General Knowledge!

[jim360]

Well, obviously the figure comes from consideration of first-order Fraunhofer diffraction effects. In the case of relativistic effects the equations are more complicated. I could work it out if you like.

[BFM_Edison]

Nah, just let me know what the relations are in planck lengths. By the way, for the conversions it would be easier to just use the fact that we want a ratio of 1 km / 30 cm = 10000/3 and just use larger values methinks. So you can distinguish two stars 300 AUs apart that are 1000000 AUs away.

[jim360]

In fact the formula I quoted is slightly inaccurate, though is a good approximation assuming the objects to be black against a white background. Since in fact Fraunhofer diffraction effects depend on the wavelength of the emitted light in fact the angular resolution also depends on this and not merely distance, by the formula

theta = 1.22(lamda)/D

for theta the angle, lamda the wavelength, and D the diameter of the eye. Then 1.22 is the approximate location of the first minimum of the first-kind Bessel function, treating the pupil of the eye as a circular aperture. This leads to an angular value in radians, which must then be multiplied by 180/(pi).

This means that the human eye can resolve blue objects better than it can red objects.

Relativistically the equation can be simply modified by considering the effects of Doppler shift on the wavelength of light approaching the observer.

/off topic

[BFM_JANE]

I have eyes.

[MrMxyzptlk]

Didn't realise that it was such an obscure fact.

Anyway it's about 1 arcminute as Kiwi said. That means that over a distance of 1 kilometre most of us can distinguish objects that are 30 centimetres apart.

He's not actually saying so, but you're up, Kiwi....

[BFM_Kiwi]

Since the NCAA tournament is on, here's a puzzler for you.

A coach in the tournament has a lifetime perfect record of 9-0 in the first round games.

His teams are 26-7 overall in the NCAA tournament.

The question is, how many times have his teams won the tournament?

[jim360]

Once.

[BFM_Kiwi]

Why once?

[jim360]

I think it must be either once and twice. Since I have no idea how the NCAA works I'm assuming it's just a straight knock-out, in which case those 7 losses represent 7 exits from the tournament. Problem is I have no idea how many rounds there are, so I have no idea how to decide between once and twice - so I just flipped a coin. But from the second round onwards the winning record is 17-7.

[BFM_Kiwi]

Yep.  If you lose you're out.  They've been in the tournament 9 times, so with 7 losses, that means twice they must have won.

If you were really clever you might argue that this year's tournament has already passed the first round, so they would still be in the early rounds of this year's tournament, in which case they only won 1 in the past, and are still alive in this one.

Well done.

[jim360]

Woot.

In what year did Tim Berners-Lee invent the world-wide web?

[MrMxyzptlk]

The WWW went live on December 25th, 1990.  (Merry Xmas/WWW!)

He proposed it in 1989 tho.

[BFM_Edison]

Everyone knows Al Gore invented the Internet. Gosh.

[MrMxyzptlk]

Everyone knows Al Gore invented the Internet. Gosh.

1) Al Gore was of single digit age when the Internet was "born," and 2) the WWW is MUCH younger than the Internet.


 


(I was using "inter-networking" in 1974....)

[jim360]

Al gore Mxy is up!!!