You're at a party. Somebody hands you a glass. Hey, come on over here! Somebody else shouts. You take a step and the next thing you know you are wearing that tasty beverage.

But why? When we walk, we keep our torsos straight, don't we? Walking feels entirely steady and constant. So why is it so hard to carry a liquid?

Try This At Home!

If you doubt the difficulty of this exercise, we suggest you try filling up a bucket with water and carrying it at chest level without spilling any. But try it outside first!

The answer is that although we feel ourselves to be quite steady when we walk, in truth that is anything but the case.

When you walk your torso bobs in all directions.

Learn more on this A Moment of Science...

You're at a party. Somebody hands you a glass. Hey, come on over here! Somebody else shouts. You take a step and the next thing you know you are wearing that tasty beverage.

But why? When we walk, we keep our torsos straight, don't we? Walking feels entirely steady and constant. So why is it so hard to carry a liquid?

Try This At Home!

If you doubt the difficulty of this exercise, we suggest you try filling up a bucket with water and carrying it at chest level without spilling any. But try it outside first!

The answer is that although we feel ourselves to be quite steady when we walk, in truth that is anything but the case.

When you walk your torso bobs in all directions.

Learn more on this A Moment of Science...