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Fun math in action here: these two broods emerge every 13 and 17 years, respectively. Those two numbers are coprime, so their least common multiple, the next t
by jjtheblunt 3y ago
Fun math in action here: these two broods emerge every 13 and 17 years, respectively. Those two numbers are coprime, so their least common multiple, the next time a multiple of one will coincide with a multiple of the other, is 13 * 17 = 221, which subtracted from 2024 is 1803, when Thomas Jefferson was president and the previous time the broods emerged in the same year.
- soared 3y agoThats from the article The simultaneous appearance of the two cicada broods – known as Brood XIX and Brood XII – is a rare event, not having occurred since 1803, a year when Thomas Jefferson was US president
- jjtheblunt 3y agoRight but the article didn’t explain the calculation
- lisper 3y agoAlso to the point: the reason that the breeding cycles of these species are prime numbers of years is that it makes it less likely for a successful predator to evolve. To be a successful specialized predator of these species, your feeding cycle has to be a multiple of their breeding cycle which in practical terms means, since the cycles are so long, it has to be a exact match.
- jjtheblunt 3y agoThe 13s also get 17-1 breeding iterations without shared food competition from the 17s, etc, during the breeding days. The coprime periods effect strong attraction to the involved prime periods.
- lisper 3y agoTrue but that’s less of a factor because the two species don’t have a lot of geographic overlap.
- jjtheblunt 3y agoHere's a map to support your observation. https://stateimpact.npr.org/pennsylvania/2019/05/20/everything-you-need-to-know-about-the-cicadas-that-will-soon-swarm-southwest-pa/ https://stateimpact.npr.org/pennsylvania/2019/05/20/everythi...
- cyanydeez 3y agoCrypto mating will eventually be a human endeavour
- test6554 3y agoI want my broods named like my superbowls and final fantasy games.
- swores 3y agoLegend has it that these strange-looking numbers date to even older than the NFL and Squre Enix! :O https://en.m.wikipedia.org/wiki/Roman_numerals https://en.m.wikipedia.org/wiki/Roman_numerals
- TulliusCicero 3y agoI'm really curious how the broods 'know' when to pop out.
- NewJazz 3y agoTiny clocks.
- anon84873628 3y agohttps://www.scientificamerican.com/article/how-do-periodical-cicadas-know-when-to-emerge/ https://www.scientificamerican.com/article/how-do-periodical... Some how they keep track of the growing cycle of the trees they feed on.
- crucialfelix 3y agoWhen I schedule periodic tasks I always use prime numbers for the loop time. That way it's less likely that tasks will be run at the same time. It's not really that important, but I do it as a form of tribute to the cicadas.
- addaon 3y agoOf course, you still need the worst case when they overlap to meet performance requirements, and you just made testing that that much harder.
- Asraelite 3y agoWith enough tasks and/or small enough timing precision, that worst case may only occur once every thousand years or more.
- harrydehal 3y agoHaruki Murakami, is that you?