ELLIOT SPENCER: Now it's time to beat the conundrum with a little bit of lateral thinking. Apart from the fact that you're not here, Ruben, what is the problem? Quick!
RUBEN MEERMAN: Chill out, relax, I'm here. The problem is, young Elliot, the light-bender conundrum. And to demonstrate, I'll need one of these.
ELLIOT SPENCER: What is one of THOSE and how are THOSE made?!
RUBEN MEERMAN: Ha-ha! Well, one of those is called a 'decoder'. And to make it, all you do is you start with a very clear straw. Get them from juice shops. You Fill them up with water. Just dip mine right into some water, keep your finger over the end. It's got water in it now. Seal up one end with a bit of putty. Seal up the other end with putty, trapping all the water inside. And now you've got yourself a little proper decoder.
ELLIOT SPENCER: So, basically, what you're telling me is that when it comes to you, decoder is code for 'sealed, clear straw full of water'?
RUBEN MEERMAN: Mm. In a way, yes, but this decoder can actually decode, for example…
ELLIOT SPENCER: Example? Ooooh!
RUBEN MEERMAN: Can you read this coded message?
ELLIOT SPENCER: Oh. Hmm. Well, I can see it but I can't read it because it's encrypted. Quick, Ruben, show me how to use that decoder. This could be a vital message from the rebels.
RUBEN MEERMAN: Alright, well, to use it, take yours, lay it over the top of that code — yeah, excellent — look through and now lift it off the page and tell me if anything's changing.
ELLIOT SPENCER: Ooh! They're flipping.
RUBEN MEERMAN: Yes.
ELLIOT SPENCER: I can tell everyone that the code is 'Keep this code secret'. What kind of a message is that?! And, more importantly, how did this water in the straw decode that message?
RUBEN MEERMAN: Right. Great question. Well, the water in the straw now has a curved surface because a straw is a cylinder.
ELLIOT SPENCER: Mm-hmm.
RUBEN MEERMAN: Whenever you have a clear substance with a nice curved surface, it will do things to light. For instance, the lenses in your glasses magnify light. The lens here is called a 'cylindrical lens' and it doesn't just magnify it, it flips images completely upside down. So it takes this image, flips it upside down and makes that suddenly read 'Keep this code a secret'.
ELLIOT SPENCER: Very clever. But, even more importantly, what is the conundrum?
RUBEN MEERMAN: Oh, yes, the conundrum. The conundrum is if you use your secret code-decoder to look at these words — there's 'box', 'art', 'hood' and 'sun' on this page — when you look through those with your decoder, why is it that some of the words flip upside down and some do not? Have a look. Check out what happens.
ELLIOT SPENCER: OK, righto. Um… Ooh.
RUBEN MEERMAN: Notice?
ELLIOT SPENCER: Ooh, yes, tricky.
RUBEN MEERMAN: It is tricky. Would you like ten seconds of thinking music, Elliot?
ELLIOT SPENCER: I would.
RUBEN MEERMAN: Well, then, let's crack out the old spoons. (Hums) And… (Hums, plays spoons)
ELLIOT SPENCER: Wow.
RUBEN MEERMAN: Pretty special. Time's up, Elliot. What do you reckon is going on?
ELLIOT SPENCER: Well, I've been watching all this flipping, and I think gymnastics.
RUBEN MEERMAN: No.
ELLIOT SPENCER: Uh, um… the colour of the ink?
RUBEN MEERMAN: No.
ELLIOT SPENCER: Uh, well, why, then?
RUBEN MEERMAN: Mm-hmm. Vertical symmetry.
ELLIOT SPENCER: You mean buried standing up?
RUBEN MEERMAN: No, I didn't say 'cemetery'. I'm talking about symmetry. When you use the decoder to look at the next line of letters, just watch what happens. Just take it off here and there's a whole…
ELLIOT SPENCER: There's page after page. We're looking at those, and if I pull it away slowly, they all flip, they all look weird.
RUBEN MEERMAN: Correct. Now, look at what happens when you look at the next line of letters.
ELLIOT SPENCER: (Hums) Uh, well… they're all the same, they didn't flip.
RUBEN MEERMAN: Right. Very good. Yes, they did, flip, though — you couldn't tell because they have vertical symmetry. What does vertical symmetry mean? Have a look at these letters. The letter A, if you flip it upside down, looks upside down. But the letter B, flip it upside down, looks exactly the same. It's got vertical symmetry.
ELLIOT SPENCER: So, 'box', 'art', 'hood' and 'sun' had nothing to do with the ink. It was because the letters in 'box' and 'hood' look the same when flipped, but 'art' and 'sun' don't have vertical symmetry, so they looked different when flipped.
RUBEN MEERMAN: Correct. The colours were just a red herring.
ELLIOT SPENCER: You know what I've learned?
RUBEN MEERMAN: What have you learned, Elliot?
ELLIOT SPENCER: I've learned not to flip out over flippant letters.
RUBEN MEERMAN: Flippin' A.
ELLIOT SPENCER: Yes. And I might change these for my glasses.