F = G x m1 x m2 / r^2.
G = 6.673×10^-11 N
Mass of the Sun = 1.989 x 10^30 kgs
Mass of the Earth = 5.972 x 10^24 kgs
1 light year = 9.4605284 x 10^15 m
Distance to Alpha Centauri AB = 4.37 ly
Distance to Proxima Centauri = 4.24 ly
Mass of Alpha Centauri A = 110% Mass of the Sun
Mass of Alpha Centauri B = 90.7% Mass of the Sun
Mass of Proxima Centauri = 12.5% Mass of the Sun
Mass of exo-planet Alpha Centauri Bb = 113% Mass of the Earth
The force on the Earth due to the Alpha Centauri system is too difficult for me to calculate, so I got out the kitchen scales instead
