UFO
abbrivation;undentified flying objects
we are always puzzled,did UFO exist?
maybe, ours galaxy has more and more civilization forms. aliens once came here.
generally speaking,a kind of civilization form existed,it means they had high level technologies,but what could be reflected that?
maths ,perhaps is an unique selection.
what is prime number;
a number can be divided by 1 and itself.
2,3,7,59,1111 e t c.
cicadas,those tubby brown bugs that spend most of their lives underground,emerge from dormancy every 7,13,17 years.
an evolutionary logic behind this pattern.
reproductive cycle[unit;year]
cicadas 1 2 3 5 7 11 13 17 19
its predators 2 3 6 12 18 24 36 42 48
cicadas amount [increase]
while its predator get lower