How are photons actually created?

Question

(Searched and although this has been asked before I still can’t find an answer that makes much sense to me)

So how does a photon come into existence, and how can it instantly be travelling at C? I turn on a light bulb and photons are instantly created and travelling at C…but created from what, exactly? The light bulb filament is in a vacuum, but every time I turn on the light bulb new photons are simply created out of nothing (with no “fuel” to draw from)?

I guess I’m struggling to understand how heating the filament results in billions (?) of photons in a constant stream travelling at C, when a millisecond earlier there was just an inert metal thread in a vacuum.

In: Physics

Answer 1

>but every time I turn on the light bulb new photons are simply created out of nothing (with no “fuel” to draw from)?  If there’s no “fuel”, how come you get an electricity bill? 

There’s two ways a photon can be emitted: 

1) An accelerating charge. Note that changing direction and going back and forth are ALSO acceleration. It’s a change in velocity (direction and speed) not just speed itself. So any time you have vibrating charges (like heat vibration in a hot filament), a charge going in a circle (like in particle accelerators) or a charge colliding with an obstacle (that’s how an Xray lamp works), you’re going to get emission of photons. 

2) A particle “dropping down” an energy level. Particles can have more energy than they would like, and in many systems the only way for them to get rid of it is to emit a photon. I honestly don’t know HOW it works, I’m not sure if there strictly is an explanation, but we know that they do and the rules governing when emissions can and cannot happen.

As for why they immediately go at C… Because that’s their nature. Photons are massless and massless particles travel at C.

And yes, I know “photons in a medium don’t travel at c”, but that’s a more complex problem that has to do with charges in that medium, and behaviours of waves, and how they interfere with other waves… and some physicists decided to just stopped calling an electromagnetic wave in a medium a “photon” and call it a “polaron” instead, because it has different properties and therefore isn’t the same particle. But that’s honestly well beyond and ELI5.