Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 09/02/2014 13:30:01

Title: Why are planets round?
Post by: thedoc on 09/02/2014 13:30:01

Paul Anthony Weston <> asked the Naked Scientists:
   
Why are planets round, and not lumps of rock?

Paul Weston

What do you think?

Title: Re: Why are planets round?
Post by: RD on 09/02/2014 13:46:54

Quote from: thedoc on 09/02/2014 13:30:01

Why are planets round ...

A. by definition (#2) ...

Quote from: wikipedia.org

The definition of planet set in 2006 by the International Astronomical Union (IAU) states that, in the Solar System, a planet is a celestial body which:

1.   is in orbit around the Sun,
2.   has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and
3.   has "cleared the neighbourhood" around its orbit.

https://en.wikipedia.org/wiki/2006_definition_of_planet


B. because they are/were largely fluid , fluid in space forms a sphere (or an oblate spheroid (https://en.wikipedia.org/wiki/Figure_of_the_Earth) if it is spinning) ...

Title: Re: Why are planets round?
Post by: Aashish Karia on 22/02/2014 22:04:45

I think it is because Gravity is the key, there is an equal amount of gravity pulling in mass on all sides which is why the atmosphere is a constant distance from ground even the surface is so unsmooth.