printf("%10s  %10s  %10s  %10s\n", "planet", "gravity", "g/earth g", "weight 200");
    grav_mercury = (6.67408e-17*3.3022e+23) / (2439.7*2439.7);
    printf("%10s  %10.2e  %10.3f  %10.3f\n", "mercury", grav_mercury, grav_mercury/ 9.800425,(grav_mercury / 9.800425)*200.0);
    grav_venus = (newton_grav*4.8685e+24) / (6051.8*6051.8);
    printf("%10s  %10.2e  %10.3f  %10.3f\n", "venus", grav_venus, grav_venus/ 9.800425, (grav_venus / 9.800425)*200.0);
    grav_earth = (newton_grav*5.9736e+24) / (6378.1*6378.1);