Are photons physical particles? As in could I grab one out of the air and hold it?


Are photons physical particles? As in could I grab one out of the air and hold it?

In: Physics


Photons are… weird. The short answers to your questions are: yes, they’re physical particles; no, you couldn’t grab one out of the air or hold it.

Photons have no *inertial mass*, so they’re not made out of “stuff” in the sense we traditionally think of it. They’re really packets of energy. But energy is basically the same thing as mass for… reasons… so they still react to other matter in ways that mass does. Which is why they can be reflected (mirrors) or refracted (look at a straw in a glass of water).

A photon is physical as much as an electron is physical, and a microbe is biological. Photons are not objects, if that’s what you mean. They don’t have the usual properties associated with matter, i.e. charge or rest mass.

As I understand it, it’s all about fields. How those fields react, in certain situations and conditions, determines how we observe it as either a particle or a wave. That’s my understanding of it.

Both yes and no to both questions. Define physical particle. And your definition would be either incorrect or incomprehensible. Photons are packets of probability wave, like some kind of weird-shaped cloud (definitely not a sphere), they aren’t point objects (actually nothing is, but set that aside for now), but when they interact with something – they do it at an (probably) infinitely small point in space inside that probability wave volume and instantaneously, so there couldn’t be two interaction points for a single photon, even if that photon wave is literally kilometers (that could be and we use that kind of photons, it’s called very low frequency band and it’s used for communication with submarines for instance; an there’s photons with even bigger scales). But that probability wave isn’t actually a photon itself, it’s just that – the probability of a finding photon interacted with something inside that volume. But (again!) photons do (kind of) interact with other photons and even with itself inside that volume, that’s why we can see interference pattern in double slit experiment. That’s really hard to explain, only to accept as a set of rules.

As for “grabbing” a photon – you kind of can do that, but yet again that’s an overstatement. Theoretically, one can make a perfect mirror trap for a photon, inside which it could be moved and even have a mass! That’s because reflection is actually an interaction – photon get’s absorbed and then another photon with same energy is emitted. So, even though photon inside such trap would be same, it’s not specifically that photon you’ve started with, it would be photon emitted by latest reflection, it’s just photon with same energy and wavelength (color). And with each interaction photon pushes that trap slightly (because even though photons doesn’t have mass, they still have momentum). But if trap is at rest, all reflections and that tiny pushes added up to zero over time. But if you accelerate such trap at one side, reflections at opposite side would be a bit more energetic, which feels just like additional mass – i.e. resistance to acceleration.

Actually such mirror photon trap is quite good explanation of why there IS mass. Higg’s mass is just a small fraction of massive objects, like yourself, most of that mass is just that – an incredibly huge amount of interactions of all particles inside your body. And even Higg’s mass isn’t just because of Higgs particles magically making same thing as usual mass, it’s actually just another interactions. The only difference is that without Higg’s field there would be less mass on a paper than in reality, and that would be discrepancy between theory and practice.

So even massive particles, like electrons, would like to be like a photon – massless and travelling at the speed of light, but they just can’t, there’s constantly something in their way (even in totally empty space there’s fields, with which electrons do interact), unlike photons, which can travel through space relatively undisturbed.

Yes, you can grab one. not with fingers, but with literally two mirrors. It takes a half a lab to pull off, and another half a lab to prove that it is really just one photon.