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martyb [soylentnews.org] writes:

Grab Some Binoculars and go Look at Jupiter Tonight [cnet.com]:

Jupiter will reach opposition on Monday, June 10 in an annual event that marks the time when Earth is directly between the gas giant and the sun. This means Jupiter is fairly close to Earth and you can spot it lurking in the sky all night long. This entire month offers up great viewing opportunities.

"The solar system's largest planet is a brilliant jewel to the naked eye, but looks fantastic through binoculars or a small telescope, which will allow you to spot the four largest moons, and maybe even glimpse a hint of the banded clouds that encircle the planet," NASA suggests in a skywatching update for June.

According to Wikipedia [wikipedia.org]:

When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough for its reflected light to cast shadows, and making it on average the third-brightest natural object in the night sky after the Moon and Venus.

[...]Jupiter has 79 known moons, including the four large Galilean moons discovered by Galileo Galilei in 1610. Ganymede, the largest of these, has a diameter greater than that of the planet Mercury.

[...]Jupiter's diameter is one order of magnitude smaller (×0.10045) than that of the Sun, and one order of magnitude larger (×10.9733) than that of Earth. The Great Red Spot is roughly the same size as Earth.

Fun Fact: Jupiter played a part in the first measurement of the speed of light [amnh.org]!

In 1676, the Danish astronomer Ole Roemer (1644–1710) became the first person to measure the speed of light. Until that time, scientists assumed that the speed of light was either too fast to measure or infinite. The dominant view, vigorously argued by the French philosopher Descartes, favored an infinite speed.

[...]The orbital period of Io is now known to be 1.769 Earth days. The satellite is eclipsed by Jupiter once every orbit, as seen from the Earth. By timing these eclipses over many years, Roemer noticed something peculiar. The time interval between successive eclipses became steadily shorter as the Earth in its orbit moved toward Jupiter and became steadily longer as the Earth moved away from Jupiter. These differences accumulated. From his data, Roemer estimated that when the Earth was nearest to Jupiter (at E1), eclipses of Io would occur about eleven minutes earlier than predicted based on the average orbital period over many years. And 6.5 months later, when the Earth was farthest from Jupiter (at E2), the eclipses would occur about eleven minutes later than predicted.

Roemer knew that the true orbital period of Io could have nothing to do with the relative positions of the Earth and Jupiter. In a brilliant insight, he realized that the time difference must be due to the finite speed of light. That is, light from the Jupiter system has to travel farther to reach the Earth when the two planets are on opposite sides of the Sun than when they are closer together. Romer estimated that light required twenty-two minutes to cross the diameter of the Earth’s orbit. The speed of light could then be found by dividing the diameter of the Earth’s orbit by the time difference.

The first calculated speed of light was 131,000 mph; within 30 percent of the accepted speed of 186,000 mph. It was a result of errors in the measured time difference and in the estimated the size of Earth's orbit. To get an idea of how momentous that calculation was, take a look at the history [wikipedia.org] behind prior attempts to determine if light had a fixed speed and, if it did, what it was.

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