The Origins of Astronomy: A Journey Through Time and Space

Astronomy encompasses the study of the Universe as a whole, including the various celestial bodies that comprise it: stars of different types along with their planets and satellites, which, together with interstellar matter, form galaxies. These galaxies, when grouped, create clusters and superclusters. Astronomers describe celestial bodies, investigate their composition, and analyze the relationships they maintain with one another as well as their evolution over time.

Astronomy is divided into classical astronomy and astrophysics. The branches of classical astronomy include positional astronomy—also known as astrometry or spherical astronomy—which focuses on locating celestial bodies through various coordinate systems in space and time. Additionally, celestial mechanics studies the movements of planets, satellites, and other celestial objects, relying fundamentally on Newton's law of universal gravitation.

Astrophysics, on the other hand, applies theories and techniques from physics to the study of celestial bodies, primarily utilizing methods developed since the early 20th century, such as photometry, spectroscopy, and the analysis of radio waves emitted by celestial objects, known as radio astronomy.

Within astrophysics, several subfields can be identified: stellar physics, which examines the structure and composition of stars; cosmogony, which deals with the origin and evolution of all celestial bodies; and cosmology, which studies the structure and evolution of the Universe as a whole.

Historical Background

As one of the oldest sciences, astronomy has significantly contributed to the development of various other disciplines, including mathematics, physics, and geography. Ancient cultures such as the Babylonian, Chinese, Egyptian, Greek, Indian, and Maya possessed rudimentary astronomical knowledge, primarily based on naked-eye observations, which were often applied for practical or mythological-religious purposes. Astronomical theories in antiquity were heavily influenced by Aristotle's authority (4th century B.C.) and the belief in the Earth's immobility. Significant observational work from this era is attributed to the Greek astronomer Hipparchus (late 2nd century B.C.), whose findings have survived to this day in the Arabic version of his work known as the "Almagest" (9th century), thanks to Ptolemy (late 2nd century A.D.). Through naked-eye observations complemented by rudimentary instruments (like astrolabes and cross-staffs), early astronomers established the Earth's sphericity, connected lunar movements with tides, created the first star catalogs, and determined the parallax of certain celestial bodies. Later contributions from astronomers such as Nicolaus Copernicus, Tycho Brahe, and Johannes Kepler laid the scientific foundations of this discipline: the heliocentric theory, the creation of extensive astronomical tables and catalogs, the establishment of permanent astronomical observatories, and the formulation of the laws of planetary motion (Kepler's laws).

The Birth of the Universe

As we delve deeper into the origins of the cosmos, the phenomena and processes become increasingly extraordinary, with numbers that are nearly incomprehensible.

Advancements in particle physics have allowed scientists to trace back to a fraction of a second after the initial explosion. At that moment, the entire Universe was compressed to a size equivalent to an atomic nucleus; everything existed within a single point, devoid of volume. This state is referred to in physics as a singularity; within it, neither space nor time could exist. Thus, the onset of expansion marked the creation of the Universe.

The singularity described by Friedman models is as close as science has come to understanding the act of creation. If we adhere strictly to this concept, we can conclude that not only did space-time begin to exist at the singularity, but so did all the matter in the Universe.

Consequently, the singularity represents a temporal boundary for everything. Thus, the question of what existed before the Big Bang becomes meaningless; there was no 'before' the Big Bang because time itself did not exist. Similarly, the inquiry into what caused the Big Bang loses relevance, as causation implies a temporal order (a cause always precedes an effect) that did not exist until the moment of expansion's inception.

These considerations illustrate that the event of creation is physically far more profound within the framework of relativity than in the biblical account, which posits that matter was created in a pre-existing void.

From ancient times, various cultures have gazed at the skies, striving to unravel the mysteries posed by the stars. Explanations for celestial phenomena have proliferated from Prehistory through Classical Antiquity to the present day. While early theories were rooted in myths and fanciful legends, contemporary understandings are grounded in the results obtained through modern scientific fields such as physics, astrophysics, and cosmology.