I expect it’s more likely a combination of:
[ul]
[li]Illumination is progressively attenuated from the red end of the spectrum as you descend through water (per JBDivmstr in post #2)[/li][li]The Purkinje Effect (our colour perception shifts toward the blue end of the spectrum as illumination decreases, even if decreasing proportionally across the whole spectrum)[/li][li]Our colour perception attempts to maintain a ‘white balance’ regardless of the properties of the ambient light.[/li][/ul]
Taumatawhakatangihangakouauauotamateapokaiwhenuakitanatahu.
I know π to 10 digits, which isn’t especially impressive I guess.
I try to remember the 50 US States, but I get a bit lost after around 30 and peter out. After some time I eventually get them all, though (I tend to forget Delaware until the very end).
I also know the complete lyrics to the theme to The Gummi Bears TV series.
Once I could type 370 machine-language programs in hexadecimal at a mainframe’s maintenance console (e.g. for a “scope loop”) without consulting a “yellow card.” I had the oft-used op-codes memorized, not all of them. I’ve memorized some other lists, e.g. the 20 lettered Y-haplogroups and when/where they fit in.
The colored resistor codes known to electronic technicians have the rainbow colors in order; the politically incorrect mnemonic was
(bad boys) Rape Our Young Girls But Violet (gives willingly).
This code omits Indigo. We could modify Violet to make her Immodest or Indulging, but I think it would be more proper to replace the final clause with “But I’m Virtuous.”
Knowing the kings and queens in order is useful if you like history (sounds a little obvious, but bear with me) or antiques or art. This is because then you will know what they mean by a Queen Anne chair, or an Edwardian house, or, as long as you remember that George IV ruled for a long time as regent when his dad, mad King George III, was ill, what regency architecture is.
Flags of the world might be good to memorise for quizzes and the Olympics.
World capitals is another good one, especially since they’re not all obvious. Trick question: what is the capital of South Africa? Think about your own answer before googling.
Chemical elements and which groups they belong to. I don’t remember them all, but the parts I do remember and the naming patterns are enough to be able to take an over-educated guess over where will any of the others belong; for example, since I do know all the metalloids and noble gases, any I don’t remember has to be a metal.
IIRC, the blood did appear brown at first, as I ascended it turned a bright green. I may be ‘off’ on the depth at which blood appears green, it’s been a long time since I did any spearfishing. 
And scars burned into your fingertips? 
I can do that- with a fireplace match. 
Anyway, my contribution: 355 divided by 113 gives Pi to several decimal places; good enough for almost any practical engineering purpose.
I’m duly impressed. I’m British – can do the kings and queens regnant in order from 1066 on, thanks to the useful rhyming ditty which helps with same – most of the spouses, no way. And I couldn’t name more than a handful of US presidents, in approximate order, to save my life.
I’ve seen it suggested that the “indigo” bit is basically nonsense – blue and violet shade straight into each other; the “Indigo” thing was invented to make pronounceable drawing-room-suitable aide-memoires possible – VIBGYOR or ROYGBIV.
I’m a railway nut – would bet on my ability to tell you off the top of my head, the predominant track gauge (distance between the rails) in any country in the world that has public railways.
Haven’t googled – in the old days, the capital’s role was divided between Cape Town and Pretoria. God knows what’s done in these more enlightened times.
I’d also probably go with “six” if someone asked me how many colors I see in a rainbow. But the inclusion of Indigo, whether mistaken or not, is much more venerable than you suggest:
[QUOTE=Sir Isaac Newton]
The Original or primary colours are, Red, Yellow, Green, Blew, and a Violet-purple, together with Orange, Indico, and an indefinite variety of Intermediate gradations.
[/QUOTE]
[QUOTE=GuanoLad;
I know π to 10 digits, which isn’t especially impressive I guess.
[/QUOTE]
I was wondering when someone would mention Pi.
When I was 17, on our way back home to Michigan from Tennessee, I memorized the first 100 decimals of Pi.
I’m 45 today and still have it memorized.
For some reason, it doesn’t seem to break the ice at parties.
Pi to 11 decimal points.
My 15 digit driver’s licence number.
My 13 digit bank card number.
My 9 digit social insurance number.
I know the resistor colour code too, and the rainbow.
Is there anyone who doesn’t know SOHCAHTOA?
I know the first 20 powers of two, which was less useless when I learned them.
Used to be able to recite The Walrus and the Carpenter. I could get through most of it right now.
Could name 50 states given a blank map, but probably not from a memorized list. (I’ve been to 40 or so of them).
Probably could list the Presidents if I had to, from knowledge of history, as mentioned upthread.
One semi-useful skill: I can convert measurements back and forth from metric to US units.
Outside of the US, that would be pretty much useless, and even here it’s not something people do all that often.
(The illicit drug trade uses grams. What to know if your teen uses drugs? Ask how many grams there are in an ounce.)
Indeed, one study found that teenagers in the nation’s inner cities excel in metric based calculations.
(Quoting Sir Isaac Newton): “The Original or primary colours are Red, Yellow, Green, Blew, and a Violet-purple, together with Orange, Indico, and an indefinite variety of intermediate gradations.”
Aar, 'e were a funny feller, that Sir Isaac, surely – and 'e loved words as long as my arm. Seriously, though – point taken.
Is it something North American? (That would let me out.)
Mathematical
Sine = Opposite/Hypotenuse
Cosine = Adjacent/Hypotenuse
Tangent = Opposite/Adjacent
(bolding mine)
I’ve performed LEO administered field sobriety tests quite a few times over the years and I’ve never been asked to say the alphabet ‘backwards’. :dubious:
AFAIK, ‘saying the alphabet backwards’ is not an accepted sobriety test.
Not quite the ‘semi-useless trivia’ that the OP asked for, but the following was information well worth learning, IMHO.
First and foremost, I am not advocating ‘driving while impaired’. But with the lowering of legal ‘accepted limits’ of BAC to .08%, it’s a good idea to know how to comport ones self when confronted with having to demonstrate sobriety.
As for a “skill [that] just might be the edge you need someday”, IMHO these are the things that are most likely to make the difference between driving your car home, or going to jail for DWI. :eek:
You have the ‘right to remain silent’, use it. (even though you haven’t been charged and/or haven’t been arrested yet)
Respectfully and politely answer any questions, as succintly as possible.
Don’t be talkative and don’t ‘volunteer’ anything.
Listen carefully to the instructions given, concerning the skill you are about to perform.
These are two things that a LEO will be paying particular attention to, your demeanor and your ability to listen and to comprehend.
If you have been drinking, when the LEO asks you, “Have you had anything to drink?”, he’s not ‘wondering’ if you’ve been drinking, he already suspects that you have, and is wanting to see what your response will be.
Don’t lie, (They hate that.) tell the truth.
It’s how much you admit to drinking, that will make a difference.
The correct answer is, "I’ve had a beer (or a mixed drink), not “a couple of beers” or “a couple of drinks”.
One 12 oz. beer or one mixed drink per hour is enough to put the average person close to the limit of .08% BAC.
You don’t want to confirm that you’ve had enough to put you over the limit. :smack:
Sorry for the ‘hijack’.
"Not many people can tell you what that [THC] stands for off the top of their head… "
I can.
I memorized the presidents (back in high school), and the Kings of England/UK from 1066.
I memorized pi to 14 places.
That’s funny because it’s true.
I can do this with ounces. I guess that’s a semi-useless skill.