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Q: science in the 1700-1800's ( Answered,   1 Comment )
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 Subject: science in the 1700-1800's Category: Science Asked by: lawnmowerman1067-ga List Price: \$2.00 Posted: 14 Jan 2003 14:02 PST Expires: 13 Feb 2003 14:02 PST Question ID: 142670
 ```in the 1700's and 1800's how did they find the distance to the moon,and the mass of the earth```
 ```Hi, You don't have to wait until 16th century to estimate the distance to moon. According to a NASA site: http://www-istp.gsfc.nasa.gov/stargaze/Shipprc2.htm Aristarchus around 270 BC derived the Moon's distance from the duration of a lunar eclipse (Hipparchus later improved that method). His argument, in a nutshell: if the Moon circles the Earth, then in about a month it completes a full orbit, the length of which (assuming it is a circle) is about 6 times the distance of the Moon. For the question of the mass of earth, we have to come to the Newton's age. Isaac Newton showed that the gravitational acceleration "g" experienced by an object caused by the gravitational attraction of a second body, is directly proportional to the mass "M" of the attracting body, and inversely proportional to the square of the distance "R" between the two bodies. g = (G * M) / (R * R) Here, G denotes the gravitational constant. once G is known the mass of the Earth can be obtained from the 9.8 m/s2 gravitational acceleration on the Earth surface. G was first measured in the laboratory; in 1798 by Cavendish and co-workers accurate to about 1%. More information can be found at: http://www.npl.washington.edu/eotwash/gconst.html Bonus: Using this information, the Sun's mass can also be obtained from the size and period of the Earth orbit around the sun. Hope this helps Regards Bio Google Answers Researcher```
 ```Bio's right, but if you're interested in 16th century astronomy the answer's parallax - you measure the position of the moon against the stars, simultaneously, from widely separated positions on Earth. Knowing the distance between your observing points you can work out the distance to the moon. Ian G.```