About

This blog covers scientific advances from the 18th century to the early 20th century, mainly related to college-level physics. In addition to physics, though, there are two essays on biology (“Origin of Life on Earth” and “Cellular Neuroscience”), a short essay on “Organ Physiology” for high school students, and one on human “Motivation and Reaction”.

Physics: Overview through most of the last century

Early observations and explanations of planetary motion were pivotal in developing an understanding of physics. Due to crude instruments and incomplete understanding of physical laws, it was initially uncertain whether the sun or Earth held the central position. Some scholars hypothesized that the sun was the center of our planetary system.

Nicolaus Copernicus, a well-educated Polish scholar, lawyer, mathematician, and canon of the Roman Catholic church, was one of those who early-on proposed a heliocentric system. His full theory was published posthumously, though some parts were released during his life.

Careful observations were necessary for this truth to be verified. Danish nobleman Tycho Brahe built an advanced observatory with royal funds and meticulously recorded planetary movements. After Brahe’s premature death, his assistant Johannes Kepler used these observations to confidently place the sun at the center of the planetary system. Kepler established that planets follow elliptical paths, sweeping equal areas in equal times, and he related orbital periods to the orbit dimensions.

The Italian polymath Galileo Galilei, a predecessor to Isaac Newton, clashed with the Roman Catholic Church by asserting that the sun, not the Earth, was at the center of God’s creation. As a result, and fortunate for him, he faced only house arrest and a forced repentance.

Isaac Newton, one of the greatest physicists, introduced calculus in England—a mathematical tool also developed by the German polymath Leibniz. Calculus was crucial for understanding velocity, acceleration, and planetary motion. Newton’s theories on motion prevailed until Einstein’s re-imagination of space and time in the twentieth century.

Things Both Seen and Unseen

Electrical Charge: Electrical power and electronic communication have become commonplace in the 21st century, enabling cell phones, radios, televisions, lighting, and digital memory. The history of electrical power began with the simple observation that rubbing together two substances (wool and amber, for example) could produce an electrical charge. Charges will attract or repel each other, depending on the way they are generated. It was soon discovered that charge could be positive or negative. Coulomb’s law states that the force between two charges is inversely proportional to the square of the distance between them.

Magnetism: A steady source of electric current, a battery (then called a “Voltaic pile”), was crucial for developing an understanding of magnetism. Electromagnets, which require a steady current, were introduced by Ampere in 1820. He demonstrated that magnetic fields result from moving electrical charges. Faraday, Ampere, Oersted, and Sturgeon also showed the converse: that changing magnetic fields induce electrical currents.

Light: James Clerk Maxwell formulated equations based on the observations of these men and using his equations predicted electromagnetic radiation (light) and calculated its speed using only two fixed constants, the permittivity and permeability of the vacuum. His work helped lay the foundation for relativity theory, a quarter century later.

Maxwell, Boltzmann, Gibbs, and Bohr made other significant contributions to chemistry, molecular motion, entropy, and modern physics, further expanding our knowledge of the unseen properties of our universe.

Things unseen

The realm of modern physics: Quantum Mechanics began with J. J. Thompson’s experiments on electron beams. Electrons, often called “pseudo-particles,” exhibit wave-like characteristics as proposed by de Broglie. Bohr’s explanation of the hydrogen atom’s emission spectrum and de Broglie’s wave description advanced the understanding of quantum mechanics.

Rutherford postulated that most of the atomic mass and positive charge reside in a small nucleus at the atom’s core. Schrodinger’s equation described the wave nature of electrons, while the inherent uncertainty in quantum mechanics was expressed in the Heisenberg uncertainty principle.

Relativity Theory: This concept, primarily discovered by Einstein with contributions from Lorentz, Poincaré, and Minkowski is founded on the seemingly straightforward postulate that the speed of light remains constant across all frames of reference, whether they are in steady motion (special relativity) or accelerating (general relativity). Relativity theory has significantly enhanced our comprehension of the universe.

Biology : Overview of selected topics

Cellular neuroscience is a small but important subset of biology. It examines the cellular basis and intercellular connections of the nervous system.

Organ physiology concerns the heart, lung, kidneys, among other organs and their roles in body homeostasis. This essay is written for high school students who might be considering a career in health.

Origin of life on earth examines the unanswered question of how life first began on Earth.

The human motivation and reaction essay is a brief look into what ancient and modern scholars have written about the human condition.

Finaly, an essay on How do we view our location in the universe looks at some modern astrophysical observations. All agree that the universe is immense. Astronomers estimate that there are billions of galaxies akin to our Milky Way. Each one is unique, they vary in size, and each contains billions of stars. Our Sun is but one of the stars within the Milky Way galaxy, and Earth is one of eight or nine planets orbiting our star. As we contemplate the vastness of the universe, a question arises, which is of astronomy and philosophy: is our location—or that of our Sun or galaxy—closer to the center of the universe or nearer its edge? Current understanding may seem surprising, for our location seems to be both at the center and at the edge of the universe.

About the author I attained bachelor’s degrees in physics and mathematics from the University of North Carolina, Chapel Hill, in 1968. Following two years of military service, I earned a master’s degree in physics from the University of Maryland, College Park, in 1972, and subsequently received a PhD in biophysics from the University of Maryland, Baltimore, in 1977. After completing postdoctoral work at the University of Maryland, Baltimore and Washington University, St. Louis, I taught physiology and neuroscience to first-year medical students and allied health students at the Emory University School of Medicine, Atlanta, where I conducted research in cellular neuroscience until retirement in 2011.

Acknowledgements: I extend my gratitude to my wife, Jan Abercrombie, my friend, Charlie Harris, and my nephew, Sam Solomon, for their assistance in editing these essays. Additionally, I thank Sam for his efforts in making them accessible online. It is my hope that these essays will provide valuable insights and provoke thought among students with similar interests.