54 minutes in the past and the event of the light reappearing at 54 minutes in the past. So does the observer on earth view the whole event 108 minutes in the past for each orbit observed?

It sounds like you are trying to perform calculations related to Romer's determination of the speed of light. this link will give you an explanation of what Romer did to calculate the speed of light using the orbit of Io arouhd Jupiter. To answer your question, the earth observer views the event as it happened 54 minutes ago, at that distance. There is no lag caused by any eclipse or like phenomena because the light is not put "on hold" in the case of an eclipse, it is simply blocked. If Jupiter is 54 light-minutes away, then the observer sees events 54 minutes after they happened, and the observer does not view the event 108 minutes after the fact. Hope this helps.

• Hey Mr Cingoranelli yes I am hoping that perhaps you are interested in the reasoning and constructive discussion concerning the constant.because the dark is instantaneous but the light is not. So each time it reappears it starts a new moment 54 minutes in the past.Kind of like what happens to our moon we do not see the light carrier wave of information in till the reflected light off the moon from the sun returns after the earth blocks the light.that travels from the sun. right? thanks for your interest @rustnorm twitter – Apprentice DR NormanERustJR. Nov 30 '18 at 4:50
• Because dark is the absence of light, dark is not instantaneous. If the travel of light from Jupiter to Earth is stopped, light will still be received from Jupiter for 54 minutes. – Dominic Cingoranelli Dec 18 '18 at 3:31
• if I had a powerful laser pointed it at the moon after the light is there i shut it off for a 1/4 of a second then turn it back on. There is noway that "roughly"46,000 miles of dark is following light to the moon followed by the light I turned back on see published work at @rustnorm twitter – Apprentice DR NormanERustJR. Dec 18 '18 at 18:13
• I just had another follow up thought light is a carrier wave of present information once it has arrived to be observed and perhaps we a discussing spooky action at a distance aka quantum mechanics. I shall look forward to future interest hopefully lets enjoy the wonderment – Apprentice DR NormanERustJR. Dec 18 '18 at 18:20