The universe appears "old", but it is still less than 10,000 years old

[Zen Badger]

So numerous experiments proving the calculated speed of light don't count then?

They either are round trip times, in which case they are convention independent, or they depend on the synchronization convention and implicitly use the isotropic convention (which is the one that says that everyone at rest with respect to you has the same time, which you get if you transport a clock infinitely slowly to that person).

p.s. what do you mean by calculated speed of light?

Regardless of whether they are round trip times, it still took time for the light to traverse that distance.

And Ole Romers discovery in 1676 that light had a finite velocity was based on the measurement of light travelling in one direction, not a round trip.

Or am I missing something?