The force of attraction

 

Sir, – Isaac Newton must be turning! In your beautiful poster (November 12th) you state, when referring to the force of attraction between masses: “whichever body has the greatest mass will exert a greater force on the other”. This is untrue.

Newton’s law gives the force between the masses: F = Gm1m2/d2. This is the force they exert on each other. It is the effect of this force which is different.

To illustrate: when Felix Baumgartner did his space jump recently, the forces on him and on the earth were equal. Having much smaller mass (inertia) than the earth, he experienced the greater acceleration. Had they equal masses, they would have met half way. Einstein can’t be too happy either, but that’s another story! – Yours, etc,

DERMOT RYDER,

Foxrock Avenue, Dublin 18.