On a warm summer day in early June, as an uncommon sight unfolded at the lush campus of Cambridge University, three squirrels lazily gorged on acorns from their horde upon an oak tree. The distant faint chatter became increasingly intelligible as Albert Einstein, Robert Pound and Jean Baptiste Perrin strolled briskly across the lawns looking for a shade. As they exhausted one reasoning after another under the oak tree, the magnitude of their mental exercise soon placed each in a child-like slumber.
Having had more than their fill for the day, the three squirrels hung the principles of probability by the noose, as they parted a dropping toward the forehead of each of the celebrated physicists. After a few fleeting hours, the three awakened, took a brief look at each other and cracked up uncontrollably. Suddenly though, Perrin stopped laughing. Why?
Having had more than their fill for the day, the three squirrels hung the principles of probability by the noose, as they parted a dropping toward the forehead of each of the celebrated physicists. After a few fleeting hours, the three awakened, took a brief look at each other and cracked up uncontrollably. Suddenly though, Perrin stopped laughing. Why?
16 comments:
No and no :)
Since this isn't open-ended, I'll add a clue every day. Hopefully someone will figure this before the solution is revealed. So here's kicking this off.
Clue 1: Perrin deduced his facial condition to be similar to the others. How?
Say Perrin did not have droppings on his forehead
Since both Einstein and Pound were laughing too
if they were laughing at each other i.e. Einstein laughing at Pound's dropping and Pound on Einstein's dropping basically after a while one of them or infact both of them (given they are intelligent geniuses) must have realised that hey are infact laughing at their own expense
( i.e. they really have dropping on their own forehead) and should have stopped laughing .
But since they do not stop their laughter it dawns on Perrin first (actually this realisation could have dawned on anyone else - see below) that his assumption that they are laughing at each other is probably not true and he too should have dropping on his forehead and thus stops laughing.
In theory any one of Perrin, Einstein, Pound could have figured this and first stopped laughing.
"... they parted a dropping toward the forehead of each of the celebrated physicists."
So Perrin did have a dropping on his head which was visible to the other two.
Dude wat was the previous comment for. i think my comment explains how Perrin deduced by contradiction. lemme know if that does not make sense i can explain..
Abhi has clarified that the first sentence reads as follows "Say Perrin initially assumes he does not have any droppings on his forehead."
The following fact is well founded:
"In theory any one of Perrin, Einstein, Pound could have figured this and first stopped laughing."
The argument that the Einstein and Pound should have figured out something was amiss before Perrin, is dependent on time and it can be argued that Perrin went through his dedeuction process some time earlier.
Clue 2: Add more than mere facts to the perspective of Perrin. Just as the reader steps into Perrin's shoes, Perrin can too.
Rephrasing without the element of time. Read first person i.e. Perrin's view.
Lets assume you don't have a dropping, then the other two won't see your dropping and will stop laughing because they realise they're the ones who have droppings (no body else to laugh at). Since they did not stop, you must also have a dropping, thereby giving two people to laugh at, so you realise you also have a dropping and you stop laughing
You mention that they stopped laughing. So there is a time period involved for the laughter to start and stop, say x units.
"Since they did not stop..." indicates that a deduction was made which included the time to observe their laughter (y units) and time to formulate and prove hypothesis (z units).
Your argument can be therefore be summed up as:
Laughter of the two continued beyond the time it took Perrin to observe and make the deduction which led to self-realization of said dropping. i.e x should not be greater than y+z
This argument therefore is very much dependent on time and is really a rephrase of your earlier solution.
The true solution to this puzzle is not dependent upon the length of laughter or deduction process.
the deduction should be based on the reason that the other two would be laughing at their own expense otherwise (if the dropping was not his head). so the dropping has to be on his head too for them to be laughing. i do not see any other logical solution.
This isn't the solution.
Solution:
Perrin's point of view: Assuming that only Einstein and Pound had droppings on their forehead, Einstein was laughing because he saw Pound with the dropping. Einstein himself would be assuming his forehad to be clean. Since he found reason to laugh with Pound, who did he think Pound was laughing at?
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