Unit 2 Lesson 1
Introduction
Physics is the science that studies the properties of matter and energy and establishes the laws that explain natural phenomena. Coming to understand how the world and nature works has been a desire that has accompanied man since time immemorial. Science is born when a rational explanation for phenomena is sought and not just a religious justification (it is the gods or spirits that govern nature). Thus, throughout history there have been great thinkers and philosophers who have created different theories to explain the world in which we live, for example, in Greece Leucippus or Democritus proposed their theories
Classical physics
Classical physics owes its development to two great scientists: The first Galileo Galilei who conducted experiments from a tower to conclude that two objects fall at the same speed, regardless of their weight. In this way he modeled a way of doing science based on the scientific method. Years later, Sir Isaac Newton was able to mathematically define the behavior of objects and thus create the laws of physics that we use today, with which it is possible to calculate a structure, or predict the parabolic trajectory of an object or even the movement of the planets around the Sun. Analytic geometry allows us to describe the trajectories of objects and the magnitude of forces by means of vectors represented, either in a two-dimensional plane, or in three-dimensional space. To calculate the paths of the planets in the solar system, Isaac Newton needed to create a new branch of mathematics called differential calculus.
His new theories were reflected in his book Philosophiæ naturalis principia mathematica, which literally means: Philosophy of nature based on mathematical principles. It is noteworthy that the great genius also wrote important treatises on optics and the nature of light. And we must not forget that Newton was fascinated throughout his life by esoteric sciences such as the Kabbalah, astrology; and in general the ancient texts, the meticulous study of which he devoted much of his time to.
For several centuries the works of Isaac Newton marked the way in which the reality in which we live was understood. To simplify, we will say that the world was understood to be basically made up of particles or corpuscles, which could be understood by applying the laws described by Newton. Also the behavior of liquids and gases could be understood as small particles subject to well-known laws. As chemistry advanced, elements could also be understood as small particles interacting to create various compounds. This is what we can call the corpuscular theory. This vision allows us to explain each phenomenon of the universe, from atoms, living organisms, to planets and galaxies.
According to this theory, the solar system can be understood as a clockwork mechanism, just like the human body or any other living being. The universe itself can be understood as a gigantic mechanism that can be understood, and its future state can be predicted by applying the already known laws of mechanics. So this approach based on physics and the mechanical effects of particles is also called the mechanistic model of the universe. It is also important to underline that according to this approach, having the necessary data it is possible to determine the future result in any system. This is possible, since, ultimately, from atoms, liquids or planets, they are all particles whose trajectories and interactions can be determined.
The whole universe is like a pool table in which the balls will follow perfectly definable trajectories that we can calculate and determine, based on the initial stimulus. It is what we call a deterministic view of the universe, everything obeys perfectly defined laws, so the future state of a system, or of the universe itself, could be determined in advance.
Electromagnetic fields
The phenomenon of electricity and magnetism brought a new concept that no longer fit the corpuscular materialist model. Electricity and magnetism can only be described by a force field that can no longer be represented by corpuscles. The field simply exists in space, without there needing to be any object of which it is composed. In any case we can speak of force or energy, but no longer of matter. By bringing a magnet closer to another, we can feel its repulsive or attractive energy, depending on the polarity, and we understand that there is a force between both objects, but we do not see an exchange of matter.
It was in the 19th century that the great Scottish physicist and mathematician James Clerk Maxwell formulated the equations to describe magnetic waves. In this way he was able to conclude that both electricity, magnetism and light obey the same phenomenon called electromagnetic waves. This is how matter began to lose prominence and energy began to gain more importance. Scientists began to discover that the world is not only made up of particles, but that energy plays a very important role. Finally, Albert Einstein discovered that matter is nothing more than condensed energy and that it can even be released obtaining large amounts of energy, according to his famous formula: E = mc2.
What is the universe made of?
As a child I once took a napkin and started to fold it in half and split it, then I took one half and in turn folded it and split it in half. I did this several times until I reached a size where it was impossible for me to manipulate the small pieces of paper, but my mind suspected that I could keep getting napkin halves over and over and over again... But how far can you divide? The matter? This questioning had already been done by several ancient philosophers such as Kanada in ancient India or Democritus in Greece. This is how the idea arose that all matter was made up of tiny indivisible units: atoms.
Chemistry, when studying the different elements, realized that each one is made up of small particles exactly the same as those called atoms, since they fit the concept of the ancient philosophers. Thus we know that the hydrogen atom, for example, is made up of a proton and a neutron in the nucleus, and has an electron in its first orbit. The helium atom already has two protons and two electrons. Lithium has 3 protons, neutrons and electrons.
Anyway, we can continue like this until we reach Nobelium with 102 electrons, the latter is a synthetic element, that is, created artificially in 1966, therefore it is an unstable element.
And since we are talking about unstable elements, this means that the atom, apparently indestructible, can finally be divided into smaller components. Nobelium, as well as other synthetic elements, can only remain stable for short periods of time, which can be from a few thousand years (a short time in relation to the age of the universe) to fractions of a second. When they decompose, they can be converted into lighter elements and can also generate radiation, as is the case with plutonium, uranium or radium.
We now know that atoms are made up of smaller particles called elementary particles, such as:
- Neutron, is located in the atomic nucleus and has no electrical charge.
- Proton, is in the nucleus of the atom, positive charge and considerable mass.
- Electron, revolves in orbit around the atomic nucleus, has a negative charge and a tiny mass, almost negligible.
In some way we can imagine the atom as a small planetary system; in fact, at first physicists thought that it was something very similar, but over time they have come to the conclusion that, in reality, they are not very similar, as we will explain in the next lesson.
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