À la "Flashback" 03 Trivia Quiz

Thales of Miletus, an ancient Greek philosopher and astronomer, is credited with predicting a solar eclipse that occurred on May 28, 585 BC. This prediction is a significant event in the timeline of astronomy because it marks one of the earliest instances of using scientific principles to forecast a celestial event.

The importance of Thales' prediction lies in its demonstration of the potential for human understanding and prediction of natural phenomena based on observation and reasoning. One might say that this was the birth of astrophysics. This event is often considered a milestone in the history of science because it moved away from supernatural explanations for celestial events and towards a more systematic and empirical approach.

Thales' successful prediction of the eclipse may also have had political repercussions. It has been reported that it ended a battle between the Lydians and the Medes, as both sides interpreted the eclipse as an omen and chose to negotiate peace. This historical anecdote highlights the significance of astronomical events in ancient times, and the lack of understanding by the masses.

Hipparchus of Nicaea, an ancient Greek astronomer, created one of the first comprehensive star charts around 130 BC. This work is a significant event in the timeline of astronomy due to its pioneering nature and its impact on the field.

The star chart compiled by Hipparchus listed approximately 850 stars, documenting their positions and brightness. This achievement was groundbreaking because it provided a systematic way to study and reference the night sky, laying the foundation for future astronomical observations and mapping. Hipparchus is also credited with the discovery of the precession of the equinoxes, a phenomenon where the positions of stars shift gradually over time due to the wobbling motion of Earth's axis.

The importance of Hipparchus' star chart to astronomy is profound. It represented a monumental step forward in the cataloguing and understanding of celestial objects. By establishing a baseline for the positions of stars, Hipparchus enabled future astronomers to track changes and movements in the night sky, contributing to the development of more accurate astronomical theories and models.

Additionally, Hipparchus' work influenced later astronomers, including Claudius Ptolemy, whose own star catalogue in the Almagest built upon Hipparchus' foundation. The legacy of Hipparchus' star chart endured through the centuries, all the way and including Charles Messier's comprehensive catalogue, shaping the methods and practices of astronomical observation and charting.

In 1054 CE, Chinese astronomers recorded a supernova, an event that significantly impacted the field of astronomy. This supernova, now known as SN 1054, was visible in daylight for 23 days and in the night sky for almost two years. The remnants of this supernova are now observed as the Crab Nebula (Messier 1), located in the constellation Taurus. This represents one of the earliest detailed observations of a supernova explosion. Chinese astronomers meticulously documented the event, noting its brightness and duration, which provided valuable historical records for future astronomers.

The importance of this event to astronomy lies in its contributions to our understanding of stellar life cycles. The detailed observations made by Chinese astronomers offered early evidence of the explosive deaths of massive stars, leading to the formation of nebulae and other celestial phenomena. Additionally, the Crab Nebula became a crucial object of study for modern astronomers, helping to advance knowledge in areas such as neutron stars, pulsars, and the mechanics of supernova explosions.

The heliocentric model was re-proposed by Nicolaus Copernicus in 1543 with the publication of his seminal work "De revolutionibus orbium coelestium" (On the Revolutions of the Celestial Spheres). This model posited that the Sun, rather than the Earth, is at the center of the universe, with planets, including Earth, orbiting around it.

The heliocentric model's re-proposition marks a significant point in the timeline of astronomy, as it challenged the long-standing geocentric model endorsed by Ptolemy and the Church, which placed Earth at the universe's center. Although the idea of a Sun-centered universe had been suggested by ancient Greek astronomer Aristarchus of Samos circa 250 BCE, Copernicus' work provided a more comprehensive and mathematically robust framework.

This seemingly-trivial publication (to our enlightened minds, anyway) fundamentally altered our understanding of the universe's structure and was the catalyst that initiated the Scientific Revolution. By shifting the perspective from an Earth-centered to a Sun-centered system, Copernicus' model paved the way for further advancements by astronomers such as Johannes Kepler and Galileo Galilei. Kepler's laws of planetary motion and Galileo's telescopic observations provided further evidence supporting the heliocentric model, ultimately leading to its widespread acceptance.

The formulation of the three laws of planetary motion by Johannes Kepler took place between 1609 and 1619, marking a pivotal period in the history of astronomy. These laws described the motion of planets around the Sun with unprecedented accuracy, transforming our understanding of the solar system. Kepler was a German mathematician, astronomer, and astrologer, who formulated his laws through a growing understanding of calculus and precise observations made prior.

The first law states that planets move in elliptical orbits with the Sun at one of the two foci. This was a significant departure from the previously accepted circular orbits posited by earlier models. The second asserts that a line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time. This law implies that planets move faster when they are closer to the Sun and slower when they are farther from it, departing from the idea of a constant speed of movement. The third law establishes that the square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit. This relationship provided a precise mathematical description of the relationship between a planet's distance from the Sun and the time it takes to complete an orbit.

These laws were formulated through meticulous analysis of the astronomical observations made by Kepler's mentor, Tycho Brahe, whose precise measurements of planetary positions provided the empirical data needed for Kepler's work. The importance of Kepler's laws to astronomy cannot be overstated. They provided strong support for the heliocentric model proposed by Copernicus, which placed the Sun at the center of the solar system rather than the Earth.

The discovery of Neptune occurred in 1846 and was notable not only because it expanded our knowledge of the solar system but also because it was the first planet discovered through mathematical prediction rather than direct observation. The French mathematician Urbain Le Verrier and the British mathematician John Couch Adams independently calculated the position of Neptune based on irregularities in the orbit of Uranus. These irregularities suggested the gravitational influence of an unknown planet. The planet was confirmed by observation at the Berlin Observatory very close to the position predicted by Le Verrier.

The importance of Neptune's discovery to astronomy was profound. First, it demonstrated the power of mathematical prediction in astronomy, setting a precedent for future discoveries. Second, it confirmed the existence of another major planet in the solar system, thus refining our understanding of its structure. Neptune's discovery also led to further investigations into the outer solar system, eventually contributing to the discovery of Pluto and other trans-Neptunian objects.

How can we talk about astronomy without mentioning Einstein? The Theory of General Relativity (GR) was first published by Albert Einstein in 1915. This groundbreaking theory is a cornerstone in the timeline of physics and astronomy, fundamentally transforming our understanding of gravity, first quantified by Isaac Newton in 1687. Einstein's theory extended his Special Theory of Relativity, which he had previously published in 1905, to include acceleration and gravitation, thus providing a new framework for understanding the gravitational interaction.

GR introduced the world to the idea that gravity is not a force between masses but rather a curvature of spacetime caused by mass and energy. This new perspective allowed for more accurate predictions of gravitational phenomena and explained anomalies that Newtonian physics could not, such as the precession of Mercury's orbit. It predicted phenomena such as gravitational waves, black holes, and the bending of light by gravity (gravitational lensing). These predictions have been confirmed through various observations and experiments, solidifying the theory's validity.

The Big Bang Theory, which describes the origin and evolution of the universe, was first developed in the late 1940s. The most significant contributions came from physicists George Gamow, Ralph Alpher, and Robert Herman. This theory posits that the universe began as an extremely hot and dense singularity (point of energy/mass) approximately 13.8 billion years ago. It has been expanding ever since.

The development of the Big Bang Theory represented a profound shift in our understanding of the cosmos. Prior to this, the prevailing belief was the steady state theory, which suggested that the universe had no beginning or end and was in a constant state of creation. The Big Bang Theory, however, proposed that the universe had a specific inception point and has been evolving, expanding, and cooling over time.

One of the pivotal events in the development of the Big Bang Theory was the prediction and subsequent discovery of the cosmic microwave background radiation (CMB). In 1948, Gamow, along with his colleagues Alpher and Herman, predicted the existence of this residual radiation from the early universe. This prediction was confirmed in 1965 by Arno Penzias and Robert Wilson, who detected the CMB, providing strong empirical support for the Big Bang Theory.

The first confirmed discovery of exoplanets was announced in 1992, marking a significant milestone in the timeline of astronomy. These exoplanets were found orbiting a pulsar, PSR B1257+12, by astronomers Aleksander Wolszczan and Dale Frail. This discovery was groundbreaking because it provided the first concrete evidence of planets existing outside our solar system, expanding our understanding of the universe and the potential for other habitable worlds.

Exoplanets, meaning extrasolar planets, are planets that orbit stars other than our Sun. The detection of these planets around a pulsar - a highly magnetized, rotating neutron star - was unexpected. The extreme conditions around pulsars were not considered conducive to planet formation. This finding challenged previous assumptions and prompted further exploration into the diversity and formation of planetary systems.

This event opened the floodgates for further exoplanet research, leading to the discovery of thousands of exoplanets in subsequent years. Many of the ones discovered have been found in more conventional star systems. This discovery has profound implications for the search for extraterrestrial life, the potential for exosolar travel, the study of planetary formation and evolution, and our understanding of the cosmos.

The first image of a black hole was captured in April 2019 by the Event Horizon Telescope (EHT) collaboration. The EHT is a global network of radio telescopes working together to function as a single Earth-sized telescope, achieving the necessary resolution to observe the event horizon of a black hole. The image revealed a bright ring formed by light bending in the intense gravity around the black hole, with a dark central region known as the shadow, corresponding to the black hole itself. This achievement not only provided the first direct visual evidence of a black hole but also opened new avenues for studying these fascinating objects.

This historic milestone in the timeline of astronomy holds significant importance as it provided visual confirmation of the existence of black holes. Prior to this, they had only been predicted by Albert Einstein's theory of general relativity, a treatise published over a century earlier. The black hole in question is located in the center of the galaxy M87, a massive galaxy in the Virgo cluster, approximately 55 million light-years away from Earth.