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Our journey commences in ancient times, where the seeds of astrophysics were sown amidst the fertile intellectual landscapes of early civilizations such as ancient Mesopotamia, Egypt, China and Greece to name a few. Among the pioneers of this era were Democritus of Thrace born in the 5th Century BCE, whose revolutionary atomic theory posited that all matter consisted of indivisible particles called atoms. Although his ideas primarily pertained to terrestrial phenomena, it laid a foundational framework for understanding the fundamental building blocks of the universe.
Another luminary of antiquity was Aristarchus of Samos, whose heliocentric model challenged the prevailing geocentric, (Earth centric), worldview. In the 3rd century BCE, Aristarchus proposed that the Earth and other planets orbited the Sun—a concept far ahead of its time. Despite facing resistance from contemporaries such as Aristotle, Aristarchus’s visionary insight foreshadowed the Copernican revolution millennia later. Additionally, he calculated and estimated the distance to the Moon and the Sun and size of the Sun. It was after realizing the Sun was far larger than Earth he concluded that the Earth and other planets orbited the Sun.
Eratosthenes of Cyrene emerges as yet another luminary of antiquity, renowned for his groundbreaking contributions to geometry, astronomy and mathematics. In the 3rd century BCE, Eratosthenes accurately calculated the circumference of the Earth using simple trigonometric principles, and calculated the Earth’s axial tilt. In addition, Eratosthenes also worked on calculating the distance to the Moon and Sun as well as the diameter of the Sun adding to the works of Aristarchus of Samos – showcasing the ancient world’s nascent grasp of celestial mechanics.
Renaissance
As the world transitioned into the Renaissance period, the torch of astrophysical inquiry continued to burn brightly in the hands of visionaries such as Nicolaus Copernicus. Building upon the heliocentric model proposed by Aristarchus, Copernicus’s seminal work “De Revolutionibus Orbium Coelestium”, (On the Revolutions of the Celestial Spheres), revolutionized our understanding of the solar system. Thereby, placing the Sun at the center of the cosmos, Copernicus catalyzed a paradigm shift that would forever alter humanity’s perception of its place in the universe.
The Enlightenment era ushered in a golden age of scientific discovery, with luminaries such as Johannes Kepler and Galileo Galilei making indelible contributions to astrophysics / astronomy. Kepler’s laws of planetary motion provided a mathematical framework for understanding the dynamics of celestial bodies, while Galileo’s telescopic observations offered compelling evidence in support of the heliocentric model.
20th century
The dawn of the 20th century witnessed the birth of modern astrophysics / astronomy marked by transformative developments in theoretical physics and observational techniques. Albert Einstein’s theory of general relativity completely changed our understanding of gravity, by adding to Isaac Newton findings, Einstein’s work offered profound insight into the curvature of space-time and the behavior of massive objects in the cosmos. Meanwhile, advancements in spectroscopy and telescopic technology facilitated unprecedented discoveries, allowing astronomers to peer deeper into the universe than ever before.
The latter half of the 20th century witnessed a surge in astrophysical / astronomical research, fueled by technological innovations such as space-based observatories and supercomputers. The advent of radio, X-ray and Gamma astronomy opened new vistas of exploration, enabling scientists to study cosmic phenomena beyond the visible spectrum. Concurrently, the emergence of particle astrophysics shed light on the enigmatic nature of dark matter and dark energy—two elusive entities that comprise the majority of the universe’s mass-energy content.
In recent decades, the field of astrophysics has witnessed a convergence of disciplines, as researchers unravel the mysteries of black holes, gravitational waves, and the cosmic microwave background, (CMBR). Groundbreaking discoveries such as the detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) have provided empirical validation for Einstein’s predictions, while opening new avenues for studying the dynamics of space-time.
As we stand on the precipice of a new era of exploration, the future of astrophysics / astronomy appears more promising and tantalizing than ever before. From the quest to uncover the origins of cosmic inflation to the search for extraterrestrial life, humanity’s insatiable curiosity continues to drive scientific inquiry to unprecedented heights. As we gaze upon the vast expanse of the cosmos, we are reminded of our shared quest to unravel the mysteries of existence and unlock the secrets of the universe.
In perspective
In retracing the illustrious history of astrophysics / astronomy, we are reminded of humanity’s enduring quest for knowledge and understanding. From the ancient musings of Democritus and Aristarchus to the groundbreaking discoveries of modern-day physicists, the journey of astrophysics serves as proof to the boundless potential of the human intellect. Gazing upon celestial weave of the cosmos, humans are reminded of our humble place within the vast expanse of space and time—a reminder of the profound interconnectedness that binds us to the universe itself.
I should add that amateur astronomers are now playing an increasingly active role in cosmic research, a number of projects are currently running that actively engage amateur astronomers to aid in the searching of the cosmos.
The vast expanse of the cosmos means it is impossible to observe the whole universe all the time, therefore, by engaging experienced home based astronomers across the globe it allows more of the cosmos to be observed, thus providing researchers with extra eyes to report possible finds.
Amateur astronomy is currently one of the fastest growing pastimes, as a professional astrophysicist I actively encourage everyone to look skyward and explore the cosmos either for pure pleasure and wonder or with the aim of possible becoming engaged in a live project.
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Special notes:
Size of the observable universe
The observable universe is more than 46 billion light-years in any direction from Earth, therefore, the observable universe is 93 billion light-years in diameter. Given the constant expansion of the universe, the observable universe expands another light-year every Earth year. However, it is important to note this is only the observable universe and Earth is simply part of the universe and not at the center of the universe.
One light year is equivalent to 9.46 trillion kilometers.
Point of interest:
Recent ground breaking research has identified evidence that suggests black holes are the source of dark energy, however, it must be remembered that this research is in the early stages and required more work.
Although, other researchers have proposed sources for dark energy, what makes this research unique is this is the first observational research where nothing was added to explain the source of dark energy in the Universe. This research simply uses existing proven physics, in other words black holes in Einstein’s theory of gravity are the dark energy.
As further research is carried out and empirical testing hopefully provides the same answers then the mystery of the source for dark energy with be known at last, resolving a physics conundrum.
Theory of general relativity
A simple summing up of the core principles of general relativity.
John Wheeler, theoretical physicist, summed up the core of Albert Einstein’s theory of general relativity. “Matter tells space-time how to curve, and curved space-time tells matter how to move”.