# How much longer is this (July 27th 2018) lunar eclipse than others?

According to the BBC the lunar eclipse on July 27th/28th 2018 is the "longest this century".

Longest isn't a very good way of describing things, since it's a relative measure without reference to actual numbers, and implies it's somehow longer in some way that might actually matter in a practical way.

## How much longer is this lunar eclipse than:

• An "average" lunar eclipse?
• The next lunar eclipse?
• The shortest lunar eclipse this century?
• The 2nd longest lunar eclipse this century?

(Feel free to add in any questions/answers I might have missed that may explain "longest" in a better context.)

The NASA has a lot of data on eclipses. I've pulled the table for the 21st century in Excel. There are 228 eclipses of which 85 are total. The durations below are for the totality phase.

The duration of today's eclipse is 103 minutes.
The average duration is 68.7 minutes.
The duration of the next total eclipse, January 21st, 2019 is 62 minutes.
The shortest eclipse this century, April 4th, 2015, is 4.7 minutes.
The second longest eclipse this century, June 26th, 2029, is 101.9 minutes.
The median duration, as requested by @FooBar is 71.7 minutes (slightly more than the average).

For what it's worth, here in the Netherlands it's probably also the warmest lunar eclipse ever; at sunset, when the moon rose, it was 31°C.

• That's very cool. I had no idea lunar eclipse length varied so much! Jul 27, 2018 at 21:45
• The extreme variability in duration is due to the fact that Earth's umbra at the distance of the Moon is about 2.6 times the Moon's diameter. So it depends on where within that circle the Moon crosses. astronomy.ohio-state.edu/~pogge/Ast161/Unit2/eclipses.html Jul 27, 2018 at 23:00
• Perhaps you could also report the median, which I find much more informative here than the average duration (assuming here "average duration" is the arithmetic mean) Jul 28, 2018 at 13:21
• It's 71.7 minutes, not much higher than the average. Jul 28, 2018 at 13:27

The NASA NASA Five Millenium Catalog of Lunar Eclipse says that the longest total lunar eclipse was 106.6 minutes or 1 hr 46.6 minutes. The link for this century shows that the July 27th eclipse is indeed the longest at 1hr 43 minutes (rounding up). So it is definitely up towards the maximum length at ~96% of the longest known. Two times can be given for eclipse duration; the full duration measured from first to fourth contacts i.e. when the shadow of the Earth just touches the edge (limb) of the Moon to when the shadow just leaves the Moon on the other side. The second duration is that of totality from 2nd to 3rd contacts during which time the Earth's shadow completely covers the Moon.

EDIT Corrected eclipse timings discussion