i always wondered about orbits of planets and moons. even with a perfect vacuum with no dust, wouldn't the velocity have to be perfectly adjusted too if there never should be a collision?
The centrifugal force Fc = m * V^2 / r
must match
The gravitational force Fg = g m * M / r^2
From the equation you get V
The exact calculus is much more complicated because the center of mass of the system is not the center of mass of the sun
The orbit is not a perfect circle
You should consider also a tangent inertial force
However the final result wiil be very close to the one you get from the simplified equation, the mass of the sun being much bigger than the one of the earth
