Man, this is a weird feeling. Man, I grew up knowing 9 planets! Now they go and mess up Pluto's game! Mason will now learn about just 8 (probably -- I remember a lot of out-of-date textbooks growing up).
Funny -- the closest thing I can think of as big as this would probably be on September 11th while I was watching the first tower collapse, I distinctly remember thinking, "Wow, Mason's gonna grow up in a world with just one tower."
Just as earth-shattering? On some level, yes.