h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

For the sake of precision about AUs, here's the exact data:

The Speed of Light ("c") = 299,792.458 Kilometers per second.

1 Astronomical Unit ("AU") = 149,597,870.66 Kilometers.

1 Light Year ("Ly") = 9,460,730,472,580.8 Kilometers, or
63,241.0771 AU.

1 Parsec ("Pc") = 30,856,804,791,684.9 Kilometers, or
206,265.0 AU, or
3.26157 Light Years.

The Speed of Light and the distance of an AU can be pulled from any really good Astronomy Book. The rest can easily be calculated.

The distance between the Sun and the Earth is figured out by basic mechanics of the Earth's orbit. The exact value, however, depends on the gravitational constant 'G'. This was only recently measured to a high(er) degree of accuracy, proving the mass of the Earth to be lighter than previously thought.
So your 10 or so decimal places don't really hold with me, because the calculations aren't necessarily that accuate in the first place.
So there!