Galilean principle of relativity: the door to a new scientific reality
The history of science of mankind is a steady movement in the ascending line, in which, nevertheless, a whole series of abrupt moments can be distinguished. These key points correspond to the works and discoveries of those scientists who opened new pages in one discipline or another. One of these pages was the principle of Galilean relativity and the associated beginning of the formation of a mechanistic picture of the world.
Galileo and his circle of scientific interests
The name of one of the greatest scientists of the last millennium, Galileo Galilei, is known to most modern people mainly in light of his conflict with the Catholic Church because of the attempt to substantiate the heliocentric system. Meanwhile, he was a comprehensively developed scientist. Experiments of Galileo in astronomy gave humanity the discoveries of Jupiter’s satellites, the planet Neptune and the presence of craters and depressions on the Moon.From the point of view of philosophy, Galileo scientifically substantiated the erroneous views of Aristotle on the Universe as a set of ideal spheres, in the center of which the Earth is located. It is from the research of this scientist that the scientific method originates, in which the main role is played by the collection and processing of information to confirm or refute certain hypotheses. However, the main place in the works of Galileo was given to all the same physics.
Galilean principle of relativity: prehistory
Up to the middle of the XVI century, the dominant system in the construction of the world was the Ptolemy system, the main postulate of which was considered to be the static position of the Earth in the center of the Universe and the dynamic motion of all the other celestial bodies around it. This system was complemented by the natural-philosophical provisions of Aristotle, one of the most important of which is that the speed of a body in free fall is proportional to its mass. Copernicus carefully studied the works of almost all his predecessors, conducted various experiments in order to substantiate a fundamentally different, heliocentric model. With this, the figures of the Catholic Church,who did not want to miss the ideological and scientific primacy, insisted that this system was in conflict with the surrounding reality. For example, they argued that if the Earth really moved, then heavy objects would never fall strictly vertically. All in its place laid the principle of Galilean relativity.
Reference systems for mechanical movement
To understand the principle of Galilean relativity, it is necessary to keep in mind that at that period of time (as, incidentally, more than three hundred years later), scientists sought to reduce all physical changes to understandable to all mechanics. A special role in this was played by the coordinate systems, the primacy in the study of which belonged to the French philosopher R. Descartes. Here the most important point is that the position of a particular body in a certain period of time is determined either by two (on a plane) or by three coordinates. However, in order to create this virtual coordinate system, a fixed reference point is necessary, that is, another system. It was in this plane that Galileo began to consider mechanical motion.
In his studies, Galileo drew attention primarily to the so-called inertial systems. Today, even an ordinary schoolchild can hesitate to say that such systems are those that are relative to each other, either in a state of complete rest or in the process of uniform rectilinear motion. Inertial systems in classical physics play the role of the pillar from which one can move towards the realization of truth in relation to all processes occurring in the surrounding world.
The essence of the principle of relativity Galileo
In his most famous work, in which the systems of Ptolemy and Copernicus are compared from different angles, Galileo pays special attention to the formulation of the concept of relativity. In order for his positions to become clear to the average man, the scientist works through examples. So he invites the reader to visualize the cabin of the ship, which stands motionless. In the room, butterflies and flies fly in different directions, water drips from a drop of water from one vessel to another. At that moment, when the ship begins to move evenly, nothing will change in the cabin: the flies will move at the same speed, and the water will also flow from the upper vessel to the lower one.Hence the famous Galileo principle: all inertial systems are similar to each other, that is, when moving from one such system to another, the equations of classical mechanics do not undergo any changes.
Galileo principle and non-inertial systems
Regarding inertial systems, the principle of relativity was understandable and was not specifically challenged by anyone. But will it also act in non-inertial reference systems, that is, in those where one system is moving relative to another (which, in turn, is inertial) with some acceleration? Galileo, due to his limited knowledge and imperfect research instruments, could not answer this question. Subsequently, Einstein convincingly proved that in non-inertial systems, acceleration has a direct effect on the processes occurring within the system. This was one of the proofs of the limited principle of Galilean relativity.
The disadvantages and limitations of the principle of Galileo
The Italian scientist made his research a real revolution in the scientific world. However, over time, a number of its provisions, including the notorious principle of relativity, showed their limitations and were more or less revised.One of such examples was shown above. You can also point out that in all studies of Galileo, time was taken in extremely small gaps, while these gaps were considered equal for both systems. However, the same Einstein began to consider time as another coordinate for the reference systems, and he proved the possibility of its non-uniformity when it comes to speeds approaching the speed of light. At the same time, if we consider short-lived events, Galileo’s principle of relativity fully confirms itself.
The development of the principle of Galilean relativity
The teaching of Galileo over the past five hundred years has passed a long and thorny path. If at the beginning the main opponents of it were theologians, then later Galileo’s principle of relativity was repeatedly questioned by prominent scientists. Many have assumed that, with advanced instruments, motion can be detected while inside the inertial system. In the end, at the end of the 19th century, the American physicist A. Michelson conducted an experiment using an interferometer invented by him. This device made it possible to detect even the smallest deviation, but even here the result turned out to be negative.Using this experience, Einstein finally formulated the Galilean principle of relativity for all inertial systems: no physical devices and methods can detect movement inside this system. This principle has become one of the cornerstones for his special theory of relativity.