2025-12-04
45 分钟I want to start this week's podcast with a demonstration.
I've got a tennis ball with me and I'm about to throw it against the wall in this studio.
Now, every time I throw the ball against that wall, I know that it will bounce back.
I know that
because Isaac Newton wrote down the physical laws that describe what happens when objects move,
fly or hit each other.
His equations of motion describe things like force, acceleration and so on.
They're very simple and incredibly useful at predicting everything from the movements of tennis balls to rockets to the orbits of planets around the Sun.
Now imagine I wanted to do my demo again,
but this time with something much smaller than a tennis ball.
Much, much smaller.
Something...
Like an electron.
If I could somehow throw an electron at the wall,
could I use Newton's laws to predict what would happen next?
Well, no.
Because at this scale, Newton's classical mechanics break down.
We've entered the quantum realm.
And in quantum mechanics, particles don't always behave like particles.
They can be waves at the same time.