Is it physically possible for an object to achieve the speed of light if it is in a gravitational field strong enough and the mass does not collide before it attains a velocity of $c$? It is true that the mass of the object approaches infinity as its speed approaches $c$, but maybe there could be an (almost) infinitely powerful gravitational field (increasing in strength as the mass speeds up) originating from a very long distance away, which could accelerate the mass to this impossible speed? I ask this because it appears that you would not need an infinite amount of fuel for taking the object to the speed of light.