# A short and simple riddle

One day, while playing Minecraft, a player ran at full speed up to a tree and dug into the ground. There, they found a mysterious note. It said:

I am a thing.
If you do something to me,
and then do the opposite of that thing to me,
You may think you end up with me again, but...
You will end up with the opposite of me.

What is this riddle referring to?

Hint:

Minecraft has trees made out of cubes.

• It refers to the number zero. If you take the negative of 0, it makes 0, then you take its negative, 0 again, which is also the opposite of 0. – fffred May 25 '16 at 13:08
• Hmm... It's certainly possible to think of the number 0 as a thing, but I'd be leaning more towards it being the absence of a thing. I'll clarify if it's generally accepted as too ambiguous. – Kingrames May 25 '16 at 13:12
• At first I wondered "why did someone downvote this"? Then I realized, they were responding to it. – Sneftel Jun 7 '16 at 11:29

$-1$ (or any other negative number)

Explanation:

Squaring it turns it into 1 and the square root of 1 is 1.
So you end up with the opposite of $-1$.

• @fffred not all things are tangible things. – Paul L May 25 '16 at 13:52
• @ruudvan The square root of 1 is really 1. Do not mistake that with the solution of $x^2=1$ which has two solutions. – fffred May 25 '16 at 14:54
• @ruudvan. Actually the square root of 1 is 1. It's never -1. Never. +/-1 are solutions to the equation $x^2=1$. But it's not the same thing. – Marius May 25 '16 at 14:55
• @fffred it is. Your answer is 100% correct. It's just not the answer the questioner was hoping for. That doesn't make it less correct. – Paul L May 25 '16 at 15:05
• (likewise, @marius's answer is also correct. I suspect that Kingrames made the same error that ruudvan made, in believing that the square root of 1 is +/- 1. There is no "simple and very common mistake" in marius's math, his answer fits the riddle completely.) – Paul L May 25 '16 at 15:10

Another possible answer is: If you

rotate a cube around one horizontal axis, then around the other horizontal axis, then perform the same two rotations in the opposite order, the cube ends up upside-down.

This doesn't work very well as the "opposite" actions aren't proper opposites.

• That's pretty cool, though. Thanks for sharing that. – Kingrames May 25 '16 at 18:56