# What Is The Maximum Possible Length Of Eclipse Totality?

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?

7 minutes 29 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.

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).

I’m booking my hotel room now.

<snark> Over 70 minutes, if you happen to have a Concorde handy {Cite} … </snark>

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.

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.

If you want alternative locations, the complete path.

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.

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?)

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 …

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 …

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.

L1 is unstable, so for that reason alone, this option is not practical.
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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.

At the other end of the scale, the 1912 eclipse featured a totality of two seconds. Solar eclipse of April 17, 1912 - Wikipedia

If we’re allowing any viewing location, then you can get a two-week eclipse.

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.

That’s a viewing location on the Moon, with “eclipse” having its usual meaning of “the Sun being blocked by the Moon”.