I have to disagree with you there...the train doesn't go WITH or come WITH tracks...it goes ON tracks... With indicates that the object is moving too...the train doesn't take the tracks WITH it. the correct answer is NOISE. i thought it was the letter O personally then i googled it and found it to be Noise.
It's a good thing that you ruled out the possibility of communicating in a different manner, like time between people or fast/slow walk. I was just going to say to slap the messenger on the face if it's a red ball...that way it doesn't matter what he says, if his face is red, it's a red ball.
I have a thought. I agree with the above statements about the riddle, but what if you had an LED lightbulb that doesn't generate any heat. can anyone come up with a way to do this with the 3 original switches and only one trip into the next room? I don't have an answer...so don't ask me...let me know if you come up with anything though. thanks
Clarification? It isn't stated, but can you weigh more than one ball per scale at a time? what i mean is...can you put three balls on one side of the scale and three on the other side? or do you have to compare the weight of two balls at the same time, one per each side of the scale? this will make a difference in the number of times that you have to weigh them.