It has to do with the amount of time it takes the the light from the moon of Jupiter to reach the earth depending on if the earth is on the same side of the sun as Jupiter compared to the opposite side of the sun from Jupiter. Because of the time difference for the light to arrive, the orbit of the moons appear late in passing behind or in front of Jupiter when earth is on the opposite side of the sun from Jupiter, compared to when it is on the same side. This time difference is then the time it takes the light to travel the diameter of the earth's orbit around the sun. Velocity is then simply distance divided by time.
Of course you still need to know how to calculate the diameter of the earth's orbit around the sun in the 17th century, but that's another answer!
Look up the astronomer named Ole Christensen Rømer he was the one who noticed this first, his estimate was 11 minutes difference, and resulted in a figure of 130,000 miles per second. 186,300 miles per second or 299,792 km per second is the actual speed.
Are you asking when the speed of light was first estimated, or are you asking when the speed of light was first actually measured?
Jupiter and its moons get light from the same source we do: the sun.
The first person to prove that light does not travel at infinite speed was Danish astronomer Ole Rømer in the 17th century. He observed the moons of Jupiter and noted discrepancies in their predicted and observed timings, which led him to the conclusion that light takes time to travel from one place to another.
The luminous light source in the solar system that illuminates Jupiter's moons, including when light bounces off them, is the Sun. Jupiter and its moons receive sunlight, which provides the illumination observed from Earth.
It doesn't reflect, it goes straight there.
By Roemer, observing the moons of Jupiter.
Are you asking when the speed of light was first estimated, or are you asking when the speed of light was first actually measured?
An early measurement was done by Ole Rømer, by observing Jupiter's moons.
One of the earliest measurements was made by observing the orbits of the moons of Jupiter.
It shines directly on both Jupiter and its moons. There is no reason it shouldn't, as, other than periodic eclipses from Jupiter, nothing blocks the sunlight from reaching those moons. The moons do get some reflected light from Jupiter as well, just as Earth gets some light from our moon.
The first estimation of the speed of light was based on observing the timing differences between the eclipses of Jupiter's moons as observed from Earth. This was done by Ole Rømer in 1676.
Jupiter and its moons get light from the same source we do: the sun.
The moons of Jupiter can be observed using a telescope, even a small one, as they are relatively bright and large compared to other celestial objects. The four largest moons, known as the Galilean moons (Io, Europa, Ganymede, and Callisto), were discovered by Galileo Galilei in 1610 and can be seen as small points of light near Jupiter. Binoculars can also provide a view of these moons, although details will be limited. For the best experience, observing during a clear night with minimal light pollution is recommended.
The first person to prove that light does not travel at infinite speed was Danish astronomer Ole Rømer in the 17th century. He observed the moons of Jupiter and noted discrepancies in their predicted and observed timings, which led him to the conclusion that light takes time to travel from one place to another.
No, Jupiter's moons do not have phases like Earth's moon. Phases are caused by the changing positions of the sun, Earth, and moon, but Jupiter's moons have no light of their own and do not reflect sunlight in the same way.
The best telescope for observing Jupiter's moons is a high-quality refractor or reflector telescope with a large aperture, such as a 6-inch or larger telescope. These telescopes provide clear and detailed views of Jupiter and its moons, allowing you to see features like the Galilean moons and their orbits around the planet.
Jupiter's moons do not have moons. No moon in the Solar System has a moon orbiting it.