If I understand correctly, an object with mass can't reach the speed of light because at the speed of light it would have infinite mass (and presumably fill the infinite universe). But what happens as an object approaches the speed of light? Eg., if an object traveled at 1% of the speed of light, how much would its mass increase? Certainly it wouldn't fill 1% of the entire universe at that speed. If an object were to reach 99% of the speed of light, would its mass increase proportionately so it theoretically filled 99% of the universe? That seems wrong for a lot of reasons, but what does theory say? Is there an exponential ratio that makes it conceivable for an object to approach the speed of light without noticeably increasing mass? At what point does it become an impossibility? Only at the speed of the light, but at no point before? Which raises the dependent paradox that if the speed of light has a definite value, wouldn't that imply that infinity has a definite value? If an object at the speed of light fills an infinite universe, wouldn't an object at 99.9999% the speed of light fill up 99.9999% of the universe? What would 99.9999% of infinity be? I'm not sure if there's an explanation I'll understand, but it's worth a try.