# Travel at around the Speed of Light..!

@RA2_007 (151)
India
March 8, 2007 11:07am CST
Does any one think its really possible? What are the possibilities of this to happen. & What do u think will be the consequences?
1 response
@mx_aman (2101)
• India
8 Mar 07
Recalling the very famous second postulate of Special Relativity declared by Einstein (1905): "The velocity c of light in vacuum is the same in all inertial frames of reference in all directions and depend neither on the velocity of the source nor on the velocity of the observer". Einstein's theory of special relativity says that the speed of light in vacuum is always the same (at 299,792.458 km/s) but this is true only for systems that are inertial, which means not accelerating. From Newton's second law: if forces exist implies acceleration exists; this means that special relativity is valid only when no forces are acting; thus it cannot be used when there is a gravitational force present. Albert Einstein himself emphasized this in his paper written in 1917: "The results of the special relativity hold only so long as we are able to disregard the influence of gravitational fields on the phenomena". Therefore for the results of special relativity to hold the systems should not be accelerating (no gravitational forces). In 1915 (10 years after special relativity) Einstein developed another theory called General Relativity that deals with gravitational fields and according to this latest theory the velocity of light appears to vary with the intensity of the gravitational field. For example, an observer outside gravitational fields measures the speed of light locally (in his location) at 299792.458 km/s but when he looks towards a black hole he sees the speed of light there to be as slow as a few meters/sec. At the same time an observer freefalling into that black hole (zero-g) measures the speed of light locally (in his location) at 299792.458 km/s; when he looks towards the black hole he sees the speed of light there much slower; when he looks away from the black hole he sees the speed of light there much faster. If he tries to resist his freefall into that black hole (by firing his rockets for example) he will not measure the speed of light locally anymore at 299792.458 km/s; instead the stronger the g-force that he feels the faster light appears to him. Again when he looks towards the black hole he sees the speed of light there much slower; when he looks away from the black hole he sees the speed of light there much faster. In any case, freefalling or not, he will never see the speed of light outside gravitational fields at 299792.458 km/s. Finally, there is no difference between the effects of g-forces experienced from these rockets and the effects of g-forces experienced when standing on planets, stars... hence an observer standing on a black hole measures the speed of light locally (in his location) much faster than 299792.458 km/s; when he looks towards outside gravitational fields he sees the speed of light there a zillion km/s. So, i thinks it's not possible...
1 person likes this
@RA2_007 (151)
• India
10 Mar 07
Well.. Nice Response mx_aman. thank u very much for ur response.. but because u see light at very high speed how can u surely say u cannot travel at speed of light.. Actually by the term speed of light I mean the old theoritical speed of light...I also said 'about the speed of light'.. not the exact locally measured speed at any instant.. :D i dont know that much physics.. but I'm just fascinated by these ideas..
• United States
10 Jul 09
I have my own theories of a limit that I call the "light barrier", much like the sound barrier. Upon reaching or passing the speed of light, that is, "breaking the light barrier," a phenomenon called optic flash would occur, similar to sonic boom when breaking the sound barrier. As for a physical object holding up at that speed, current materials science has nothing that I expect could withstand it. In other words, your ship would probably explode from the cosmic impacts before you crossed the threshold. So it's not really relevant.