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People have always wondered about the nature of matter. Did matter always exist or did it have a beginning? Is matter continuous or composed of individual atoms? Do spirits and essences cause inanimate matter and life to grow and move or is the world the result of mechanistic forces and the random movement of atoms?
Along with Hindu, Jain, and Buddhist philosophers in the first millennium BC, two Greeks, Leucippus (430 BC) and his pupil Democritus (420 BC), derived an atomic theory of matter and stated that matter is composed of “an infinite number of atoms. They move in the void and by their coming together they effect coming into being.”[1] Our word “atom” derives from the Greek word atomos, which means indivisible. Aristotle (384-322 BC) rejected the concept that matter was eternal because he viewed it as an atheistic theory. Aristotle argued that God or gods created matter and gave it a purpose. He also did not think that human life, animal life, stars, and the earth could be governed by the random movement and joining of atoms with no appointed end in view. He believed in teleology, which holds that everything has an appointed purpose or end. He also thought that matter was continuous and divided into infinitely small parts with the same properties.
There were sporadic and failed efforts to revive the theory of atomism over the next 2,000 years. The concept of atomism was tied to atheism. It first ran into opposition from Greek and Roman religions and then from Christianity. Shortly after Aristotle, Epicurus (341-270 BC) stated that atoms function and exist without control by gods or other nonmaterial forces and that all matter is composed of atoms. Lucretius (99-55 BC) stated that all events in nature were due to the random movement of atoms with no influence by the gods, and that no supernatural being made the universe. As with Epicurus, he believed that there is no life after death.
Hero of Alexandria (10-70 AD) showed that air is composed of discrete particles by inverting a glass and pressing it into a tub of water: the fact that the water did not run into the glass proved that there was something in the glass. He then inserted a hole in the glass and as he forced the glass down into the water, he could feel the air coming out of the hole. He thus reasoned that the air was composed of moving atoms. However, Aristotelian views and religious concepts dominated science and proved to be an insurmountable barrier to Hero’s theory. Although Aristotle made many important contributions to science, ethics, and philosophy, some of his incorrect conclusions about physics and cosmology, such as a geocentric universe, repressed science in these disciplines for two thousand years.
St. Thomas Aquinas popularized Aristotle’s works in the Catholic Church during the 13th century because he thought he saw in Aristotle’s works a basis for Christian theology. In historical art, Aquinas is often attributed with a divine connection that legitimized his viewpoints. In hindsight, his popularization of Aristotelian science does not appear to have been divinely inspired since Aristotle was generally incorrect. From 1200 to 1650, the universities of Western Europe based their philosophical and scientific curriculums on the works of Aristotle. [2] In contrast, the views of Epicurus and Lucretius did not receive a warm response in Catholic Europe. Poggio Braciolini (1380-1459) discovered and circulated a copy of Leucretius’ first century De Rerum Natura although it was more of an academic interest for Braciolini rather than a promotion of Lucretius’ concepts. Giordano Bruno, a Dominican monk, promoted atomism and several other nonconventional concepts, and the Inquisition burned him at the stake.
The Scientific Revolution was the key to the development of the correct theories of matter and energy. Rene Descartes and Catholic priest Pierre Gassendi successfully promoted the theory of atomism in 1649. They were successful because they conducted experiments that proved their claims. They showed that atoms combine into molecules, and atoms and molecules constitute matter. The church’s acceptance was aided by Gassendi’s claim that God made atoms in the beginning and endowed them with a certain impetus that compelled them to move until the end of time;[3] however, the major reason for their successful promotion of a theory that contradicted the conventional viewpoint was that they provided proof through experiments.
Figure 2‑2. Robert Boyle. Credit: Johann Kerseboom.
Robert Boyle (1627-1691) was the son of the richest man in England, the Earl of Cork. He lived just after Kepler discovered that mechanistic forces moved the planets, which was the impetus behind the scientific revolution. Boyle (Figure 2‑2) searched for mechanistic explanations of phenomena. He was one of the first experimentalists, and he discovered several laws of physics and chemistry through his experiments. Boyle determined through experiments that the fundamental substances were not earth, air, fire and water, as had been proposed by Aristotle. He broke down compound substances into their constituent elements in experiments and called these materials the primary substances. He used an air pump and inflatable animal lung to show that air is composed of particles (atoms and molecules) that bounce off each other and off the surfaces of containers, and that this is what causes pressure. By pumping up the lung, he developed Boyle’s Law: pressure is inversely proportional to volume.
Boyle lived in a culture that viewed all phenomena as the result of spirits, essences, and occult forces. He tried to convince people that God set up the world to operate on mechanistic principles. He wrote an important book in the field of chemistry, The Sceptical Chymist, in which he argued that everything results from collisions of particles (atomism), contradicting the views of Aristotle. Boyle believed that God still intervened in the world through miracles, but he saw them as temporary interruptions of natural processes. He was one of the founders of the Royal Society, a prestigious group of scientists that ascribed to natural philosophy (naturalism or mechanism).
Prior to the 18th century, scientists did not think that matter and energy were necessarily conserved. They thought that combustion and resultant heat was the liberation of phlogiston from the burning object. Antoine and Marie Lavoisier (1743-1794) conducted experiments that showed that the mass of chemicals is conserved during combustion and other chemical reactions. Based on the experiments, Lavoisier proposed the law of conservation of mass in 1789: “We must lay it down as an incontestable axiom, that in all the operations of art and nature, nothing is created; an equal quantity of matter exists both before and after the experiment. Upon this principle, the whole art of performing chemical experiments depends.”
Figure 2‑3. Combustion of methane (CH4) and oxygen (O2) and formation of carbon dioxide (CO2) and water. The Credit: Wikipedia, Jynto Robert A. Rohde Jacek FH Jynto
For example, the combustion of methane with oxygen forms carbon dioxide and water molecules (Figure 2‑3), conserving the number of hydrogen (white), carbon (black), and oxygen (red) atoms in the process. By this result, Lavoisier debunked the concept that Phlogiston is a substance that is released from matter during combustion. Lavoisier erroneously proposed the concept that Caloric is a gas that flows from hot to cold bodies. Scientists later discovered that energy is released during combustion due to the difference in bonding energies in oxygen and carbon dioxide (Figure 2‑3).
Many scientists in the 18th and 19th centuries contributed to the development of the law of conservation of energy, also known as the 1st law of thermodynamics. Count Rumford (1753-1814) debunked the concept of caloric. While drilling cannons, Rumford noticed that water that was used to cool the drill bit continued to boil as long as the drilling continued. Because the heat was not used up, he reasoned that heat was caused by friction from the drill bit. Thus, Rumford proposed that mechanical energy was converted to heat (energy) in the process of drilling. Based on Rumford’s and many other discoveries, James Joule (1818-1889) realized that energy is always conserved, even though it changes forms.
Figure 2‑4. First law of thermodynamics, a.k.a. conservation of energy.
The law of conservation of energy, also called the first law of thermodynamics (Figure 2‑4), states that energy can exist in many forms, but energy is always conserved and can neither be created nor destroyed. As with Rumford's cannon drilling, work (the power running the grinder) can be converted to energy and vice versa.
In the 19th century scientists discovered the laws of chemistry and the nature of the elements. John Dalton (1766 – 1844) developed the universal law of atomic theory and the law of simple multiple proportions, describing how atoms behaved in chemical reactions. He also constructed a chart of elements and molecules, based on his experiments (Figure 2‑5).
· Universal law of atomic theory
o All matter is composed of indivisible particles called atoms.
o All atoms of a given element are identical.
o Chemical reactions involve the combination of atoms, not the destruction of atoms.
· Law of simple multiple proportions
o When elements react to form compounds, they react in defined, whole number ratios.
Figure 2‑5. John Dalton and his chart of elements and molecules in Dalton's A New System of Chemical Philosophy (1808). by Thomas Phillips, National Portrait Gallery, London (1835).
Dalton determined that compound substances are composed of atoms bound together by a force of attraction He determined that all compound substances are composed of uniform proportions of elements, and he found these proportions by measuring weights of substances in chemical reactions. Thus, he was able to determine the relative masses of many elements. Although Dalton was in error about the atomic weight of some elements, his work led to the wide acceptance of the concept that matter is composed of atoms that combine to form molecules. Dalton grouped the elements into groups of similarly behaving elements (Figure 2-5).
At the time of Dalton, scientists thought that the atoms were indivisible; thus, they mistakenly called them atoms (indivisible). Dalton stated, “We might as well attempt to introduce a new planet into the solar system, or to annihilate one already in existence, as to create or destroy a particle of hydrogen.” At the beginning of the 20th century, scientists discovered that atoms are composed of smaller particles.
Mendeleev (1834-1907) (Figure 2‑6) was an amazing Russian chemist who discovered patterns among the elements and figured out a way to organize the patterns in a table. He developed the Periodic Table (Figure 2‑7) of the elements in 1869, which is an important foundation of chemistry. For example, elements in the same column in the Periodic Table behave similarly in chemical reactions. The modern version of the Periodic Table in Figure 2‑7 shows the atomic number (top whole number), symbol (letters), and atomic mass (bottom number) of each element. Mendeleev stated that he saw the Periodic Table in a dream.
Figure 2‑6. Dmitri Mendeleev. Credit: М.М.Шульца Ниной Дмитриевной Шульц. Public domain
Mendeleev stated that he saw the Periodic Table in a dream.
“I saw in a dream a table where all elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper, only in one place did a correction later seem necessary.”
The dream did not just arise out of the blue. He had made cards representing each of the elements. He worked for hours arranging and rearranging the cards in order to make a table that organized the classification of the elements, but he was unsuccessful. After he fell asleep from exhaustion, he woke up with a dream that had the correct arrangement of the cards. This sort of scientific epiphany when the mind is at rest might not be that unusual. It could have happened in the shower.
Because Mendeleev correctly arranged the cards in the Periodic Table, he was able to see that there were gaps in the table, and he was able to predict which elements scientists would soon discover.
The position of elements in the Periodic Table determines their reactions with other elements. Electronegativity is the potential of atoms to take electrons from other atoms. Elements on the right side are very electronegative, which means that they steal electrons from elements on the left side of the table. For example, sodium (Na) and potassium (K) are in the same column in the Periodic Table and react similarly. They both form salts with chlorine (Cl). Elements in the middle of the table, such as carbon (C), nitrogen (N), and oxygen (O) tend to share electrons because they are neither electropositive or electronegative.
Figure 2‑7. Modern version of the Periodic Table of the elements. Credit Department of Energy Los Alamos National Laboratory. https://www.periodic.lanl.gov/
Mendeleev’s table was the culmination of the chemical experiments of the 17th to 19th centuries. Although atoms seemed indivisible and unique, Mendeleev’s table and the corresponding properties in columns of the periodic table should have led to the realization that there were underlying properties or substances in atoms that caused atoms in similar groups to behave similarly. The underlying properties and substances would be revealed in the next great revolution in the understanding of matter.
References
References
[1] Joel Cuello, “The Descent of Biological Engineering,” International Journal of Engineering Education, 32 no. 1 (2006): 35-44.
[2] E. Grant, 1986. Science and Theology in the Middle Ages. In God and Nature. Historical Essays on the Encounter between Christianity and Science. Edited by D. Lindbergh and R. Numbers. (Berkeley: University of Californa Press, 1986), p. 52.
[3] Cuello, Descent.
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Italian fresco with laughing Democritus and crying Heraclitus. Credit: Pinacoteca de Brera (1477). Image: Bramante. Public domain.
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