I'm not a physicist, I'm only taking my first subject on physics in Eng. here in Buenos aires, so I don't know much about it. But i find it so interesting that I spend some deep hours of thought ofently in it, and i just want to clarify this concern: According to relativity your local time respect with someone else's time will dilate in function of the gravity field and your speed respect to him (Is that right?). As you move faster time will flow slower (just a way of putting it because time doesnt flow, does it?). When you get close to the speed of light time will dilate asymptotically to infinite. So if you would move at te speed of light -wich is impossible because it would take an infinite amount of energy- your time relatively to the to the other observer will dilate infinetely. Photons travel at light speed. Therefore time doesn't flow for them. Does that mean that photons are timeless? Their existence is intrinsic to the time sacle of the Universe? Does a photon exist in itself without reggarding the events of the Universe? (I think i know they don't because if you can experiment with photons you are interacting with them of course, but i say it so you would point out what is the logic gap in this thought, if there is). What is it's nature of existence? What can you tell -anything- about a photon reggarding this aspect? Or - of course- What is wrong with my logic? Thank you! PS: Photons are massless aren't they? But they are quantums of energy wich is equivalent to some mass, so it still makes sense thinking about photons as something that can be subjected to the time dilation, doesn't it? Anymodal- Federico.