h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Having thought about what you've said, I see that the first paragraph doesn't really describe dragon curves at all or where they come from. I'll have to rewrite it too.

I agree. Sometimes it's easier to delete the thing then rewrite it when the rest of the entry works.

Well, I say 'easier' - it takes a lot of time either way.

Hi Icy.

Did you find my explanation of the mirror left/right thing explanatory? I think it would be worth putting into an entry, but I don't want to do it unless my explanation makes sense. I know that this is an issue that really confuses a lot of people.

I think there's more than one way of explaining this. I didn't find yours particularly easy, but it's probably accurate enough, and that's the reason we need to write the entry. I have something else at home on this that I can look up.

Thanks, Icy.

The source I have is an audio discussion (on a radio show I recorded). They say it was one of Lewis Carroll's favourite puzzles.

To summarise their solution (and to add some of my observations):

When you stand in front of a mirror you see someone through the mirror standing a few feet in front of you. Now, they're not reflected left-to-right, as when you move the hand on your left, the hand on the left of them moves. Similarly, it's not reflected up-down, as your head is at the top and feet at the bottom, as theirs are.

You are actually reflected front-back. Looking forwards, the things which are in the front, like your nose, are at the back on the guy through the mirror.

The problem is that our brain assumes that the person through the mirror got there by walking around the mirror, as if it were just a pane of glass and then turning around to look at us. So we get confused by some inconsistencies in that image. Any writing on your t-shirt comes out backwards, for example.

Mathematically, it's a reflected transformation, not a rotated one, so it's virtual.

Now, it would be possible to use a mirror to reflect left-right: just put it to the left of you and look sideways at it. Your left arm is now on the virtual guy's right.

And it's possible to get the mirror to reflect up-down - just put it on the floor and stand on it, looking down. The virtual guy is upside down.

We didn't do these, though. We placed it in front of us, so we have reflected back-front.

Yes, that's what I said but better explained.

Hello. Good to see you around.

Hi Gnomon. Yes, I thought I'd pop in and make some work for the moderators.