these should be some very easily answered questions. how does anyone know photons exist? im guessing they can be "stopped" and studdied? and also, after reading about this relativity stuff for the last few days i feel like im getting an understanding, but please, entertain this scenario and try to give me a simple answer: ok, so ive heard the idea that if some left earth and travelled the universe at near light speed they would come back to an earth billions of years in the future. so just to clarify, if i was sitting far enough away from someone that i could watch them move at 90% c with a telescope. would they appear squished length-wise, and would they be moving in slow motion(blinking, heart-beat, muscle movement, ect.. not speed)? thanks, i really need this curiosity satisfyed or it will keep bugging me and finding its way into every damn train of thought i have!