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Topic Last Updated on 15-07-2024
Generally, everything is explained at a beginner’s level in school physics, without any complicated mathematical formulas. At the end of their studies, most high school graduates view physics as a complete whole, made up of structures consisting of mismatched blocks: a dozen formulas, scraps of information from different topics, and the firm belief that all the secrets of the universe have been discovered — that’s all there is to it. No need to revisit physics ever again.
That’s not even half the problem! Much worse is the fact that the process of learning itself is much like a leisurely walk along the sidewalk, from one topic to the next. In such an “airtight” education system, the idea that certain views or theories may be erroneous may seem silly!
The Mistake of Ignorance
In reality, many mistakes have been made due to a lack of accurate data. It’s amazing how, on the few available crumbs of knowledge, great thinkers managed to build logically complete theories and create consistent theoretical models that humankind has used for hundreds of years.
For example, take the geocentric system, the theory that the Earth is at the center of the universe. Just at its mention, today’s astronomy students will smirk knowingly. But let’s forget for a moment about the ISS, Hubble, and mobile phones — try to step into the shoes of Anaximander, Aristotle and Ptolemy, and consider the geocentric system from a practical point of view. Does it explain the diurnal movement of the stars? Yes, it does. What about the phases of the planets? Sure. The movement of the Sun along the ecliptic? Again, the answer is yes! That is to say, the vast majority of celestial phenomena are decently explained within the framework of the geocentric model.
Physics | Geocentric model
In this model, the central point in the universe is assigned to planet Earth; all other planets, stars, and the Sun revolve around it. This model does not explain why the planets sometimes move from east to west, that is, in the direction opposite to the movement of the Sun. Moreover, it baffled the ancient astronomers, who regarded the planets as deities that should move only uniformly.
This harmonious system is contradicted by a key fact — the backward movement of the planets. This problem, though, was solved by the introduction of epicycles. They complicate the model a bit, but complexity doesn’t mean that an idea is incorrect.
Geocentric model and epicycles
Epicycles were introduced to explain the uneven movement of the Sun, Moon, and planets in the geocentric model. According to this model, a planet moves uniformly along the epicycle, a small circle (the smaller dotted circle) centered in (•). The center of the epicycle, in turn, moves in a large circle (the larger dotted circle) centered in (×), which is called the deferent.
The pinnacle of this model can be considered a combined geo-heliocentric system, in which the Earth rests in the center, the Sun and Moon orbit the Earth, and all five known planets revolve around the Sun. As one of its creators, the great observational astronomer Tycho Brahe wrote, “This hypothesis would not in any respect contradict either math or science and would escape theological condemnation.” He was justified in making this statement: his model explained the apparent movement of the planets.
Geo-heliocentric model
In the geo-heliocentric model, the Moon and Sun orbit the Earth (blue orbits). The other planets that were known at that time — Mercury, Venus, Mars, Jupiter, and Saturn — revolve around the Sun (orange orbits). An observer on Earth sees the motion of the luminaries as the same in both models.
Moreover, in the majority of school work on mechanics, the local interaction of objects occurs implicitly within a frame of reference that can be considered not just a geocentric but also perfectly flat Earth, immersed in a uniform gravitational field. Thus, when solving problems about the movement of a body thrown at an angle to the horizontal, with a healthy imagination you can visualize how a projectile would fly to the edge of the Earth and fall onto an unlucky elephant…
The Wandering Center of the World
Copernicus wasn’t the first to place the Sun at the center of the universe. According to some sources, the ancient Greek astronomer and philosopher Aristarchus of Samos was the author of the heliocentric system as a mathematical model that allows one to not only explain but to also predict celestial phenomena. This information, though, is fragmentary and indirect, so it’s impossible to unconditionally attribute this accomplishment to him. What is important to note is that the model of Aristarchus of Samos yielded to the authority of Aristotle and Ptolemy, the greatest minds of ancient Greece, and was forgotten for almost 1,500 years. So, this goes to show that the truth doesn’t always conquer errors and lies.
The transition to a heliocentric picture of the world according to the scientific milieu, which would have been impossible in the early Middle Ages, coincided with a very important change in the philosophy of science: abstract metaphysics gave way to experimentation due to Galileo’s efforts. The latter eventually became the objective measure of the truth of theories, expressed in the language of mathematics.
Galileo Galilei
Laid the foundations of experimental physics and classical mechanics. Galileo is one of the founders of the principle of relativity in classical mechanics, according to which all physical processes in inertial reference frames proceed in the same way, regardless of whether the system is stationary or in a state of uniform and rectilinear motion.
Seeing is Believing (But Not Always)
The Ptolemaic model of the world is much more familiar and more evident to the ordinary Earth-dweller. Indeed, day after day, we see the Sun rise in the eastern quadrant, arc across the sky (the height of which depends on the season), and disappear beyond the horizon to the west. Repeating these observations from month to month, a more attentive colleague will notice that the Sun moves along the ecliptic, crossing the celestial equator twice a year. With the right skills, one can accurately predict eclipses, phase changes, culminations of celestial objects, and much more. And all of this is based on an incorrect theory!
The close-to-true heliocentric system is inconvenient for use in everyday life because it requires many corrections to the Earth’s orbit. A direct proof of the Copernican model was obtained only in 1728, when the astronomer James Bradley discovered and correctly interpreted aberration — the periodic “meandering” of the observable position of the stars, which occurs due to the movement of the Earth around the Sun. A century later, when the accuracy of angular magnitude increased to tenths of a second, the annual parallaxes of certain stars were measured.
Why Heliocentrism Won the Race
What a strange situation! On the one hand, we have a theory that explains most phenomena more or less satisfactorily but is erroneous nonetheless; on the other hand, we have a model that has been considered for centuries to be a geometric abstraction and has not been proven by experimentation. Why did the heliocentric model win out? First of all, it simply and elegantly untied the “Gordian Knots” of astronomy (such as the backward motion of the planets). Secondly and most importantly, the Copernican system paved the way for Newton to formulate the theory of gravity and thus erect the grand edifice of classical mechanics on which we rely to this day.
Isaac Newton
One of the creators of classical physics. Mathematically described the fundamental law of universal gravitation and the three laws of motion, which became the basis of classical mechanics.
Mechanics of Our World
To this day, you say? What about electromagnetism, thermodynamics, optics, and, ultimately, nuclear physics? After all, they have a relation to Newton’s laws at first glance. Surprisingly, they actually do — a very direct relation. Let us explain: Newtonian mechanics (the foundation of which are Newton’s three laws, the law of universal gravitation, and the laws of conservation of energy and momentum) works under “greenhouse” conditions — it needs low speeds, tangible masses, and a relatively small number of interacting objects that can be taken as points. A mechanical “performance” must take place on the stage, the acceleration of which is equal to zero, and ideally, the entire universe should follow suit. In the vast majority of cases, things are much more complicated.
Lagrange’s and Hamilton’s equations, which are mathematical interpretations of Newton’s axioms, became a way to reconcile Newtonian mechanics with the real world. They sparked the emergence of a new field of physics: analytical mechanics, which has furthered the edifice of modern physics, including those of its areas that are not closely related to mechanics. The cornerstone of statistical physics — Liouville’s theorem, which enables us to describe the behavior of systems with an arbitrary number of degrees of freedom — is a development of Lagrange-Hamilton mechanics. From analytical mechanics, Maxwell’s theory of electromagnetism, quantum mechanics, and general relativity were born.
Joseph-Louis Lagrange
Completed the mathematization of classical mechanics. He introduced generalized coordinates and developed the principle of least action.
William Hamilton
Introduced the concept of the variation principle of least action, which is used in many branches of physics. He formulated his mechanics with useful technical additions, with a deeper mathematical structure.
James Maxwell
Laid the foundations of modern classical electrodynamics (Maxwell’s equations), the kinetic theory of gases (established the distribution of gas molecules by velocities), and the quantitative theory of colors.
