Eli5 Why can’t we “know” the speed and position of an electron simultaneously? Why can we only measure one of these properties at a time?

Question

This always confuses me and I’m not sure how it works. Please explain…

In: 252

Answer 1

At quantum scales, the electron is not actually a material “thing” like a small pebble. It’s more like a little wavelet on a surface. The amplitude of the wave at each point indicates how likely it’s actually “there” if measured so it’s a proxy for the position

But the speed of the electron is tied to it’s energy and the energy is tied to the frequency of this wave.

If you want to know exactly where the electron is you would need only one oscillation on one point. But then, you can’t read it’s frequency and don’t know its energy and speed. On the other hand, if the wave was spreading infinitely its frequency would be absolute but we can’t say where it is at all.

So whenever you have this small wavelet you can only kinda know its position because it’s spread around a volume, and the same for its frenquency.

This is exactly the same for a sound : if you want to know it’s frequency you’need a sine wave but you couldn’t tell at all when it happens. If you want to precisely know when it happens, then, there is no frequency to it, it’s just a sudden bump at a specific time.

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EDIT : the observer effect is not the cause, here, the wave nature of the phenomenon is the source.