Why do Mirrors Reverse Text?

Why does text show up backwards in a mirror?

Like, my shirt, for example, says NASA.

But in the mirror, it kind of looks like it says A to a backwards N. Why?

You might think that's just a property of mirrors.

They flip things from left to right.

But that's not true.

Take, for example, this object, an arrow clearly facing from left to right.

But it's also facing left to right in the mirror.

I mean, no matter how I orient this object, it's going to have the exact same direction in the real world as it does in the mirror world.

So if mirrors don't flip objects, why does text show up as flipped?

Well, there's actually an explanation for this.

Let me demonstrate.

If I take this book, clearly the title is forwards, but in the mirror, it's backwards.

Contrast that with the text I've written on this transparent Ziploc bag.

Forward text in the real world, but also forward text in the mirror world.

Why is that?

Well, that's because I did something different with the bag than with the book.

With the book, you can clearly already see the cover of the book, but in order to see it in the mirror, I have to flip it, because right now you're looking at the backside.

To see the cover, I physically flip the book and thus flip the text.

Compare that with a Ziploc bag.

Here, you don't have to flip anything because the bag is transparent.

And so if it's forward in the real world, it's also forward in the mirror world.

In fact, if I wanted to, I could also flip it in the real world.

Now the text is backwards in the real world, but also backwards in the mirror world.

So it's actually not the mirror that's flipping anything from left to right.

It's the human.