OK. Ya got yer astronauts orbiting earth, or yer satellites, and we know that time passes more slowly for said astronaut or satellite. It's been measured. Still amazes me.

Anyway, let's say you've got an interstellar mission. As the craft flies away from earth at greater and greater speed, the astronauts experience a slowing of time, correct?

But what differentiates the frames of reference? From the astronaut's perspective, the spacecraft is stationary and it's the earth that pulling away at increasing speed. Why then doesn't the earthbound observer experience a slowing of time?

You'd never know it, but I studied relativity in college. Either those particular brain cells have died or simply packed up and left for a more promising gig.