It seems like a stupid question at first, but I am generally curious about this. Light has energy, and i was informed that all energy holds mass. Now, considering that all energy holds mass, that must mean that light has a weight however infinitesimal. Travelling to the speed of light requires more and more energy as you grow closer and closer to the speed itself. At one point it requires infinite, or nearly infinite amount of energy to travel the speed of light, so potentially; anything with mass would need an infinite amount of energy to travel at or near that speed. It is obviously all speculation, and i am probably missing something very obvious, but it made for a very interesting conversation with my father and I am generally curious. So tell me; can light travel the speed of light?
Light by definition of the speed of light travels at the speed of light when in empty space. Light has zero rest mass. Light doesn't exist at rest or even at any slower speed. Within optically dense media, light does travel effectively slower, but it is actually being continuously absorbed and re-emitted, wasting time in atoms. Arguably, light does have an effective mass of h*f/c^2 per photon. It is completely consistent with the mathematics of special relativity that light can have mass at the speed of light and zero mass at any slower speed. Can 0/0 = h*f/c^2...essentially yes. Zero divided by zero is any finite number. It is up to other specifiers to specify which finite number.
Light ALWAYS travels at the speed of light. That's how it is defined. More seriously, although nothing can travel at the speed of light, light itself is nothing - or rather it is 'no thing'. Technically it has zero rest mass, so the only way it can exist is to travel at the speed of light. The trouble is that you can't mix Newtonian and Einsteinian (ie relativistic) mechanics.
Firstly, light has no mass,so your assumption was wrong. Secondly, light 'always' travels at the speed of light, because the speed of light is defined by how fast light travels, however fast that may be.
No one has ever seen a traveling photon so there is at least no observational evidence indicating that light has to TRAVEL from source to destination. I my view light is a delayed response to something instantaneous. Since in my thinking light already exists everywhere there is no problem of it having to accelerate and grow mass in the process. The quantization or discrete nature of it can just be attributed to geometry of matter.
You information was incorrect about all energy having mass. Radiation, or light waves contain no mass. Some people argue that it has an 'effective mass' given by some of the E=hf (engery=plank's constant times the frequency), but that's still debated. Reguardless, light has no mass, and that's why it can travel @ the speed of light c. You are correct about accelerating a partlice towards the speed of light would require infinite amount of energy. If you're really intrested look @ Lorentz transformations, and you can see the fairly easy why anything with mass can not reach the speed of light.
