system
Given the following post, respond as if you're commenting on Reddit:
human
Do photons (and other C travelers) experience an acceleration to C or is the velocity instantaneous?

Or does it not even make sense to define an acceleration to such things? If so, why? For examples sake, say I have an interaction that results in an emitted photon, at what point is it traveling at C? And where does this energy to travel such speeds come from, simply from the system as it goes to ground state which in turn is the energy to fuel the emissions? How can that be enough?
gpt
There is no acceleration, because photons always travel at c.  This is just an intrinsic property of massless particles in general.

> And where does this energy to travel such speeds come from, simply from the system as it goes to ground state which in turn is the energy to fuel the emissions? How can that be enough?

Photons do not have kinetic energy, so it takes no energy to send them flying off at c.  Instead, energy imparted to a photon changes the wavelength of the photon, and the energy of the photon is simply however much energy the system has lost in producing the photon.