# What Is The Maximum Possible Length Of Eclipse Totality? **URL:** \ **Category:** Factual Questions\ **Created:** [August 22, 2017, 6:59pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393 "2017-08-22T18:59:42Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![HeyHomie](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/heyhomie/32/207_2.png) [@HeyHomie](https://boards.straightdope.com/u/HeyHomie)\ **Post date:** [August 22, 2017, 6:59pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/1 "2017-08-22T18:59:42Z")
Given optimal placement of the moon, sun, earth, and observer, and if everything works out perfectly, how long could an observer expect to see totality? I don’t mean in any specific eclipse, but in a hypothetical (but possible) “perfect” eclipse? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [August 22, 2017, 7:01pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/2 "2017-08-22T19:01:18Z")
7 minutes 29 seconds. > **[Solar eclipse of July 16, 2186](https://en.m.wikipedia.org/wiki/Solar_eclipse_of_July_16,_2186)** > > A total solar eclipse will occur on July 16, 2186, which will be the longest total eclipse for thousands of years. The eclipse will pass over the southern Galápagos Islands (with a total eclipse of 4 minutes occurring over the southern tip of Española Island), the northern tip of Ecuador (with a total eclipse of 3 minutes and 26 seconds on Isla Santa Rosa), central Colombia (4 minutes and 50 seconds over Bogota), central Venezuela, and northern Guyana (7 minutes and 4 seconds just north of Anna R... ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [August 22, 2017, 7:07pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/3 "2017-08-22T19:07:08Z")
> [@beowulff](#): > > 7 minutes 29 seconds. > [Solar eclipse of July 16, 2186 - Wikipedia](https://en.m.wikipedia.org/wiki/Solar_eclipse_of_July_16,_2186) From your link: > [@Wikipedia](#): > > The longest eclipse theoretically possible for the 3rd millennium is 7 minutes and 32 seconds. Of course that ignores the missing chunk of moon that will be blasted away on the Eastern Limb during the Great Moon War of 2874. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [August 22, 2017, 7:32pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/4 "2017-08-22T19:32:23Z")
The “hypothetical perfect eclipse” duration is calculated assuming the Earth is exactly at aphelion and the moon is at perigee; this is where the value of 7m 32s comes from. The funny thing about such a calculation is that we can compute the circumstances of all _actual_ eclipses, so what does it really mean? At least it tells us how close we get to perfect conditions, and the answer is pretty close (but rarely achieved, so if you missed the last long eclipse in 744 BC, you have another chance in 2186— 2168 and 2204 are almost as good— but after that you should not hold your breath). ---
**Author:** ![Dewey\_Finn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dewey_finn/32/4222_2.png) [@Dewey\_Finn](https://boards.straightdope.com/u/Dewey_Finn)\ **Post date:** [August 22, 2017, 7:35pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/5 "2017-08-22T19:35:09Z")
> [@beowulff](#): > > 7 minutes 29 seconds. > [Solar eclipse of July 16, 2186 - Wikipedia](https://en.m.wikipedia.org/wiki/Solar_eclipse_of_July_16,_2186) I’m booking my hotel room now. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [August 22, 2017, 8:31pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/6 "2017-08-22T20:31:57Z")
\ Over 70 minutes, if you happen to have a Concorde handy {[Cite](https://motherboard.vice.com/en_us/article/8q8qwk/the-concorde-and-the-longest-solar-eclipse)} … \ ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [August 22, 2017, 8:40pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/7 "2017-08-22T20:40:10Z")
Note that the moon is slowly receding from the earth, so eclipses are getting shorter and will eventually become impossible. Imagine when the moon was only a tenth as far away as it is now. ---
**Author:** ![Mangosteen](https://avatars.discourse-cdn.com/v4/letter/m/6a8cbe/32.png) [@Mangosteen](https://boards.straightdope.com/u/Mangosteen)\ **Post date:** [August 22, 2017, 8:58pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/8 "2017-08-22T20:58:39Z")
I was fortunate to see a 6 minute 53 second total solar eclipse in Hawaii in 1991, but was spoiled by it. It is probably the longest one anybody will ever see in our life times. When I saw that the max for the latest one was around 2 and a half minutes, I said “pass”, not worth the drive. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [August 22, 2017, 9:41pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/9 "2017-08-22T21:41:46Z")
> [@Dewey\_Finn](#): > > I’m booking my hotel room now. If you want alternative locations, [the complete path.](https://eclipse.gsfc.nasa.gov/5MCSEmap/2901-3000/2903-07-16.gif) ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [August 22, 2017, 10:10pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/10 "2017-08-22T22:10:08Z")
Alternative locations in the middle of the ocean ? Anyway, that’s over 7 minutes, sure, but too little and 700 years too late after [the ultimate eclipse](https://www.eclipsewise.com/solar/SEping/2101-2200/SE2186-07-16T.gif). ---
**Author:** ![SCSimmons](https://avatars.discourse-cdn.com/v4/letter/s/e495f1/32.png) [@SCSimmons](https://boards.straightdope.com/u/SCSimmons)\ **Post date:** [August 23, 2017, 5:14am UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/11 "2017-08-23T05:14:28Z")
Well, if we’re looking at hypotheticals, just tow the Moon into a geostationary orbit exactly in the plane of the Earth’s orbit around the Sun. Then someplace gets eclipsed for an arbitrarily long period. I guess you need to untilt the Earth’s plane of rotation relative to its orbit as well. No more seasons, nor tides. Small price to pay, though, right? (Ooh, does DC accept freelance story writing for _Superman_?) ---
**Author:** ![SCSimmons](https://avatars.discourse-cdn.com/v4/letter/s/e495f1/32.png) [@SCSimmons](https://boards.straightdope.com/u/SCSimmons)\ **Post date:** [August 23, 2017, 5:24am UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/12 "2017-08-23T05:24:14Z")
Actually, you need a 48 hour orbit, so the Moon matches the Sun moving across the sky. So you’ll have an eternal eclipse speeding around the equator once per day. And with the Moon that close, tides will be ridiculous … ---
**Author:** ![SCSimmons](https://avatars.discourse-cdn.com/v4/letter/s/e495f1/32.png) [@SCSimmons](https://boards.straightdope.com/u/SCSimmons)\ **Post date:** [August 23, 2017, 5:28am UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/13 "2017-08-23T05:28:53Z")
Dang, that’s _still_ not right. You basically need to put the Moon at the solar L1 Lagrange point; but that’s too far from the Earth for it to eclipse the sun. We’re going to need a bigger moon … ---
**Author:** ![standingwave](https://avatars.discourse-cdn.com/v4/letter/s/9de0a6/32.png) [@standingwave](https://boards.straightdope.com/u/standingwave)\ **Post date:** [August 23, 2017, 5:36am UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/14 "2017-08-23T05:36:42Z")
> [@HeyHomie](#): > > Given optimal placement of the moon, sun, earth, and observer, and if everything works out perfectly, how long could an observer expect to see totality? I don’t mean in any specific eclipse, but in a hypothetical (but possible) “perfect” eclipse? A friend of mine saw the 1991 eclipse from La Paz which was pretty close to the point of maximum eclipse where the duration would have been 6m53s. He was part of our group in Oregon yesterday and said the La Paz experience kinda spoiled him for anything shorter. 2m8s just can’t compare. > **[Solar eclipse of July 11, 1991](https://en.wikipedia.org/wiki/Solar_eclipse_of_July_11,_1991#/media/File:SE1991Jul11T.png)** > > A total solar eclipse occurred at the Moon’s descending node of the orbit on Thursday, July 11, 1991. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a... ---
**Author:** ![Saffer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saffer/32/6440_2.png) [@Saffer](https://boards.straightdope.com/u/Saffer)\ **Post date:** [August 23, 2017, 9:15am UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/15 "2017-08-23T09:15:59Z")
L1 is unstable, so for that reason alone, this option is not practical. Sent from my iPhone using Tapatalk ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [August 23, 2017, 1:42pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/16 "2017-08-23T13:42:53Z")
Once we’re moving the Moon there, we can use the same propulsion system for indefinite station-keeping. The relatively hard part is getting there, not staying there. ---
**Author:** ![zimaane](https://avatars.discourse-cdn.com/v4/letter/z/a3d4f5/32.png) [@zimaane](https://boards.straightdope.com/u/zimaane)\ **Post date:** [August 23, 2017, 4:51pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/17 "2017-08-23T16:51:24Z")
At the other end of the scale, the 1912 eclipse featured a totality of _two seconds_. [Solar eclipse of April 17, 1912 - Wikipedia](https://en.wikipedia.org/wiki/Solar_eclipse_of_April_17,_1912) ---
**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:** [August 23, 2017, 5:36pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/18 "2017-08-23T17:36:33Z")
If we’re allowing _any_ viewing location, then you can get a two-week eclipse. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [August 23, 2017, 6:07pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/19 "2017-08-23T18:07:47Z")
Assuming your _any_ is limited to Earth and Moon, is that an “eclipse” or is that a “night”? And if you didn’t mean to be limited to those two I’d be curious to know where you’re talking about. e.g. Saturn occulting the Sun from Titan’s POV or whatever. Not that I doubt you; the point is there’s all sorts of fun possibilities out there with all the various layers of orbiting bodies. ---
**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:** [August 23, 2017, 6:37pm UTC](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393/20 "2017-08-23T18:37:40Z")
That’s a viewing location on the Moon, with “eclipse” having its usual meaning of “the Sun being blocked by the Moon”. [Next page](https://boards.straightdope.com/t/what-is-the-maximum-possible-length-of-eclipse-totality/794393.md?page=2)