Do Photons Have Mass? - Debate & Questions

[harve]

tl;dr
But the idea that something needs mass to be affected by gravity is obviously false - all things that have mass are affected absolutely identically by gravity, they receive exactly the same acceleration, regardless of their mass. So even if they had zero mass, it would be normal to assume they will still be affected in the same manner and get the same acceleration.

Do you mean that light can be accelerated overcoming its constant speed,or simply follows the space curvature? But curvating motion also means acceleration.

 

[Drakkith]

Do you mean that light can be accelerated overcoming its constant speed,or simply follows the space curvature? But curvating motion also means acceleration.

The velocity of light is always c, yet it is affected by gravity and will change its direction of propagation.

 

[pervect]

One thing should be clarified. The velocity of light is always "c" using local clocks and rulers, which means that in a coordinate independent sense, it's always "c".

The rate of change of the distance coordinate with respect to the time coordinate isn't always "c". So it's important to know how you are defining velocity before you talk about it. If you define it as being measured by local clocks and rulers, then it's always constant.

It's a separate argument about why that's the best way to define velocity - I find that it's mostly a waste of time. it may be worth mentioning - errr repeating - that the issue is one of coordinate independence.