XKCD: What if Earth grew 1cm every second?

[trappedslider]

Did not know the thing about surface gravity being proportional to radius ,also sweet rings for earth!

 

[Paul Farquhar]

Did not know the thing about surface gravity being proportional to radius ,also sweet rings for earth!

It only works if you assume the Earth is a uniform sphere of constant density - which it ain’t.

It’s denser in the centre, and if you add mass - say by meteorite bombardment, you might expect the core density to increase, and hence the surface gravity would increase more quickly than the radius. However, there is a complication - if you are adding mass you are also adding energy, which would increase the core temperature and tend to have the opposite effect - but the precise calculations are going to depend on what the added mass is made of.

 

[Gradine]

Was pretty sure that was a distinction they cleared up.

Anyway, I'm just here patiently awaiting the video on the Interplanetary Cessna, which was my favorite segment in the book

 

[trappedslider]

It only works if you assume the Earth is a uniform sphere of constant density - which it ain’t.

Did you watch the video because it actually says at the 4 min mark "the density stays the same" then it goes on to explain what would really happen.