# Curve of the shadow on the Moon **URL:** \ **Category:** Factual Questions\ **Created:** [October 19, 2003, 11:26am UTC](https://boards.straightdope.com/t/curve-of-the-shadow-on-the-moon/208343 "2003-10-19T11:26:14Z")\ **Posts on this page:** 9\ **Page:** 2
**Author:** ![Freddy\_the\_Pig](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@Freddy\_the\_Pig](https://boards.straightdope.com/u/Freddy_the_Pig)\ **Post date:** [October 20, 2003, 4:16pm UTC](https://boards.straightdope.com/t/curve-of-the-shadow-on-the-moon/208343/21 "2003-10-20T16:16:33Z")
See [here](http://galileoandeinstein.physics.virginia.edu/lectures/gkastr1.html) for a good description of how the ancient Greeks used eclipses to estimate the distance to the Moon, and how they less successfully attempted to estimate the distance to the Sun. The quote in the OP, of course, is complete hogwash. The church in Magellan’s time did _not_ maintain that the Earth was flat. No educated person had maintained that since the time of the Greeks. ---
**Author:** ![FriendRob](https://avatars.discourse-cdn.com/v4/letter/f/ecc23a/32.png) [@FriendRob](https://boards.straightdope.com/u/FriendRob)\ **Post date:** [October 20, 2003, 5:10pm UTC](https://boards.straightdope.com/t/curve-of-the-shadow-on-the-moon/208343/22 "2003-10-20T17:10:06Z")
Well, this site [http://www.earlychurch.org.uk/creation\_flatearth.html](http://www.earlychurch.org.uk/creation_flatearth.html) has links to those who argue that the early church did/didn’t think the earth was flat. In particular [http://www.ethicalatheist.com/docs/flat\_earth\_myth\_ch2.html](http://www.ethicalatheist.com/docs/flat_earth_myth_ch2.html) lists seven early Christian writers who say (or imply?) that the earth is flat. It doesn’t give quotes, so who knows if these are “four corners of the earth” things that could be purely figures of speech, or actual statements/defenses of the flat earth. Even this site, which claims that the chruch-flat earth connection is incorrect, admits two early Christian writers defended the idea: [http://www.christiananswers.net/q-aig/aig-c034.html](http://www.christiananswers.net/q-aig/aig-c034.html) From a quick glance over these sites, it seems clear that 1. up until the 6th century AD there were several opinions on the matter, and no official Church view. 2. after that time, the spherical earth is universal (among educated writers, at least - who knows what the average-slob-in-the-street thought) 3. there was an effort in the 19th century to tar the Church with the flat-earth brush 4. that modern Christians go the other direction, and downplay evidence of flat-earth thinking among early Christians, calling it a myth invented by anti-Church forces. Can anyone define _objectivity_ for me, class? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 20, 2003, 7:36pm UTC](https://boards.straightdope.com/t/curve-of-the-shadow-on-the-moon/208343/23 "2003-10-20T19:36:37Z")
> [@](#): > > You just need to know the angular (apparent) size of the sun as seen from the earth, which you can measure by simply looking up. That angle is equal to the angle between the edge of the umbra and the edge of the penumbra. Which doesn’t help you. All that gives you is the ratio of the Moon’s diameter to its distance, which again, is much easier to find from just observing its angular size. But you can measure the distance to the Moon fairly accurately using parallax, from different points of observation on the Earth. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [October 20, 2003, 11:33pm UTC](https://boards.straightdope.com/t/curve-of-the-shadow-on-the-moon/208343/24 "2003-10-20T23:33:42Z")
> [@](#): > > \*Originally posted by FriendRob \* > \*\* > 4) that modern Christians go the other direction, and downplay evidence of flat-earth thinking among early Christians, calling it a myth invented by anti-Church forces. > > Can anyone define _objectivity_ for me, class? \*\* I’ve seen modern folk that exhibit flat-earth thinking, so I dunno why that’s such a surprise. ---
**Author:** ![CurtC](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@CurtC](https://boards.straightdope.com/u/CurtC)\ **Post date:** [October 21, 2003, 1:14am UTC](https://boards.straightdope.com/t/curve-of-the-shadow-on-the-moon/208343/25 "2003-10-21T01:14:58Z")
> [@](#): > > _Chronos wrote:_ > Which doesn’t help you. All that gives you is the ratio of the Moon’s diameter to its distance, which again, is much easier to find from just observing its angular size. jklann posted a nice link explaining how to use the Earth’s penumbra to get a fairly accurate measure of the Moon’s distance. This technique works for an observer in just one location. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [October 21, 2003, 1:45am UTC](https://boards.straightdope.com/t/curve-of-the-shadow-on-the-moon/208343/26 "2003-10-21T01:45:23Z")
> [@](#): > > \*Originally posted by RM Mentock \* > \*\*0, 1, 2, or 3 according to [Mr. Eclipse](http://www.mreclipse.com/Special/LEprimer.html) \*\* You can only get that result by excluding penumbral eclipses. Of course, a penumbral eclipse isn’t going to demonstrate the effect the OP was talking about, but it’s still an eclipse. ---
**Author:** ![Shortie](https://avatars.discourse-cdn.com/v4/letter/s/ecd19e/32.png) [@Shortie](https://boards.straightdope.com/u/Shortie)\ **Post date:** [October 21, 2003, 10:23am UTC](https://boards.straightdope.com/t/curve-of-the-shadow-on-the-moon/208343/27 "2003-10-21T10:23:42Z")
Okay, so the quote is probably made up, which is a shame. Google couldn’t give me a decent cite, nor do any really reputable sites have it. But you’re telling me the concept does work, which is nice. And thata not only is it a lot older than I thought, but that lunar eclipses are a lot more common than I thought. Hey ho. (I’m not interested in the whole religion angle, I’d just like a nice answer to anyone who says that you can’t prove the Earth is a sphere without going up into orbit, or flying around it, or whatever). So thanks all. I’ll have to try it for myself. ---
**Author:** ![RM\_Mentock](https://avatars.discourse-cdn.com/v4/letter/r/e274bd/32.png) [@RM\_Mentock](https://boards.straightdope.com/u/RM_Mentock)\ **Post date:** [October 21, 2003, 10:47am UTC](https://boards.straightdope.com/t/curve-of-the-shadow-on-the-moon/208343/28 "2003-10-21T10:47:26Z")
Next lunar eclipse, Nov. 9, and it’s early evening (USA) ---
**Author:** ![commasense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/commasense/32/3017_2.png) [@commasense](https://boards.straightdope.com/u/commasense)\ **Post date:** [October 21, 2003, 2:28pm UTC](https://boards.straightdope.com/t/curve-of-the-shadow-on-the-moon/208343/29 "2003-10-21T14:28:14Z")
I’m reminded of a bit Steve Martin did called “What I Believe,” which included\* this: “I believe that a total eclipse of the sun is a beautiful and moving experience, but an eclipse of the moon is a cheap and degrading spectacle.” - As I recall it, at least. Several Web sources on the sketch don’t include this one, which I think is the best of the lot. Well, if he doesn’t take credit for it, I will. [Previous page](https://boards.straightdope.com/t/curve-of-the-shadow-on-the-moon/208343.md?page=1)