If cherries are yellow and egg yolks blue . . .

Factual Questions
1

About one month ago, Parade’s resident “genius”, Marilyn Vos Savant, posed a simple question to her readers and asked for possible solutions. Her question was, “If cherries are yellow and egg yolks are blue, what color is a clear sky at noon?”

Without hesitation I went to my computer with, what I thought, was the correct answer. What follows is my reply:

  • MY GUESS IS BLACK

The normal visible spectrum is from 400nm to 700nm. The range of colors in the visible spectrum from 400nm to 700nm is Violet, Indigo, Blue, Green, Yellow, Orange and Red. A person’s visual color range does not extend beyod the 400nm to 700nm range, so light with wavelengths beyond the visual spectrum will not be seen.

In this theoretical case, cherries which are normally red are being perceived to be yellow. Similarly, egg yolks which are yellow have the perception of being blue. In each case, their normal spectral region has been shifted by 150-200nm (approximately) to the shorter wavelength. Therefore the sky, which a person normally detects as being blue (due to the dispersion of white light by our atmosphere), will be shifted to the sub-400nm region. Since a person cannot detect light in the sub-400nm region, no light will be detected. In the absence of visible light, the “color” that is “detected” is black. *

Sounds reasonable? Well, not to Marilyn. The “correct” answer was printed today, and the color was red. Why? Because “along with yellow and blue, red forms the triangle of primary colors from which all other colors are composed. Cherries, egg yolks and the sky have shifted to a new position on the primary triangle”.

When I went to her web site to determine why black was not a strong argument, it stated:

“Some said that a frequency shift would cause the sky to be the “color” of gamma rays, and one would see only the black of space. This solution is weak because of the unequal treatment of the three puzzle elements.”

(To see why other answers were wrong, visit her web site here.)

What gives? Her answer of red is an equally weak argument (claiming that the three primary colors MUST be represented)!! At least an argument of black uses a scientific approach!!

So who is more correct, Marilyn or I?

2

your logic seems flawless, hers is often flawed.
She is, in spite of the fact that some chump at mensa thinks otherwise, the people magazine of smartypants

3

The Marilyn is Wrong! website catalogs vos Savant’s errors in her columns. However, it doesn’t look like it’s been updated recently.

4

When in Rome, you have Roman judges. Marilyn is correct.
As to your scientific explanation, under what scientific circumstances are cherries yellow and egg yolks blue?

5

It was red that jumped into my head first. It’s not really to do with them being primary colours they could have been non primary coloured things and the puzzle would still have worked, but your idea would not have.

6

Am I the only one who thought this was a trick question? Yes, my first thought was “red”, following the “primary triangle” argument. But nowhere in the original question is it stated that the sky has changed color; it’s merely insinuated.

There’s a trick question posed to schoolchildren: What is the closest star? If the kid answers, “Proxima Centauri”, the questioner can say, “Haha, no, it’s the Sun!” Or vice versa. Either way, you can’t win.

And having mulled over sir vics’s answer, I think it’s at least as valid as Marilyn’s.

7

When you’re moving towards them at extremely high speeds, or when you’re down a strong gravity well from them. On another scientific note, such a frequency shift would only get you to ultraviolet, not to anywhere near gamma rays.

My personal answer to that one was “seven”, for the same reason that a raven is like a writing desk. :wink: When you only give two examples, there’s not really any justification for any answer, over another one. In fact, looking at it logically, any answer is 100% right, since it’s an “if” statement with a false premise. I could equally well say “If cherries are yellow, then I’m the Pope”, and since cherries aren’t yellow, I’m fine.

Niobium Knight, why wouldn’t sir viks’ answer have worked for other colors? It seems to me that his argument would have worked just as well if, say, green carrots were one of the premises.

8

Gamma rays? It would be ultra violet surely???

9

Chronos I never said Sir Viks was right. I was refering to the actual correct answer.

10

I disagree with the frequency shift thing because it’s impossible to tell exactly what the shift it. It could be the sky would be indigo/violet, or it could be ultra violet. The correct answer is obviously red.

It would have worked this way for example (and would not have misled you so much):

If oranges are green, grass is blue, what colour is a clear sky at noon?

11

OK, I guess I’m not looking for a right or wrong answer here. I was just a little p*ssed-off when Marilyn casually discredits my answer because “my argument is weak” and did not take into consideration “all the elements of the puzzle”. My only issue is that my explanation is just as logical and valid as hers.

If you read her column today, she says that she selected the correct response from a reader because it “was the first to come up with my own (Marilyn’s) answer and the reason”.

I understand this is just a hypothetical question, but she should give other theories equal merit if the arguments are logical and sound.

12

Another point to consider with the OP’s answer - you might wish to consider the scattering of currently invisible wavelengths being shifted by your premise into the visible region. Offhand, I don’t know they Rayleigh scattering properties of the atmosphere for infrared frequencies just below visible light. Also, though scattered less efficiently, other frequencies are scattered to some degree. I suspect your “shift” premise would lead to SOME coloration - I don’t know what.

Ms Savant is using the “artist” or “painter’s” primaries in her argument[sup]1[/sup]. There exist other primary sets, including the “additive” RGB primaries we are familiar with for CRT’s, and the “subtractive” cyan, magenta, yellow.

When I read the question I immediately started thinking of RGB primaries, and a non-contrived pattern did not immediately suggest itself (R+G -> B, R -> R+G, B -> ?). I did suspect an answer involving translation of primaries.

I would say there isn’t a single “best” answer.

[sup]1[/sup] - and that you learned about in “primary” school, come to think of it.

13

Yabob, that they are primary colours is irrelent to the puzzle. That they are primary though gives you a clue. Remember those primary colours are the ones that the majority of people are familiar with. You dont need to be Einstein to have a crack at it. It is in fact an incredably easy question, however.

14

I’m with Chronos (and everybody else) on this one; the question is utter wibble.

Besides, there are such things as naturally yellow varieties of cherry; I have no doubt that chickens could be fed something to make their yolks blue and the sky will still be blue.

Bah, I’m joining DENSA.

15

I have another problem with sir viks’ answer that would not interfere with Marilyn’s, though I should note that I don’t think this is a fair question either. Anyway, unless you take the spectrum of a (normal, yellow) egg yolk, you don’t know that the yellow that you’re seeing corresponds to the wavelength of yellow light. For instance, the text in THE STRAIGHT DOPE logo at the top of this page appears yellow to us, but it’s actually a combination of red and green. So, if it underwent the blueshift in question, instead of yellow being shifted to blue, you’d have red plus green being shifted to, I don’t know, green plus ultraviolet? But the point is that the result won’t necessarily be blue.

Now, if someone here has actually taken the spectrum of an egg yolk and found it to be monochromatic, I’ll eat my words. But that is something one would have to take into consideration.

Also, I have to agree with yabob’s first point. If you see an infrared source that is blueshifted the right amount, you would see some definite color, even though we can’t see infrared.

16

If the visible spectrum was 100-200 nm smaller, that is (and let me make this clear), if all WE could see was say 500-700nm, then all the current primary colors that we know now would not be represented, would they?
So The converse applies: if we saw 500+nm of light with our eyes we might have more colors on our palette. We might actually See infrared light. “ooooo, look at that divine infrared vase honey! I just have to have it.”
Visible light has an arbitrary set of parameters for us, a different set for cats, say.
The rule that all three primary colors have to be represented is piffle. It reduces the answer to a parlor trick.
Sir Vics answer on the other hand is simple and needs no a priori knowlege.

17

The philosophical answer: The clear sky will be still blue, since I, and no man ever (except he/she was on LSD) has ever seen yellow cherries or blue egg yolks. The mentioned items do no adhere with our current perception, so any other objects may have any colour you like. I stick with a clear blue sky.

18

I beg to differ:
http://www.nelsmark.com/nels_fresh_cherries.htm
(there are also varieties that are entirely yellow without any pink blushing on the skin, but I can’t find a picture)

19

The yellow variety are called Golden Stark Delicious and look like the ones shown on this page (Please forgive the horrid background music. It doesn’t last very long, though.) Though they don’t give the name, you can also see yellow cherries on this page.

So I guess since there really are yellow cherries, the correct answer to the question, “what color is the sky now”, is blue. Duh. :wink:

20

You people are amazing! :eek: