Marx extrapolated the relations of production of the factories of his time into his predictions about the development of the working class. These predictions are among the most important theses of Marxism-Leninism relative to the socialist world-revolution which the working class was to carry out.The physics of Marx' era was not very developed. Marx could have no inkling of the future development of physics and of its application to technology. This is why his predictions had to be in simple and direct proportion to the development of the relations of production of the time.Industry developed — thanks in part to the development of physics — in ways other than Marx had suspected. The use of modern physics, leading to cybernetics and automation, gradually changed the workers from forces of production to supervisory engineers.Were one to undertake today an extrapolation like that which Marx carried out, one would have to see as highly probable the disappearance of the very working class that Marx saw as carrying out the world-revolution.