jtotheizzoe:

That’s the official distance from the Earth to the Sun, as recently announced by the International Astronomical Union. Why pick a specific value when the Earth revolves in an elliptical path and the Sun is losing mass over time?

Because scientific calculations from relativity to orbital predictions rely on having an accepted constant. The last time the number was revised was 1976, and we were due for an update.

Use this to wow your physics teachers at your first opportunity.