Our understanding of nature and in particular the history of physics and the laws that govern it, has changed radically since the days of the ancient Greek natural philosophers, here it is explained how and why these changes occurred, through historical experiments and theories that, for their time, were revolutionary.
Origin and Evolution of Physics
According to Historical background of physics and natural philosophy, they were used interchangeably for science whose objective is the discovery and formulation of the Fundamental Forces of Nature, As the modern sciences developed and became increasingly specialized, physics came to denote that part of physical science was not included in astronomy, chemistry, geology, and engineering.
However, physics plays an important role in all of the natural sciences, and all of these fields have branches in which physical laws and measurements are given special emphasis, with names like astrophysics, geophysics, biophysics, and even psychophysics, physics can , at base, defined as the science of matter, motion, and energy, its laws generally expressed with economy and precision in the language of mathematics.
The ultimate goal of physics is to find a unified set of laws governing matter, motion, and energy at small subatomic distances, at the human scale of everyday life, and at larger distances (for example, those on the extragalactic scale). ), this ambitious goal has been largely realized.
Although a completely unified theory of physical phenomena has not yet been achieved, a remarkably small set of fundamental physical laws seems to be able to account for all known phenomena.
The body of physics developed until about the turn of the 20th century, known as classical physics, can largely explain the motions of slow-moving macroscopic objects with respect to the speed of light and for phenomena such as heat, sound, electricity, magnetism and light.
Modern developments in relativity and quantum mechanics modify these laws as they apply to higher speeds, very massive objects, and to the small elementary components of matter, such as electrons, protons, and neutrons.
Ancient Physics
Thales was the first physicist and his theories really gave the discipline its name, he believed that the world, although made of many materials, was actually built of a single element, water, called Physis in ancient Greek.
The interaction of water between the phases of solid, liquid and gas gave materials different properties, this was the first explanation to bring natural phenomena out of the realm of divine providence and the realm of natural laws and explanations.
Anaximander, most famous for his proto-evolutionary theory, disputed the ideas of Thales and proposed that instead of water, a substance called Apeiron was the building block of all matter, with the help of modern hindsight we can say that this was another Clever assumption of Anaximander and very similar to the idea that hydrogen is the building block of all matter in our universe.
One of the first renowned ancient physicists was Leucippus, who strongly opposed the idea of direct divine intervention in the universe, this philosopher instead proposed that natural phenomena had a natural cause. Leucippus and his student Democritus developed the first atomic theory, arguing that matter could not be divided indefinitely and would eventually come to individual pieces that could not be cut.
first atomic theory
It is an ancient philosophical speculation that all things can be explained by innumerable combinations of hard, small, indivisible particles of various sizes but of the same basic material or the modern scientific theory of matter according to which the chemical elements that combine to form the A great variety of substances consist of aggregations of similar subunits, which have a nuclear and electronic substructure characteristic of each element.
Euclid and mathematics
The unevenness of the various books and the varied mathematical levels may give the impression that Euclid was no more than an editor of treatises written by other mathematicians, to some extent this is true, although it is probably impossible to determine which parts are his and which were his. adaptations of its predecessors. Euclid's contemporaries considered his final and authoritative work, to say the least, to have been like commentaries on the Elements.
Aristotelian Physics
Interestingly, although Aristotle is regarded as the father of science and positively helped the Summary of the History of Physics with his systematics and practice, he actually hindered the advancement of physics through several millennia.
He himself made the mistake of saying that mathematical theory and the natural world did not overlap, a password for his overreliance on knowledge. Aristotle sought to manifest doctrines such as motion and gravity with his theory of the elements, an addition to ancient physics that also extended to alchemy and medicine.
Aristotle strongly professed that all matter was made up of a combination of five elements, earth, air, fire, water and intangible ether, he took this further by insinuating that the earth kingdom was surrounded by air, followed by the kingdoms of fire and ether.
Physics in the medieval Islamic world
Mechanics was one of the most developed sciences to be pursued in the Middle Ages, operating within a fundamentally Aristotelian framework, medieval physicists criticized and attempted to improve on many aspects of Aristotle's physics.
The problem of projectile motion was crucial to Aristotelian mechanics, and the analysis of this problem represents one of the most impressive medieval contributions to physics, due to the assumption that the continuation of motion requires the continuous action of a driving force, the continued movement of a projectile after losing contact with the projector required an explanation.
Aristotle himself had proposed explanations of the continuation of projectile motion in terms of the action of the medium, the character of these explanations making them unsatisfactory to most medieval commentators, who, however, retained the fundamental assumption that projectile motion continuous requires a continuous cause.
During the 1300s, certain Oxford scholars pondered the philosophical problem of how to describe the change that occurs when qualities increase or decrease in intensity, and came to consider the kinematic aspects of motion.
Ptolemy and the geocentric model
Also called the geocentric system, a mathematical model of the universe formulated by the astronomer and mathematician Alexandrinus Ptolemy and recorded by him in his Almagest and Planetary hypotheses, the Ptolemaic system is a geocentric cosmology, that is, it begins by assuming that the Earth is stationary and in the Center of the universe.
classical physics
Classical physics took shape when Newton raised his theory of gravity and the mathematics that we commonly know as calculus collaborated with the Historical Development of Physics, Newtonian physics was three-dimensional, width, height and depth, three hundred years ago, Isaac Newton declared that space and time are eternal and unchanging ingredients in the composition of the cosmos, pristine structures that lie beyond the limits of the question and the explanation.
Newton wrote in principle mathematics:
"Absolute space in its nature without relation to anything external is always similar and immovable, absolute, true and mathematical time of itself and its own nature flows equally without relation to anything external."
Newton's theories about the universe, although Einstein would show that they are imprecise, served science for centuries, despite their deficiencies, allowed the technological innovations of the industrial revolution, a theory is a coherent model that guides thoughts, a set of perceptions that can be modified until a better theory is advanced.
Newton's theories included his theory of gravity for which he developed calculus to describe it, his concept of three dimensions in an infinite universe, his particle theory of light, and his underlying belief embodied in his theories that, in fact, there were straight lines in nature, Newton's questions about the physics of light resulted in the particle theory of light, that is, each ray of light traveled in a straight line and had an incredibly small mass.
The Sun as the center of the universe
The ancient Greeks, for example, considered that the planets included the Sun, the Earth was at the center of everything (geocentric), with these planets revolving around it, this became so important in the culture that the days of the week carried the name of the gods, represented by these seven moving points of light.
Newton's physical laws
The links between the forces acting on a body and the body's motion, first expressed by the English physicist and mathematician Isaac Newton, according to the Isaac Newton Biography the laws of the same emerged for the first time in his work in the year 1687, which is usually known as Principia.
Scientific revolution
A new idea of nature was born in the midst of the Scientific Revolution, replacing the Greek approach that had subjugated science for many years, science became a free method, distinct from philosophy and technology, which came to be considered contained positivistic goals.
By the end of this period, it may not be too much to say that science had replaced Christianity as the focal point of European civilization, out of the ferment of the Renaissance and the Reformation a new view of science arose there, bringing about the following transformations , the re-education of common sense in favor of abstract reasoning, the substitution of a quantitative for a qualitative view of nature.
The vision of nature as a machine rather than an organism, the development of an experimental and scientific method that sought definitive answers to certain limited questions formulated within the framework of specific theories, and the acceptance of new criteria of explanation, emphasizing the «how instead of the "why" that had characterized the Aristotelian search for final causes.
Thermodynamics and Optics
If hydrodynamics or the theory of elasticity are not of immediate interest for the study of quantum theory, then with optics the situation is completely different, since its progress is closely related to the development of modern physics, similar to the phenomena that occur with solid and liquid bodies, light phenomena have also attracted people's attention since the earliest times, but only in the XNUMXth century.
Optics began to form into a real science. During this period, Descartes formulated the laws of refraction and reflection of light and Fermat proposed his principle, which contains all geometrical optics, during this entire period of the development of optics, the concept of light rays played an important role in it. , the rectilinear propagation of light rays in a vacuum or in homogeneous media, their reflection from specular surfaces, and refraction during the transition from one medium to another.
Electromagnetism and Atomic Structure
Mechanics and related fields, as well as acoustics and optics, arose a long time ago, because they study the phenomena that a person constantly encounters in his daily life, the science of electricity, on the other hand, appeared relatively recently.
Of course, some facts, such as the electrification of bodies by friction or the properties of natural magnets, were already known before, natural phenomena as majestic and strange as electrical storms cannot fail to attract attention.
However, it is unlikely that these facts were sufficiently studied and compared until the end of the XNUMXth century and almost no one clearly imagined at that time that it would become the object of study of a new science, which constitutes one of the most important areas of modern physics, this became clear only in the late XNUMXth and early XNUMXth centuries.
It is interesting to note that at the same time interference phenomena were discovered and the theory of waves was built, this remarkable period in the history of the development of science, when wave optics and the modern theory of electricity arose, was for macroscopic physics what the last 50 years were for atomic physics.
Modern physics
Modern physics often involves an advanced description of nature through new theories that were different from classical descriptions and involves elements of quantum mechanics and Einstein's relativity, for example quantum effects typically involve distances related to atoms , on the other hand, relativistic effects generally involve speeds compared to the speed of light.
Energy
Physicists use the term energy to denote the ability to change state or to produce work that causes motion or generates electromagnetic radiation, for example, from light or heat, the word comes from the Greek and means "force in action."
In the international system, energy is expressed in joules, but in common terms, it is most often expressed in kilowatt-hours (kWh), as for the ton of oil equivalent (toe), it generally allows the different sources to be compared. of energy from each other, it should be noted that, according to the first law of thermodynamics, the energy of a closed system is conserved.
Thermodynamics
It is based on the first and second law, that is, the conservation of energy and the increase of entropy, these laws impose strong restrictions on any model of the universe, in addition, some properties of space and time are emerging in a thermodynamic sense .
Therefore, these notions should not be considered as basic structures of fundamental interactions, in this sense, space-time es thermodynamic, moreover, if one accepts to incorporate statistical arguments, one must ask if the forces of the universe are perhaps thermodynamic, our universe would thus be governed by entropic forces rather than by absolute forces.
Electromagnetism
They are based on Maxwell's wave theory and its equations, but are much less well understood than these theories, not based on his initial interpretation of the relationship between the E and B fields, but on Ludvig Lorenz's, with which Maxwell did not agree.
Maxwell thought that these two fields should be induced cyclically so that the speed of light is preserved, unlike Lorenz, who thought that both fields should obtain their maximum intensity synchronously at the same time to maintain that speed, the equations allowing both paraphrases.
Quantum mechanics
The quantum world of atoms and subatomic particles is wonderful, a single particle can behave as if it were in two places at once and a pair of particles, at opposite ends of the universe, can somehow behave as a single entity.
While it may seem impossible to wrap our minds in so much quantum weirdness, this sequence of lectures goes a long way toward demystifying the quantum world, giving us solid insights into the fascinating "cogs and wheels" of how atoms work.
Big Bang
In the first second of the universe's existence, our understanding of what was happening is surprisingly good. We know that the concepts of time, space and the laws of physics solidified very quickly, from there, order began to emerge from chaos, the first to take shape were subatomic particles such as quarks.
Then larger particles like protons and neutrons, about three minutes later the universe had cooled to a billion °C. This allowed protons and neutrons to come together through fusion and form nuclei, the charged nuclei of atoms .
Relativity
The far-reaching physical theories developed by the German physicist Albert Einstein, with his theories of special relativity in 1905 and general relativity, Einstein put aside many comments on previous physical theories, working in the process on the fundamental concepts of space, time, matter, energy and gravity.
Nuclear physics
This branch of physics deals with the structure of the atomic nucleus and the radiation of unstable nuclei.
the energy of the atom
Like excited atoms, unstable radioactive nuclei (naturally produced or artificially produced) can emit electromagnetic radiation, the energetic nuclear photons are called gamma rays. Radioactive nuclei also emit other particles, negative and positive electrons (beta rays), accompanied by neutrinos and helium nuclei (alpha rays).
Forces inside the nucleus
In radioactivity and in collisions leading to nuclear breakdown, the chemical identity of the nuclear target is altered whenever there is a change in nuclear charge, in nuclear fission and fusion reactions in which unstable nuclei split, respectively, into smaller nuclei or amalgamate into larger nuclei, the energy release is much greater than that of any chemical reaction.
Recent advances in physics
In recent years there have been discoveries that allow an advance in physics, such as those detailed below:
She is
The laser would not have been possible without knowing that light is a representation of electromagnetic radiation. Max Planck received the Nobel Prize in Physics for his discovery of elementary energy quanta, as in the Quantum Planck Theory he was working on thermodynamics, wanting to show why "blackbody" radiation, something that soaks up all wavelengths of light, didn't radiate all repeats of light equally when irritated.
The Large Hadron Collider
Ten years after the start of operations of the Large Hadron Collider, one of the most complicated devices ever seen, it is the largest particle pedal in the world, buried 100 meters under the French and Swiss field with a circle of 17 miles .