<Material substance
Leaves a lot of open territory.
I will just say what my father said regarding aliens. "Why does it have to be from outer space? There's a lot of room for other things to exist between atoms, right here." Or to that effect.
There are some similar takes. Ever see KPax? "A bubble looks the way it does because it is the most efficient structure. On KPax I look like a Kpaxian, on Earth I look like a human."
There is an error in the assumption that nothing travels faster than the speed of light. Bell Inequalities create an enormous causality problem with classical physics and its interpretation. A photon knows everything that will ever happen to it - before it happens. We can kind of get around this by arguing that the wave function responds instantly and argue the photon only exists when it needs to, but this doesn't change the fact that events which should be casually isolated end up entangled within a wave function, which results in fun things like the quantum bomb detector, where you can learn information about a thing which didn't happen.
"You don't know how powerful a beam of light is." While, no doubt, this was speculative cryptic statements from the writers to try to get people thinking - a simple beam of light completely wrecks the foundations of physics we have built and challenges every model of material reality. It's an example of productive application of gnostic cryptobabble, rather than simple indulgence in the hedonistic desire to sound superior, which I am obviously quite experienced with succumbing to, myself.