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Distance from the earth to the moon
Roughly how long have astronomers been able to calculate the distance
between the earth and the moon with a reasonable degree of accuracy? I have briefly rooted around the internet for an answer, but have not been able find one. It's been a long time since I took physics. |
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Distance from the earth to the moon
catzz66 wrote:
Roughly how long have astronomers been able to calculate the distance between the earth and the moon with a reasonable degree of accuracy? I have briefly rooted around the internet for an answer, but have not been able find one. It's been a long time since I took physics. You're going to have to define "reasonable degree of accuracy" to have a reasonable answer. The rough distance has been known for thousands of years. Post Apollo we can measure it to less than a foot. In between is more or less a continuum. -- Greg Crinklaw Astronomical Software Developer Cloudcroft, New Mexico, USA (33N, 106W, 2700m) SkyTools: http://www.skyhound.com/cs.html Observing: http://www.skyhound.com/sh/skyhound.html Comets: http://comets.skyhound.com To reply take out your eye |
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Distance from the earth to the moon
"catzz66" wrote in message
Roughly how long have astronomers been able to calculate the distance between the earth and the moon with a reasonable degree of accuracy? I have briefly rooted around the internet for an answer, but have not been able find one. It's been a long time since I took physics. That would depend upon what you consider to be a reasonable degree of accuracy. In the modern era, radar signals bounced off of the Moon would have provided a pretty good fix prior to the installation of corner cube reflectors by the Apollo missions. Prior to both, triangulation with the width of the Earth as a base would have worked well. Newton had a pretty good idea of the distance. |
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Distance from the earth to the moon
On Jul 10, 9:54*am, catzz66 wrote:
Roughly how long have astronomers been able to calculate the distance between the earth and the moon with a reasonable degree of accuracy? *I have briefly rooted around the internet for an answer, but have not been able find one. *It's been a long time since I took physics. Hipparchus (190 B.C. -- 120 B.C.) correctly determined the moon's distance to be 30 times the diameter of the earth. (Using Eratosthene's (276 B.C. -- 196 B.C.) value for the earth's diameter that would have placed the moon approximately 250,000 miles away. That sounds pretty reasonable to me. So a plausible to answer to your question would be about 2,130 years. Aristarchus (310 B.C. -- 230 B.C.) measured the moon's distance earlier; but his results were far less accurate. My source (which also gives a brief explanation of how the measurements were made): "Asimov's Biographical Encyclopedia of Science & Technology" Bill Greer To sketch is to see. http://cejour.blogspot.com http://www.rangeweb.net/~sketcher |
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Distance from the earth to the moon
"catzz66" wrote in message ... Roughly how long have astronomers been able to calculate the distance between the earth and the moon with a reasonable degree of accuracy? I have briefly rooted around the internet for an answer, but have not been able find one. It's been a long time since I took physics. You live under a rock..right?? |
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Distance from the earth to the moon
Greg Crinklaw wrote:
catzz66 wrote: Roughly how long have astronomers been able to calculate the distance between the earth and the moon with a reasonable degree of accuracy? I have briefly rooted around the internet for an answer, but have not been able find one. It's been a long time since I took physics. You're going to have to define "reasonable degree of accuracy" to have a reasonable answer. The rough distance has been known for thousands of years. Post Apollo we can measure it to less than a foot. In between is more or less a continuum. How long the rough distance has been known is all I was really wondering about and "thousands of years" is close enough. Thanks for your reply and the others that followed. |
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Distance from the earth to the moon
"catzz66" wrote in message
Greg Crinklaw wrote: catzz66 wrote: Roughly how long have astronomers been able to calculate the distance between the earth and the moon with a reasonable degree of accuracy? I have briefly rooted around the internet for an answer, but have not been able find one. It's been a long time since I took physics. You're going to have to define "reasonable degree of accuracy" to have a reasonable answer. The rough distance has been known for thousands of years. Post Apollo we can measure it to less than a foot. In between is more or less a continuum. How long the rough distance has been known is all I was really wondering about and "thousands of years" is close enough. Thanks for your reply and the others that followed. The ancient Greeks did a credible job. Aristarchus (~300 BC) estimated the size of the Moon to be 1/4 that of the Earth by observations of the shadow of the Earth on the Moon. Around 200 BC Eratosthenes worked out the true size of the Earth using the angle of Sun rays at two locations. The distance then falls out by simple geometry. |
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Distance from the earth to the moon
In sci.astro.amateur message , Thu,
10 Jul 2008 10:54:16, catzz66 posted: Roughly how long have astronomers been able to calculate the distance between the earth and the moon with a reasonable degree of accuracy? That's an ambiguous question. If Pytheas had reported that, in a certain month, he had seen the Moon pass under a certain star, and if in Rome the Moon had been seen passing just over that star in that month, then, assuming the star to be relatively distant, the moon's diameter could have been known to be a little less than Pytheas' northward distance from Rome. But that's not the same as saying that anyone actually did that at the time. The same can be said for other sorts of observation, for example of the curvature of the Earth's shadow during a lunar eclipse. Additionally, is this to be restricted to astronomers in the western European tradition, or are Asiatic astronomers to be included? Only in comparatively recent times has it been safe to say that everything of interest has been measured to about the greatest accuracy possible at the time. -- (c) John Stockton, nr London, UK. Turnpike v6.05 MIME. Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links; Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc. No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News. |
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Distance from the earth to the moon
On 2008-07-10, catzz66 wrote:
Roughly how long have astronomers been able to calculate the distance between the earth and the moon with a reasonable degree of accuracy? I have briefly rooted around the internet for an answer, but have not been able find one. It's been a long time since I took physics. Aristarchus of Samos in 270 BC estimated the distance from the Earth to the Moon as 60 Earth radii. He did this by timing lunar eclipses. The mean radius of the Moon's orbit is about 60.3 Earth radii, making Aristarchus' estimate a pretty good result. Tycho measured the lunar parallax over the years, which is the same as measuring the earth-moon distance in terms of earth radii. His measurements supposedly were good to a couple of minute of arc. You had to use telescopic sights to get better measurements, and by the end of the 18th century astronomers had a good handle on the earth-moon distance. Bud |
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Distance from the earth to the moon
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