Gravitational fields and light beams

As we gaze into the star-studded night sky, we rarely ask ourselves questions about the exact position of the stars. And it will happen that, having accurately determined the distance between the stars, the light rays, heading towards us, will pass near some star or black hole. In this case, the star will change its position in relation to other stars. But, repeating the experiment, we will see the "wandering" star again in its rightful place. The reason for this strange migration of fixed stars is that gravitational fields have the ability to deform spacetime and thus change the direction of the light beam. The amount of distortion depends on the mass generating the gravitational field and how close the light beam travels to it. Moreover, when the light of a star reaches us, having previously passed next to a massive celestial body, we instinctively position the light source as if the beam was coming towards us in a straight line. Because of this, we incorrectly determine the location of the star.

The reason for this strange migration of fixed stars is that gravitational fields have the ability to deform spacetime and thus change the direction of the light beam

No matter how strange the curvature of light rays in a gravitational field may seem to us, science has known this phenomenon for a long time. The idea that a light beam is a stream of particles has been described since the days of Newton. In 1900, Planck's quantum hypothesis confirmed the presence of a particle of light - a photon. Each photon has a certain mass, and if so, then the light rays, like other objects in the Universe, will be affected by gravitational fields.

Thus, as the particle of light moves, it is possible to take into account the effect of nearby stars and planets on it and calculate its space-time coordinates with great accuracy. It seemed so until the second decade of the 20th century. And then Albert Einstein questioned the simplicity of this picture. According to Einstein, gravitational fields affect not the particles of light rays, but the space-time coordinates themselves.

In 1916, Einstein himself calculated that the degree of curvature of light according to general relativity would be three times greater than Newtonian mechanics predicted - on the order of 1,7 arc seconds. And finally, in 1919, a tremendous opportunity arose to experimentally confirm Einstein's theory.

In that year 1919, there was a solar eclipse. During a solar eclipse, the Moon temporarily eclipses the Sun, and you can observe the light rays coming from the stars for some time. Otherwise, the light rays from the star pass next to the Sun and become completely invisible due to the enormous brightness of the Sun itself. And so in 1918, two separate British scientific expeditions went to the tropics in Brazil and the island of Principe. The plan was to make observations of the stars during the eclipse, and then repeat the experiment in the night sky. At the end of 1919, Albert Einstein's predictions were fully confirmed.

Returning to the expeditions, it must be said: today we believe that the data obtained by these expeditions in 1919 were accurate and convincing. But, as the historians of science John Ierman and Clarke Glymour have shown, the evidence then cited for Einstein's correctness was completely inadequate.

The fact is that in 1962 a much better equipped group of British scientists tried to reproduce the results obtained at that time. After an unsuccessful attempt, they stated that it was difficult to interpret the results of the 1919 expeditions.

In addition, back in 1918, an American expedition went to Washington state to observe a solar eclipse. She reported that a 1,7 arc second deflection of light "does not exist". Between 1922 and 1952, 10 more eclipses were observed, and for only one of them data were obtained that gave a deflection of light rays of 2,224 arc seconds, which is significantly more than Einstein predicted. In fact, almost every observation of an eclipse yielded either unreliable or inconsistent data with Einstein's calculations. In the light of these results, many scientists quite reasonably refrained from final statements and supported the general theory of relativity only after its confirmation of a completely different kind appeared.