Sean Carroll

But when you're not measuring it, it's not that there are particles with different positions or different speeds.

So when you ask the question, literally phrased, do the different positions move through space at identical speeds?

No, because there are not quote unquote different positions for the particle, right?

If you visualize it in your head, I have something that looks like, you know, a bell curve, okay?

A distribution with a peak that tails off to right and left, and that's my wave function.

And what I said earlier is that the wave function spreads out over time.

But that spreading out, certainly you could casually attach words to it like different parts moving at different velocities.

But it's not that I can point to a specific position x and saying, what is the velocity of this position?

There is no direct assignment of velocities to positions in that wave function.

There's only the wave function as a whole.

So in order not to get confused further down the road in thinking about quantum mechanics, I think it's worth trying to just be persnickety and get it exactly right, which is the way that you'll get some real insight on what the wave function is actually doing.

Marie Roscu says in episode 268 with Matt Strassler, you were talking about terms in physics that are not accurate, like we say particle, but we mean wave, etc., as we just saw.

And Matt said at one point that he found the word matter interesting.

being problematic and unclear.

And then later I heard Jacob Brandes, another Mindscape guest, in one of his talks saying pretty much the same, and he put it like this.

Anything that is not the gravitational field, that can source gravitational fields or respond to gravitational fields, we can refer to as matter.

Where do you stand on that matter?

Yeah, you know, this is something where I'm pretty forgiving, actually, like in this sort of use of nomenclature.

And maybe I shouldn't be.

I don't necessarily defend my easygoing nature on this particular issue.