#2971: Celestial Event
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Approximate frequency in my area
Active northern lights: 20 days per solar cycle
A naked-eye "Great Comet": 2 months every 50 years
Total eclipse: once every 350 years
Clear skies: 50% of the time
17-year cicada emergence: 2 months every 17 years
opening bracket
20 days over 11 years multiplied by
2 months over 50 years multiplied by
1 over 350 years multiplied by
one half multiplied by
2 months over 17 years
closing bracket to the power of -1
equals 4.3 billion years
[Caption below the panel:]
Every 4 billion years or so, my neighborhood gets to see a really spectacular show.
(Sourced from explainxkcd.com)
Title text:If we can get a brood of 13-year cicadas going, we might have a chance at making this happen before the oceans evaporate under the expanding sun.