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masterofshadows t1_j8gp7z2 wrote

Reply to comment by Weed_O_Whirler in Light traveling through a medium that slows it. Does the same photon emerge? by TheGandPTurtle

>elementary particles are all fungible. That means, they are truly identical, and they are impossible to label. So, if a photon is absorbed and then remitted, it doesn't really make sense to say "is it the same photon or a different one?" There aren't really "same" or "different" photons, there's just photons, unlabeled.

So then do we know for sure photons actually move and don't just vibrate or something causing the next one in the chain to vibrate or something like that? Kind of how AC current works except with photons?

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HoldingTheFire t1_j8gzz8b wrote

Because photons aren’t traveling through a medium of photons. It’s a propagating electromagnetic field.

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mckulty t1_j8gsewc wrote

> So then do we know for sure photons actually move and don't just vibrate or something

That's like asking "is it a particle or is it a wave?"

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silent_cat t1_j8hwizj wrote

Think of the ripples on a lake made by throwing a stone. The water is only going up and down, but the waves move forward. Is that the same wave, or is it a new one?

How would you label a wave to distinguish it from a different wave?

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BlazeOrangeDeer t1_j8hnofd wrote

They are vibrations of quantum fields (in this case the electromagnetic field), so you can say that the fields are passing energy, momentum, angular momentum, etc from one place to another, and this "bucket brigade" of physical quantities is what we call a particle.

You could technically describe this as photons continuously being destroyed as they create new photons in adjacent locations. But it's not that physically meaningful, it's like adding +1 and -1 to the same side of an equation. It doesn't really do anything but use more ink.

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binarycow t1_j8gxe0t wrote

>So then do we know for sure photons actually move and don't just vibrate or something causing the next one in the chain to vibrate or something like that? Kind of how AC current works except with photons?

Does it matter if individual photons move?

All that matters is the end result.

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