Mitchell, John

John Michell ( eng. John Michell ; December 25, 1724 - April 29, 1793 ) - a priest from the village of Thornhill ( Yorkshire ), a prominent English naturalist and geologist.

He was engaged in astronomy , optics and gravity , being both a theoretician and an experimenter. He discovered, in particular, the wave-like nature of earthquakes , carried out a number of original studies in the field of magnetism and gravity, foresaw the possibility of black holes , and proposed a method for the production of artificial magnets. He was called the father of seismology.

In a letter dated November 27, 1783 , which he sent to the Royal Society , Newtonian celestial mechanics and corpuscular optics were combined. The letter contained the concept of a massive body, the gravitational attraction of which is so great that the speed necessary to overcome this attraction ( second cosmic speed ) is equal to or greater than the speed of light with a calculation from which it follows that for a body with a radius of 500 solar radii and with a density The sun's second cosmic velocity on its surface will be equal to the speed of light. ^[2] Thus, the light will not be able to leave this body, and it will be invisible ^[3] . Mitchell suggested that many such inaccessible objects could exist in space.

For the first time, he proposed using torsion scales to determine the gravitational constant and built a prototype of an instrument for measuring the mass of the Earth, but he did not manage to carry out an experiment and carry out the calculations on his own.

I tried to measure the pressure of light by focusing the light rays on one end of the compass needle, but during the experiment the needle melted.

After Michell's death, his equipment was transferred to a member of the Royal Society of London, Henry Cavendish , who calculated the mass of our planet (see: Cavendish Experiment ).