David J Prokopetz:
That Aspect 3 gives you certain descriptive capabilities is a concrete, objective fact of the setting. That Aspect 3 actions can at least theoretically trump any mortal opposition is also a concrete, objective fact of the setting. Reconciling these two facts is the player's problem, but it's no more a narrative digression than any other case where the player is obliged to explain how they get from point A to point B.
You say "Reconciling these two facts is the player's problem," but doesn't the incompatibility of some sets of facts (being slower than light, beating it in every race) suggest that it's actually a rather large problem?
I think that the outcome of all of this has to be that it is easier to race "a light spirit" than "light." This actually makes sense to me from a physics perspective, since a light spirit represents something a bit more specific and coherent.
I think that it's important to remember that miracles are supposed to be honest. So it's OK with me if you have to actually be racing a light spirit for this to come into play. It's OK with me to say, any time you simply want to beat a laser to the end of a track, "that seems to be outside the scope of Aspect 3."
So we're assuming that what you actually want is to beat a light spirit. It warms up next to you on the track. It's wearing an orange headband and jogging shorts and maybe an E=mc^2 top with a picture of frizzy-headed Light Einstein. The starting gun fires. It uses a level 6 action with 5 Edge or whatever to win the race. And you use Aspect 3.
Naturally you have to stay focused on the Mythic World. If you weren't focused on the Mythic World then your "beat light" concept becomes incoherent.
So it zips off and you run after it. And it seems impossible to beat it to the end, but you have time to race in because time is weird in the Mythic World. You push harder and harder. Pretty soon it's looking back over its shoulder going, "WHAT IS THIS A HUMAN CAN'T CATCH MEEEE." And it speeds up. Because … because it's racing, OK? It's using its "Light Speed: Faster than you Think" Chi technique. And you push even harder. And it's screaming, "THIS IS IMPOSSIBLE." And then, just at the finish line, you pull ahead.
All the physicists who are watching from the mundane world and attempting to track that coherent bit of light that you were racing go, "Oh my God you were right a strong racing intent can entangle with the behavior of a defined light stream. Half of us are going to go commit suicide and the other half are going to become mad scientists now. Our graduate students, meanwhile, will get laughed out of academia. I hope you are happy. We certainly are."
They are being serious. This makes them very happy, but it will ruin their lives.
You say, "But wait — I wasn't trying to beat 'a coherent segment of light,' was I? Shouldn't I have been faster than all light? Shouldn't I have been visible beating a laser beam down the track, or gotten there and had everything be dark, or run so fast as to turn invisible, or something?"
And the answer, of course, is no, because if you wanted to do that, you would have used Aspect 6. You wanted to beat that light spirit in a race. You didn't want to run faster than c. You wanted to run faster than that light guy over there.
Maybe you even wanted to run faster than all of these light guys, in which case you have in fact done something really freaky — made the light image of the place you started running from lag behind you by racing — but seriously, remember that that cannot have been what you were trying to do, even indirectly, even as a player. You may have outrun all of the light but you can't turn around and say, "Well, now that is my new technique," because if you try to do that you will fail. It isn't something you can do. It's a cool special effect that the HG comes up with to describe what you can do.
The weirdness here mostly comes from the Prosaic/Mythic World thing, which says, in fact, that it's not just Aspect — in fact, many of the world's best athletes if they were willing to practically kill themselves (spending 8 Will) for it could do the same. That's the magic of will, for humans, and the magic of flawless perfection, for you.
More generally, remember that Aspect 3 isn't "you win mundane conflicts." Aspect 3 is "you do perfected mortal things. By the way, this automatically trumps any mundane action that it can oppose." You're supposed to be interested in kicking around what this means, but that doesn't mean that the HG has to wait for a totally satisfactory explanation that everyone agrees with before making a ruling. The ruling in a given case, like an incident that goes into a Project circle, is part of how you figure these things out.