Shiro no Konran - Castle of Confusion

...is that a multiple of it means something on its own.

This is a personal pet peeve of mine. "Ten thousand times the speed of light" means nothing unless you specifically tie it to an external frame of reference, and if that frame of reference is fixed within our Universe, you are breaking relativity just as blatantly.

An observer can move about the Universe as quickly as they like - going to Alpha Centauri and back in ~7.5 hours is not the problem.

The speed of light is the same in all frames of reference.

Alice looked round her in great surprise. 'Why, I do believe we've been under this tree the whole time! Everything's just as it was!'

'Of course it is,' said the Queen, 'what would you have it?'

'Well, in OUR country,' said Alice, still panting a little, 'you'd generally get to somewhere else--if you ran very fast for a long time, as we've been doing.'

'A slow sort of country!' said the Queen. 'Now, HERE, you see, it takes all the running YOU can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!'

- Alice and the Red Queen, Through the Looking Glass

In Newtonian mechanics, the invariant speed is infinite, rather than light's prorogation velocity. No matter how fast you fly, something moving at an infinite velocity would still be moving at an infinite velocity with respect to you. The speed of light is similar - no matter how fast you move, the a photon still moves at the speed of light.

Although 299,792,458 meters per second is not 'infinite', there are infinities associated with it. It takes an infinite amount of energy for something with mass to reach this speed, and even more to actually surpass it. Playing with this while being bound by the limits of our own Universe simply does not work.

Now is relative.