Is Light Truly Weightless in the Realm of Physics?

[ironbling]

I find it hard to believe that light would be wieghtless. If it was it wouldn't interact with surrounding as it would have no dimensions. Therefore it would travel at infinite velocity, wouldn't diffract, reflect or refract. Also it wouldn't be affected by gravity as gravity needs a mass to act upon as that is how wieght is defined. Therefore if light is weightless it must also have no mass. Thus it follows that it wouldn't be affected by gravity at all for example the kind of gravity that tends to be found around black holes. Am I right or am i missing the point?

 

[dextercioby]

You are...missing the whole point.Light is not weightless.It has mass,relativistic mass
m_{rel,photon}=\frac{h\nu}{c^{2}}
It carries energy and momentum.Therefore both in relativistic and quantum relativistic interactions it behaves just like any other particle,electron,proton,neutrino...
It doesn't have rest mass,that's true,but for physics this is not an inconvenient.Moreover,it's useful,because the lack of rest mass means going at "c" and allowed developing of the Relativity theories and QFT description of other fundamental particles.
Light doesn't have dimensions.As a wave,we can speak about wavelength,true,but as a particle,it's a point particle,it doesn't have legth,width and height.

Daniel.

 

[R0man]

Your reasoning is correct, but the concept of light being weightless goes beyond just its interaction with gravity. In physics, weight is defined as the force exerted on an object due to gravity. Since light has no mass, it cannot experience this force and therefore cannot have weight. This is why we say that light is weightless.

However, this does not mean that light has no properties or interactions at all. As you mentioned, light can diffract, reflect, and refract. These are all properties of light that are related to its wave-like nature. Light is a type of electromagnetic radiation, and it interacts with matter through electric and magnetic fields. This is how light can be bent or reflected, even though it has no mass.

It's also important to note that while light may not have weight, it does have energy and momentum. This is why light can exert pressure on objects, such as in solar sails, and why it can be used to transfer information and transmit signals.

So while it may seem counterintuitive to think of light as weightless, it is a fundamental concept in physics. It is important to understand that weight is a property that only applies to objects with mass, and light falls outside of this category.