# When in its orbit is the Moon visible to the fewest number of people on Earth? **URL:** \ **Category:** Factual Questions\ **Created:** [September 9, 2014, 4:26am UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931 "2014-09-09T04:26:58Z")\ **Posts on this page:** 12\ **Page:** 2
**Author:** ![Skald\_the\_Rhymer](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Skald\_the\_Rhymer](https://boards.straightdope.com/u/Skald_the_Rhymer)\ **Post date:** [September 10, 2014, 9:14pm UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931/21 "2014-09-10T21:14:49Z")
> [@Chronos](#): > > Incidentally, it really isn’t at all remarkable for the Moon to be visible in the daytime. At any given phase other than completely new or completely full, it’s possible for at least part of the day-night cycle, and overall, it’s visible about half the time, day or night. It is surprisingly difficult to persuade some people of this fact, though you’d think it would be trivially easy. I blame Genesis. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [September 10, 2014, 10:37pm UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931/22 "2014-09-10T22:37:39Z")
> [@Skald\_the\_Rhymer](#): > > It is surprisingly difficult to persuade some people of this fact, though you’d think it would be trivially easy. I blame Genesis. Yeah. The remarkable part isn’t that the Moon is visible during the day–that much is obvious to anyone with a 3rd-grade understanding of the solar system–it’s that so many people fail to appreciate the fact. Do people simply not look _up_ from time to time? Is the Moon like those apocryphal sailing ships that were “invisible” to the ignorant natives? I couldn’t say. ---
**Author:** ![Greg\_Charles](https://avatars.discourse-cdn.com/v4/letter/g/839c29/32.png) [@Greg\_Charles](https://boards.straightdope.com/u/Greg_Charles)\ **Post date:** [September 10, 2014, 11:01pm UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931/23 "2014-09-10T23:01:20Z")
> [@Chronos](#): > > And given that it’s visible to a hemisphere, the answer to the OP’s question is simply the antipode to the answer to that question. > > Though it’s not a point in its orbit in either case, so much as an orientation of the Earth under it. You’re saying the point where the moon is visible to the least number of people is the antipode to the point where it is visible to most people? I don’t think that’s a logical conclusion. I love the link in the XKCD article to the highly dangerous, but available to anyone with $300 (now $349), [1 watt laser](http://www.wickedlasers.com/arctic). It has a disclaimer that it is not a toy. OK, I guess its resemblance to a light saber is purely unintentional. ---
**Author:** ![Greg\_Charles](https://avatars.discourse-cdn.com/v4/letter/g/839c29/32.png) [@Greg\_Charles](https://boards.straightdope.com/u/Greg_Charles)\ **Post date:** [September 10, 2014, 11:10pm UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931/24 "2014-09-10T23:10:00Z")
OK, on consideration, I take that back. If the moon really is visible to exactly half the globe, then the antipodal thing makes sense. Sorry about that. Carry on! ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [September 10, 2014, 11:16pm UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931/25 "2014-09-10T23:16:16Z")
[QUOTE=John DiFool] When it is new, and dark, and lost in the glare of the sun? Or perhaps I am misunderstanding the question… [/quote] > [@Mangetout](#): > > I think the OP is going for the position in the moon’s orbit where the smallest number of people have theoretical line of sight, rather than ‘smallest number of people who notice, or bother looking’ Actually John DiFool has given a very good answer. There is a period of about 30 hours every month when no-one on Earth can see the Moon, even with a very good telescole, because of the glare of the Sun. This website gives data on when the Moon will become visible again after the next New Moon; this data is interesting for observers, some of whom try to see it when it is very small, and useful for Muslims, who use the first sighting to calculate their calendar; [http://astro.ukho.gov.uk/moonwatch/nextnewmoon.html](http://astro.ukho.gov.uk/moonwatch/nextnewmoon.html) ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [September 10, 2014, 11:43pm UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931/26 "2014-09-10T23:43:32Z")
> [@eburacum45](#): > > There is a period of about 30 hours every month when no-one on Earth can see the Moon, even with a very good telescole, because of the glare of the Sun. This is certainly mostly true, but I wonder if it’s 100% true. Someone above the atmosphere should be able to see a new Moon; it will have strong Earthshine (since someone on the Moon would see a “full Earth”), and it should be possible to block all glare from the Sun. Too much atmosphere makes this impossible, but I wonder if a high mountain peak would be above just enough air to make it work. Pressure at the top of Everest is 1/3 that at sea level. Might be enough. ---
**Author:** ![wevets](https://avatars.discourse-cdn.com/v4/letter/w/e9a140/32.png) [@wevets](https://boards.straightdope.com/u/wevets)\ **Post date:** [September 10, 2014, 11:52pm UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931/27 "2014-09-10T23:52:14Z")
> [@Skald\_the\_Rhymer](#): > > I blame Genesis. The band or the Star Trek MacGuffin? ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [September 11, 2014, 12:45am UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931/28 "2014-09-11T00:45:27Z")
> [@Dr.Strangelove](#): > > Someone above the atmosphere should be able to see a new Moon; it will have strong Earthshine (since someone on the Moon would see a “full Earth”), and it should be possible to block all glare from the Sun. I expect someone on the ISS could block the Sun sufficiently well to see the Moon most of the time, although the OP did specify on Earth. > [@](#): > > Too much atmosphere makes this impossible, but I wonder if a high mountain peak would be above just enough air to make it work. Pressure at the top of Everest is 1/3 that at sea level. Might be enough. This would only reduce the invisibility period by a calculable fraction, not remove it altogether. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [September 11, 2014, 1:19am UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931/29 "2014-09-11T01:19:45Z")
Here’s an image of the New Moon, only 3 hours 27 minutes old; [http://the-moon.wikispaces.com/LPOD+Jan+31%2C+2008](http://the-moon.wikispaces.com/LPOD+Jan+31%2C+2008) as Dr Strangelove expected, it was taken from a mountain; to reduce glare from the sky even further, it was taken in the infrared. ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [September 11, 2014, 4:11am UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931/30 "2014-09-11T04:11:34Z")
> [@eburacum45](#): > > …There is a period of about 30 hours every month when no-one on Earth can see the Moon, even with a very good telescole, because of the glare of the Sun… Where can I get a very good telescole, anyway? ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [September 11, 2014, 6:57am UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931/31 "2014-09-11T06:57:40Z")
> [@eburacum45](#): > > Actually John DiFool has given a very good answer. There is a period of about 30 hours every month when no-one on Earth can see the Moon, even with a very good telescole, because of the glare of the Sun. Except, I don’t believe that’s what the OP was asking for, given that he frames the question in terms of angles and populations. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [September 11, 2014, 7:15am UTC](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931/32 "2014-09-11T07:15:41Z")
> [@Greg\_Charles](#): > > You’re saying the point where the moon is visible to the least number of people is the antipode to the point where it is visible to most people? I don’t think that’s a logical conclusion. > [@Greg\_Charles](#): > > OK, on consideration, I take that back. If the moon really is visible to exactly half the globe, then the antipodal thing makes sense. Sorry about that. Carry on! I went through the exact same thought process as you, except that I haven’t quite convinced myself of the second part (although all my clever thought experiments to try to find an exception have failed). However, I think that bit of the question deserves its own [thread](http://boards.straightdope.com/sdmb/showthread.php?t=733818). [Previous page](https://boards.straightdope.com/t/when-in-its-orbit-is-the-moon-visible-to-the-fewest-number-of-people-on-earth/697931.md?page=1)