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# Wiki Contributions

In general Perpetuals trade above the price of the underlying coins

I’m confused by this. Doesn’t this means that long positions almost always pays short positions, even if the index is increasing ? If so, why would anyone go long on the future ?

I don’t understand where that 1/2 comes from. Unless I have made a gross mistake P(A|A => B) < P(A) even if P(A&B) > P(A&not(B)). In your first example, if I swap P(AB) and P(A&not(B)) so that P(AB) = .5 and P(A&not(B))=.3 then P(A|A=>B) = .5/.7 ~ 0.71 < 0.8 = P(A).

You’re right, the 2^(-3/4) (and the 2^1/4) is probably quantitatively wrong (unless each side is perfectly heat-conducing but both are isolated from each other. Or if the planet is a coin facing the sun. You know, spherical cows in a vacuum…). But I don’t think that changes the qualitative conclusion, which hold as long as the bright side is hotter but not twice as hotter than the perfectly-heat-conducing planet.

Given perfect conduction (uniform surface temperature, bright side and dark side have the same temperature at all times), https://en.wikipedia.org/wiki/Black-body_radiation#Temperature_relation_between_a_planet_and_its_star applies : temperature does not depend on rotation speed. Then T = T_sun sqrt(R_sun/(2D)) ; it is the temperature T that balance incoming radiation P_inc = pi (R_planet^2) (R_sun^2) (T_sun^4)/(D^2) and emitted radiation P_em = 4 pi (R_planet^2) * T^4

Let's suppose no conduction at all. The bright side and the dark side does not exchange heat at all. Let's take two limiting cases : tide-locked planet, and an "infinitely fast" fliping planet.

In the first case, the dark side of the planet is at absolute 0. The bright side of the planet receives the same incoming radiation but emit half its radiation (halved surface) -- change 4 pi to 2 pi in P_em. Its temperature is T_bright = 2^(1/4) T. Average temperature of the planet is (0+T_bright)/2=2^(-3/4) T

In the second case, each side gets half the incoming power from the sun and radiates half the energy (surface halved). Average surface temperature of the planet is the same that the average surface temperature of any side, which is the same temperature that the perfectly conducting planet, T (the .5 from halved incoming power and .5 from halved outgoing radiation cancel each other).

So : rotation raises temperature of a non-perfectly-heat-conducing planet, bringing its surface temperature closer to the perfectly-heat-conducting planet surface temperature.

Yes, "intrication" is the standard translation of "entanglement" in QM. But nobody else uses it, and therefore I fear there is an obvious failure mode where someone Googles it and start shouting "WTF is that?"

"évidence" the noun is just a shorthand for "obvious thing" (most typical usage is « C’est l’évidence même » = “It’s obvious”. « Ce n’est pas la peine d’asséner de telles évidences » = “Such obvious things are not worth stating”).

Great suggestion, I’ll look into that.

Yes, that means « obvious »/« self-evident »

I’m trying to translate some material from LessWrong for a friend (interested with various subjects aborded here, but can’t read english…), and I’m struggling to find the best translation for “evidence”. I have many candidates, but every one of them is a little bit off relative to the connotation of "evidence". Since it’s a so central term in all the writings here, I figured out that it could not be bad to spend a little time finding a really good translation, rather than a just-okayish one.