Physics and Astrophysics

Glimpses of the Progress

Subal Kar

• Publisher: CRC Press
• Year: 2022
• Print ISBN:
  9781032105277
• eBook ISBN:
  9781000559262
• Topic: Physical Sciences
• Subtopic: Astronomy & Astrophysics

Physics and Astrophysics—Glimpses of the Progress provides a comprehensive account of physics and astrophysics from the time of Aristotle to the modern era of Stephen Hawking and beyond. It takes the readers of all ages through a pleasant journey touching on the major discoveries and inventions that have taken place in both the macro-world, including that in the cosmos, and the micro-world of atomic and subatomic particles related to physics and astrophysics. Use of historical perspective and anecdote makes the storytelling on the progress of physics and astrophysics both interesting and absorbing. While peering through different developments in these fields, the book never compromises with the sanctity of the scientific content, including the depth and beauty of the physical concept of the topics concerned and the philosophical viewpoints they represent. Where appropriate, the book also delves into value judgments of life that affect our civilization.

Features

• The intricate concepts of physics and astrophysics are explained in simple terms and in easy-to-understand language.

• Physics and astrophysics are discussed in a connected and correlated way in a single volume of comprehensive size but in totality, which to date is the unique feature of this book.

• Starting with Aristotle's Physics and going through the work of Newton, Einstein, Schrödinger, Hubble, Hewish, Hawking, and others, including the present research on dark energy, dark matter, and the fifth force of nature, the reader will be kept absorbed and spellbound.

• In addition to the fundamental principles of Newtonian mechanics, Einstein's relativity, quantum mechanics, string theory, loop quantum gravity, and so on, the cutting-edge technologies of recent times, such as the Large Hadron Collider, Laser Interferometer Gravitational-wave Observatory, and Event Horizon Telescope, are also explored.

The book is aimed primarily at undergraduate and graduate students, researchers, and professionals studying physics and astrophysics. General readers will also find the book useful to quench their thirst for knowledge about the developments in physics and astrophysics.

1The Beginning: Physics and Astrophysics from Ancient Times to the End of the 19th Century

DOI: 10.1201/9781003215721-1

Everything that exists had a beginning

1.1 Introduction

From ancient times, the human mind has been haunted by many fundamental questions. When did the universe start and how? What is its structure? Does the universe have a boundary? Who created it? Will it die? Such questions have been addressed throughout the ages in different ways by both mystics and scientists all over the world. The journey is still continuing at a full and even increased pace, especially by scientists. Our thirst for such knowledge has been quenched to some extent over the ages, but it appears that we are still at the tip of the iceberg and we have a long way to go. Perhaps the eternal joy of the thinking mind of humankind lies in journeying through such a never-ending path of endeavor in the quest for knowledge. In the words of the great American poet, Robert Frost: “And miles to go before I sleep, And miles to go before I sleep.”

Knowledge is a process of an ever-widening horizon as we step through the stairs of vision and reason, which help us breathe the refreshing air of satisfaction that comes with leaping forward. Peter J. Ratcliffe, Nobel Laureate of medicine in 2019, made a simple but thoughtful comment: “Knowledge builds on knowledge.” Isaac Newton's famous statement, “If I have seen further it is by standing on the shoulders of Giants,” is worth mentioning here. In fact, our knowledge about everything that we see around us has developed exactly that way. Also, that our knowledge about anything is increasing means that the difference between the “knowable” and “earned knowledge” is decreasing. However, the knowable is literally infinite; thus, our journey in the thirst for knowledge continues—and probably will continue forever. One of my revered teachers in my college days asked me: “Can you tell me, Subal, what is the quotient between what I know and what I do not know?” Noting my silence and the inquisitiveness in my eyes, seeking for an answer, he politely but confidently answered: “It's a Big Zero.” Now, I realize that this remark reflected not his modesty, but his honesty from the core of his heart as a great teacher. Here we can also call to mind Socrates' famous quote: “The only true wisdom is knowing you know nothing.”

“Nature permits and Nature prohibits—you just have to understand the limits set by her.” Herein lies the true knowledge, the meaningful realization of truth. If you understand this coded language of Mother Nature, you will be the master of philosophy, of the arts, of science—a “great master” true to its sense. Any great discovery of science is dependent on nature's permission and prohibition: Nothing is all encompassing. Certain aspects of nature have evolved into a particular discovery, but certain other aspects are yet to be unveiled. The journey of knowledge thus proceeds with this possibly never-ending filling-of-the-gaps. This dalliance of Mother Nature is applicable to philosophy and the arts too, but science differs from other branches of knowledge because its permission and prohibition are to be established further by experimental verification. Since ancient times, knowledge of the unknown has taken us from the illusion of obscurity to the effulgence of reality, guided by the rational thinking and the realism of our journey through science.

Throughout the ages, thinkers have asked themselves this question: “What is reality?” They have produced a fascinating spectrum of responses. Is there more to reality than meets the vision of our bare eyes? “Yes,” was Plato's answer over two millennia ago. According to Plato, what we humans call our everyday reality is just a limited and distorted (in Indian terms “illusive”) representation of the true reality, and so we must free ourselves from our mental shackles to begin comprehending it. The most important lesson that modern physics has taught us about the ultimate nature of reality is that whatever it is, it is very different from what it seems to our gross sense perceptions. We have to use our scientific acumen to understand the reality with a sublime philosophical vision in order to visualize the true nature of reality. Thus, our journey in this book, while coursing through the fascinating history of the development of physics and astrophysics, is from the obscurity of our gross views obtained through our bare eyes of common sense to the effulgence of the finer understanding of the true nature of reality in terms of the objectivity of science and technology.

1.2 Physics and Astrophysics Developments from Ancient Times to Galileo

1.2.1 Introduction

If we go back some 2,620 years, say 600 B.C., Earth was known to humankind as just a patch of flat ground (as it indeed appears to be our gross vision through our eyes, barring the minor irregularities of the mountains and valleys). The sky overhead was known to hold the Earth—with tiny luminous objects (stars and planets) shining in it and two large disc-shaped shiny objects, one of which was visible in the day (the Sun) and the other at night (the Moon). The Earth was believed to be at the center of the universe, with the Sun, Moon, and others revolving around it.

1.2.2 Motion of Bodies and Miscellaneous Ancient Thoughts

The first systematic knowledge book of science known to us is Physics, written by Aristotle, the great Greek philosopher, scientist, and resident teacher of Alexander the Great. The book was not named after the discipline we now know as physics, but the said discipline received its name from Aristotle's book. Aristotle believed in two motions on the Earth—forced motion and natural motion. Forced motion was believed to be caused by a thrust or impulse and to end when the thrust/impulse ended. For example, a football moves when it is kicked, a breeze causes the branches of a tree to swing, a boat moves by itself (without being rowed) when placed in a flowing river—in all these cases, the thrust comes from leg, wind, and stream, respectively. The natural motion according to Aristotle is vertical—upward or downward. To throw a stone upward, one has to give it an upward thrust (force), and so it returns to Earth because, according to Aristotle, it wants to return to its natural level. All these accounts of the physical behavior of a body's motion on Earth given by Aristotle's physics may be a gross view, with only an approximate qualitative picture of the phenomena—which demanded significant correction as a result of the subsequent evolution of the knowledge domain of the subject of physics. But we cannot bluntly call them wrong—those were the seeds of rational thoughts. Even the physics of Newton later needed corrections in view of Einstein's theory of general relativity. Einstein's theory in turn failed near the singularity inside a black hole and needed a new set of laws called quantum gravity. Probably everything that we know today might one day be proved to be approximate or might need correction in the light of new concepts that might emerge with better understanding of physical phenomena. On the other hand, it may well be that Newton and Einstein will forever remain with us. There could be minor/major modifications of their theories as the evolution of knowledge demands, but the basic beauty, depth, and encompassing charm of their discoveries may well remain timeless for the inquisitive mind. The two basic questions that have forever changed the world of knowledge about the universe (in terms of classical physics) are: If the apple falls, does the moon also fall? (Newton) and What would happen if I rode a beam of light? (Einstein).

In addition to Aristotle, we must of course consider another great Greek thinker, Plato, disciple of Socrates and teacher of Aristotle. He understood from the works of Pythagoras, his predecessor famous for his theorem on triangles (taught in school days), that “mathematics (especially geometry) is the language best adapted to visualize the phenomena in the world around.” Plato carved in the door of his school: “let not anyone enter here who is ignorant of geometry.” Plato posed this momentous question to his disciples: “is it possible to find a mathematics that is able to describe and predict the movements of the planets” (the word “planet” means wanderer in Greek). Venus (the morning/evening star), Mars (the red planet), and Jupiter (the yellow planet) can be easily seen in the night sky, and their movements are little random, back and forth, among the other stars. In this connection, a comment from Galileo Galilei's The Assayer (1623) is in order: “Philosophy is written in this grand book, the universe, which stands continually open to our gaze. But the book cannot be understood unless one first learns to comprehend the language and read the characters in which it is written. It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures without which it is humanly impossible to understand a single word of it; without these one is wandering in a dark labyrinth.”

Plato's analytical approach to scientific phenomena ultimately gifted humankind, after a few centuries' journeys by various astronomers like Aristarchus and Hipparchus, the famous book Almagest (in 135 A.D.), written by the Egyptian astronomer Claudius Ptolemaeus (known in the West as Ptolemy). In his book Almagest, Ptolemy summarized the results of work by the Greek astronomers in a masterly way.

From Pythagoras to Plato, including Neo-Platonism, thinkers in Greece and in Europe, in general, were very much influenced by the rich and highly developed spiritual wisdom as well as the scientific developments (especially in mathematics, medicine, and astronomy) of ancient India. The so-called Arabic numerals, the decimal system, the place value system for numerals, the use of zero, and the fundamental principles of algebra and geometry are distinctly of Indian origin and were carried to Europe by the Arabs. A few famous Indian mathematicians from ancient times were A¯ryabhat.a, Bra¯hmagupta, Baudha¯yana, and S´rīdhara¯ca¯ryya, while among the modern Indian mathematicians we may name Srinivasa Ramanujan, famous for his contribution to number theory and infinite series. All of us are familiar with the Pythagorean theorem of geometry: “the sum of the squares on the legs of a right triangle is equal to the square on the hypotenuse.” However, it is believed that Pythagoras came in touch with Brahmins in Persia, if not in India; and that has been confirmed by the German Indologist, Max Müller. Pythagoras possibly learned from Indian thought the 47th theorem of Euclidian geometry, which is found in the S´ulbasûtra of Baudha¯yana (800 B.C.). Leopold Van Schroeder, also a German Indologist, states that “the Pytogorous theorem had its origin in S´ulbasûtra of Baudha¯yana and Apastamba.”

It is further believed that Pythagoras received his ideas regarding the science of music, the importance of numbers, and the existence of the fifth element from ancient Indian thought, all of which were then unknown in Greece and Egypt. In addition, Edward Royle, the British historian, feels that Hippocrates, the father of Western medicine, may have been indebted to India while writing his Materia Medica. As Royle notes, “we accepted the fundamental principles of medicine from Hindus.” In the time of Alexander, “Hindu physicians and surgeons enjoyed a well-earned reputation for superior knowledge and skill.” That India is “a parent civilization” is boldly declared by the French thinker Voltaire: “Everything came to us from the banks of the Ganges where the first Greeks traveled for nothing but knowledge.” The supremacy of ancient Indian science over that of the rest of the world gradually started diminishing as the spirituality of mystics having higher strength and practice all over India in subsequent centuries started to assume the forefront in the journey of Indian civilization. From the time of Pythagoras and Democritus in Greece, India's science and philosophy filtered through Persia to Greece and even with the presence of Brahmins from India to Greece and visits of Grecian to India. In this way, Greece gradually started to become the cradle of metaphysics and science, and eventually formed the foundation of modern science in the Western world, while India shone as the spiritual mother of humankind.

1.2.3 The Static Earth Concept

Most ancient thought revolved around a very common (basically gross) observation that the Earth was static, while the Sun, Moon, and other planets went around the Earth, with innumerable little twinkling stars in the sky above, beyond which was possibly “The Heaven.” Such thoughts were also prevalent with the Greeks, including Aristotle and Ptolemy. All the celestial bodies were supposed to move in the “void” with respect to time. Such fixed thoughts reigned supreme in ancient times and continued for a very long period of time thereafter, perhaps because they were also supported by the religious scriptures of ancient religions such as the Hindus and Hebrews.

Ptolemy elaborated on Aristotle's static Earth idea to a complete cosmological model of his time in which he assumed that Earth was fixed at the center of the universe surrounded by eight spheres of the Moon, the Sun, and five planets (Mercury, Venus, Mars, Jupiter, and Saturn) known at that time, as well as the stars (which apparently remain fixed relative to each other but rotate together across the sky), as shown in Fig. 1.1. What lies beyond that “observable universe” was not specifically mentioned, but in mystical terms in many parts of the world it was believed that beyond lay what was supposedly Heaven, the abode of the gods.

FIGURE 1.1

Representative diagram showing Ptolemy's geocentric model of the universe.

1.2.4 Geocentric to Heliocentric

We humans have long had a tendency toward hubris, arrogantly imagining ourselves at center stage, with everything revolving around us. But we have repeatedly been proven wrong. In reality, it is we who are revolving around the Sun, which is itself (including all stars in our galaxy) revolving around the center of our own Milky Way galaxy and so forth. Modern astronomical observation shows that the Earth orbits around the Sun, with a relative velocity of 29.8 km/s, and the Sun ...

Table of contents

• Cover Page
• Half Title Page
• Title Page
• Copyright Page
• Dedication
• Contents
• Foreword
• Preface
• Author Bio
• 1. The Beginning: Physics and Astrophysics from Ancient Times to the End of the 19th Century
• 2. The Golden Period: Two Master Strokes of the 20th Century—Relativity and Quantum Mechanics
• 3. Miscellaneous Developments: In the Realm of and Beyond Relativity and Quantum Mechanics
• 4. Zooming into the Subatomic World of Atomic Physics
• 5. Zooming Out to the Cosmic World of Astrophysics
• Appendix I
• Appendix II
• Copyright Acknowledgements
• Further Readings
• Subject Index
• Scientist Index