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Posted to the UseNet Newsgroup "alt.astronomy" "SELENE" Thousands of years ago in ancient Greece, the Moon was called "Selene". And Selene was considered to be one of the seven wanderers in the sky (in ancient Greece, "wanderer" was pronounced "planet"). The wanderers were lights in the sky that moved or "wandered" around against the backdrop of fixed stars. We now know these seven wanderers/planets by the following names... the Sun Mercury Venus the Moon Mars Jupiter Saturn So for thousands of years, even up into modern times, the Moon was believed to be, not a satellite of Earth, but a full- fledged planet. It was only when Galileo first saw the four large moons of Jupiter through his nifty, new telescope that our Moon's status as a planet began to come into question. Since other planets had moons going around them, then the Moon must also just be a satellite going around us. So Selene/Luna was then seen as no longer a planet, but just a natural satellite of Earth. And compared with the length of time that the Moon was called a planet, it was not all that long ago! While he was still alive, Isaac Asimov thought that it was high time to restore the Moon's planet classification. And i agree that Asimov was right! So i am dedicating these articles to one of the greatest writers who ever lived, prolific author of both fiction *and* non-fiction science books and essays, and much, much more... I S A A C A S I M O V http://www.cenara.com/users/ce00018/nonfic.htm Please do keep in mind that there are several reasons for reclassifying the Moon as a major planet, and that many of these reasons will overlap and be intimately connected with each other. While some of the reasons by themselves on their own might seem weak (or strong), please wait until you've seen all the reasons before you decide. The idea of our Moon actually being a major planet was once proposed by Isaac Asimov, and he makes some very strong arguments, as you will see when all these reasons are added together... 1st Reason: The sizes of satellites relative to their primary planets are normally very, very small. The size (specially the diameter) of the Moon as compared with most other satellites, and more particularly the Moon's size relative to the size of Earth, is quite a bit larger than you would expect just a mere satellite to be. The Moon is huge. The only satellites bigger than the Moon are Jupiter's Ganymede, Callisto, and Io, and Saturn's biggest satellite, Titan. Even these four great satellites, however, are very, very tiny when compared to the planets they orbit. Our Moon's diameter is 3,475 kilometers (2,160 miles). That's a wee bit bigger than 1/4 the diameter of planet Earth. If Ganymede, Jupiter's largest-diameter satellite, wanted to compare in size to Jupiter as our Moon compares to Earth, Ganymede would have to grow to 7 1/2 times its present size! You could argue that the Moon is only 1/4 the diameter of Earth, has only 3/5 of Earth's density, only 1/50 of Earth's volume, is only 1/80 the mass of the Earth, sports only 1/6 of Earth's gravity, and has an escape velocity about 1/5 of Earth's. One might think that the two members of a double-planet system should be more like each other. And you just might be right... Jeff Root's Earth/Moon Comparison Page http://www.freemars.org/jeff/planets/Luna/Luna.htm And yet size, both compared with Earth and with most of the other companions of the planets, size isn't the *only* reason for reclassifying the Moon to "major planet" status. Another reason is because of where the "barycenter" is found. A barycenter is a term used by astronomers to describe the "center of gravity" of a system. And we'll touch on that next. happy days and... starry starry nights! -- Indelibly yours, Paine P.S. Thank YOU for reading! P.P.S. Some secret sites (shh)... http://painellsworth.net http://savethechildren.org http://eBook-eDen.secretsgolden.com |