[tejohnso]

I recall Neil deGrasse Tyson mentioning that the whole earth would be smoother than the smoothest billiards ball if scaled down. I found that surprising.

[gregoriol]

Wow, that scale! Thanks for posting that!

If my calculations are right, Earth's diameter is about 12000km and its highest/lowest places are about 10km, so about 0.001 If a billiard ball is about 10cm, it's highest/lowest places equivalent to earth would be 0.1mm.

Not sure what are the standards for billiard smoothness, but that seems very smooth to me.

[zokier]

0.1mm is not very smooth. According to wikipedia, 150 grit sandpaper has average particle size of 90-100µm

edit: of course there is vigorous internet commentary about billiard ball smoothness compared to earth:

https://possiblywrong.wordpress.com/2011/01/03/is-the-earth-...

https://skeptics.stackexchange.com/questions/10763/is-earth-...

https://billiards.colostate.edu/faq/ball/smooth/

Which mostly seem to agree that earth definitely is not as smooth as a (new) billiards ball, but there is lots of debate about the details.

[aardvark179]

A billiard ball is about 50mm in diameter. I guess the question is to what tolerance they are made. I wouldn’t expect a small feature to stick up (you’d be able to feel or see those fairly easily) but the overall deviation from a perfect sphere could easily be that large.

[B1FF_PSUVM]

Me too, I was going with "smoother than an orange", the billiard or bowling ball seem excessive - https://what-if.xkcd.com/46/ posted here

[HopDavid]

Tyson has pretty low standards for rigor and accuracy. Take everything he says with a grain of salt.