What useless things did you understand recently?

As a matter of fact, the nitrogen makes sky blue, but the oxygen makes it green. Had been more oxygen than nitrogen in our atmosphere, they sky would have been green, all else equal.

You can also say, that this blue color is the color of 20000 K, on the Wein's diagram. Which is the temperature (kinetic energy) of the nitrogen atom hit by an UV photon of the appropriate energy to be absorbed.

And our planet in fact loses water by the hydrogen escaping. 50 kilogram per second.

Well, this I think I know without Googling, You may refine this by - Googling it.

There are lots of cacti that are mostly hairy/fuzzy instead of pointy.

In terms of air flow protection purchased vs biological effort expended, I'm not sure a leaf is better than a spike.

Sorry, I thought it was clinical enough of an illustration not to need a warning. It was in the middle of a BBC News article, after all.

hardly.

Damn. Never thought I'd want to read D in English :) he's quite formidable in the original.

(It's a pity that I can't find anything by Yuri Tynyanov in English; The death of ambassador plenipotentiary (Смерть Вазир-Мухтара) with its odd and wonderful word usage, styled somewhat to Pushkin's times it describes, would be a gem... I really thought it existed in translation.)

But they added so much text!

But the poems, yeah. It was sometimes impossible to imagine this was a translation, after all.

There are a few like that but with some duct tape and a vague understanding of Chinese and monastery culture you can get a glimpse of them. Also seeing multiple translations can give you some clues.

http://bearlamp.com.au/zen-koans/

Also lesswrong post about it -
http://lesswrong.com/r/discussion/lw/p7j/lesswrong_sydney_rationality_dojo_on_zen_koans/

Will publish in a few days, after I present at my local dojo . No guarantee it works because my description is possibly rough and in person I can get feedback on your understanding of the description and say, okay try this explanation instead...

Most of the interesting-tasting or psychoactive chemicals that plants make are there to ward off being eaten or infected. Caffeine and mint oil are among the plant insecticides, all sorts of other things are toxins to vertebrates. By virtue of being megafauna we can tolerate amounts of toxic stuff that will kill smaller organisms by mixing them with other foods, and our particular biochemistry happens to be particularly strong against some (and weak against others, just try to eat hemlock). Stuff we can tolerate but still has effects on us (caffeine, capsaicin) can be interestingly psychoactive, stuff that doesn't hurt us can be interesting to taste (mint, cinnamon, garlic), and there's interesting correlations between spice use and parasite load in food (that could be confounded six ways to mars)...

I guess today I'm learning about Heyting algebras too.

I don't think that circle method works. "Not Not A" isn't necessarily the same thing as "A" in a Heyting algebra, though your method suggests that they are the same. You can try to fix this by adding or removing the circle borders through negation operations, but even that yields inconsistent results. For example, if you add the border on each negation, "A or Not A" yields 1 under your method, though it should not in a Heyting algebra. If you remove the border on each negation "A is a subset of Not Not A" is false under your method, though it should yield true.

I think it's easier to think of Heyting algebra in terms of functions and arguments. "A implies B" is a function that takes an argument of type A and produces an argument of type B. 0 is null. "A and B" is the set of arguments a,b where a is of type A and b is of type B. If null is in the argument list, then the whole argument list becomes null. "Not A" is a function that takes an argument of type A and produces 0. "Not Not A" can be thought of in two ways: (1) it takes an argument of type Not A and produces 0, or (2) it takes an argument of type [a function that takes an argument of type A and produces 0] and produces 0.

If "(A and B and C and ...) -> 0" then "A -> (B -> (C -> ... -> 0))". If you've worked with programming languages where lambda functions are common, it's like taking a function of 2 arguments and turning it into a function of 1 argument by fixing one of the arguments.

I don't see it on the Wikipedia page, but I'd guess that "A or B" means "(Not B implies A) and (Not A implies B)".

If you don't already, I highly recommend studying category theory. Most abstract mathematical concepts have simple definitions in category theory. The category theoretic definition of Heyting algebras on Wikipedia consists of 6 lines, and it's enough to understand all of the above except the Or relation.