Celestia Forums

Posted: **20.02.2012, 06:06**

How do I calculate the tidal accelerations and rotational slowdowns of habitable planets and their moons, for making planets with plausible rotation periods and moons at accordingly plausible distances?

Posted: **23.02.2012, 17:23**

A Web search suggests that the rotational slowdown of a planet is quite complicated, depending on a lot of things.

StarGen's module enviro.c includes a "simple" formula, but I haven't managed to figure out all of its terms.

Code: Select all

   base_angular_velocity = sqrt(2.0 * J * (planetary_mass_in_grams) /
                         (k2 * pow2(equatorial_radius_in_cm)));

/*   This next calculation determines how much the planet's rotation is    */
/*   slowed by the presence of the star.                         */

   change_in_angular_velocity = CHANGE_IN_EARTH_ANG_VEL *
                         (planet->density / EARTH_DENSITY) *
                         (equatorial_radius_in_cm / EARTH_RADIUS) *
                         (EARTH_MASS_IN_GRAMS / planetary_mass_in_grams) *
                         pow(planet->sun->mass, 2.0) *
                         (1.0 / pow(planet->a, 6.0));
   ang_velocity = base_angular_velocity + (change_in_angular_velocity * 
                                 planet->sun->age);

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Tidal acceleration and rotational slowdown?

Tidal acceleration and rotational slowdown?

Re: Tidal acceleration and rotational slowdown?