Your favorite riddle/paradox?

[The debater]

I've always enjoyed a good riddle or a paradox which get's me thinking.

any good ones?

Post an original if you please ?

 

[SocalOmega]

If a tree falls in a forest, but no ones around to hear it, does it make a sound?

 

[Snoopchicken]

How about a math riddle? I didn't make this up, but it's very nice, nonetheless.

"A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony:

There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?"

No Google!

 

[Gladiatus]

A young boy does a paper round every morning, he lives on the 20th floor of his flat, when he goes to do his paper round he goes to ground floor, yet when he returns he goes upto floor 10 and then walks up 10 flights of stairs to his flat, why does he do this?

PM me for answer/think you've got it, you might find on google :s

 

[The debater]

^Because he's too short to reach the button?

 

[SexayMistahBee]

A cat is placed in a box along with a bomb that has a 50% chance of exploding. There is no way to know if the bomb exploded and killed the cat without opening the box.

You have not opened the box yet.
Is the cat dead or alive?

 

[thatguy1234]

There once was a bitch, she climbed a tree. She was fine as shit, thick as can be. She walked towards me, thighs shakin as she comin. I thought to myself what a spectacular woman. Then shawty.

How many apples does Todd have left?

 

[Emperor Nero]

A cat is placed in a box along with a bomb that has a 50% chance of exploding. There is no way to know if the bomb exploded and killed the cat without opening the box.

You have not opened the box yet.
Is the cat dead or alive?

That isn't Schrodinger's cat.

Schrödinger's Cat: A cat, a flask of poison and a radioactive source are placed in a sealed box. If an internal monitor detects radioactivity, the flask is shattered, releasing the poison that kills the cat. The Copenhagen interpretation of quantum mechanics implies that after a while, the cat is simultaneously alive and dead. Yet, when we look in the box, we see the cat either alive or dead, not both alive and dead.

or directly from Schrodinger himself:

One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter, there is a tiny bit of radioactive substance, so small that perhaps in the course of the hour, one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges, and through a relay releases a hammer that shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The psi-function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts. It is typical of these cases that an indeterminacy originally restricted to the atomic domain becomes transformed into macroscopic indeterminacy, which can then be resolved by direct observation. That prevents us from so naively accepting as valid a "blurred model" for representing reality. In itself, it would not embody anything unclear or contradictory. There is a difference between a shaky or out-of-focus photograph and a snapshot of clouds and fog banks.

While I am a fan of the cat I really do like the Liar's Paradox.