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The ancients only knew about (5 planets + Earth) because to really see the other two you needed a telescope. The planets they knew were:

# Mercury # Venus # (Earth) # Mars # Jupiter # Saturn All these are easily visible to the naked eye and of cause they can be seen to move against the background of the stars (except the Earth because we are on that)

It was in 1718 (290 years ago) that Uranus the 7th planet was discovered by William Herschel using a telescope. Although it is visible to the naked eye like the other six, it was never recognized as a planet by ancient observers due to its dimness and slow orbit. The 8th planet Neptune was found by mathematical prediction rather than regular observation. Unexpected changes in the orbit of Uranus led astronomers to deduce the gravitational perturbation of an unknown planet was the cause and they predicted where to look to find it.

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โˆ™ 2008-06-14 00:51:10
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Q: Why did ancient civilizations only know about six planets?
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Related questions

How did ancient scientists know that there are nine planets in the solar system without having any special equipment?

Ancient astrologers only knew about 5 planets plus Earth. They knew about the 5 planets from visual observation.Furthermore, there are only 8 planets in our solar system.

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Ptolemy only knew 5 planets other than the Earth:MercuryVenusMarsJupiterSaturnThe reason is that these planets are visible with the naked eye. Also, keep in mind that most people in the ancient world didn't know that the Earth was a planet.

How did ancient India discover 7 planets without a telescope?

Ancient India discovered only 5 planets without a telescope, because they could see the planets with their eyes, just as we can. Those planets are:MercuryVenusMarsJupiterSaturn

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Earth is the only planet NOT named after a god.

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during the ancient times river was the only source of water for the people. so they settled near around the river only. the civilizations that flourished in the river valleys are called river valley civilization.

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As far as we know, only Planet Earth. There may be another planet that we don't know of though.

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In nothing. These ancient civilizations (Mayans, Aztecs) were completely wiped out by the invading armies of Spanish conquistadors. They only contributed during colonial times in the form of slave labor, but by 1550 most of them were dead or being assimilated into the larger population.