Why Do Mirrors Reverse Left and Right, Not Up and Down?

课文

1. When you raise your right hand, the mirror image raises what looks like its left hand.

   当你举起右手时，镜中的影像看起来举起了它的左手。

2. This happens because mirrors don’t actually flip left and right — they flip front to back.

   这是因为镜子实际上并不左右翻转，而是前后翻转。

3. Light travels straight from your nose to the mirror and bounces back toward you.

   光线从你的鼻尖直线射向镜子，再反射回你的眼睛。

4. So the reflection reverses depth, not horizontal or vertical orientation.

   因此，镜像反转的是深度，而非水平或垂直方向。

5. If you lie on your side, the mirror will seem to swap up and down instead.

   如果你侧躺，镜子看起来就会交换上下方向。

6. Your brain interprets the reversed depth as a left-right swap because you rotate to face others.

   你的大脑将这种深度反转解读为左右互换，因为你习惯转身面对他人。

7. Try pointing directly at the mirror: your finger and its image point at each other, not sideways.

   试着直接用手指指向镜子：你的手指和镜中影像彼此相对，而非朝向两侧。

8. No mirror can reverse top and bottom unless you change your own position relative to it.

   除非你改变自己相对于镜子的位置，否则任何镜子都无法颠倒上下。

9. Understanding this helps clarify how optical symmetry works in everyday life.

   理解这一点有助于厘清光学对称性在日常生活中的运作原理。

10. It also shows why written text appears backward — the reversal is about direction, not labels.

    这也解释了为何文字在镜中显示为反向——反转的是方向，而非文字本身的标签。