Norman Kretzmann was an influential American philosopher, known for his work in medieval philosophy, particularly in relation to Augustine, Aquinas, and the development of philosophical thought in the tradition of Western metaphysics. He was a professor at the University of Chicago and made significant contributions to the understanding of topics like time, free will, and the nature of God.

Obsolete calendars are systems of timekeeping that have been replaced or fallen out of common usage due to the adoption of more accurate or standardized methods of measuring time. Throughout history, various cultures and societies have developed their own calendars based on astronomical observations, agricultural cycles, or religious events, but many of these systems are no longer used today.

Mortimer J. Adler (1902–2001) was an American philosopher, educator, and author known for his work in the fields of philosophy, education, and the promotion of the Great Books. He was a prominent advocate of liberal education and the idea that reading and discussing classic literature can develop critical thinking and understanding. Adler co-founded the Great Books of the Western World series and was involved with the University of Chicago's Great Books Program.

The Hipparchus star catalog, named after the ancient Greek astronomer Hipparchus, is a significant star catalog that was produced using the data collected by the European Space Agency's Hipparcos satellite, which operated from 1989 to 1993. The catalog was released in 1997 and contains precise measurements of the positions, distances, and motions of stars.

Hero of Alexandria, sometimes referred to as Hero of Alaxandria, was a Greek engineer and inventor who lived during the 1st century AD, likely between about 10 AD and 70 AD. He is often regarded as one of the most important figures in the history of engineering and mechanics. His most notable contributions include a number of inventions and devices that demonstrated the principles of physics and engineering long before the modern era.

The Dendera Zodiac is an ancient Egyptian representation of the night sky that is found on the ceiling of the Hathor temple in Dendera, Egypt. It dates back to the Greco-Roman period, specifically around the 1st century BCE to the 1st century CE. The zodiac is significant because it features twelve zodiac signs, which incorporate elements of both ancient Egyptian and Hellenistic astrology.

The term "Fifth Planet" often refers to a hypothetical planet that could have existed in our solar system between Mars and Jupiter. This concept is primarily related to theories about the early solar system's formation and the dynamics of planetary bodies. In the mid-20th century, astrophysicists proposed that early in the solar system's history, there may have been a fifth terrestrial planet that was disrupted or ejected due to gravitational interactions with the other planets, particularly Jupiter.

Star lore refers to the myths, legends, and stories associated with stars and constellations across different cultures and civilizations throughout history. This body of knowledge often includes interpretations of the stars' movements, their significance in navigation, agriculture, and timing of seasonal events, as well as their roles in various mythologies and religious beliefs. Different cultures have created rich tapestries of stories around the night sky.

The term "lost lands" refers to territories or regions that are believed to have existed in the past but have since disappeared, either through natural disasters, geological changes, or are simply the stuff of legend. Here’s a brief overview of some well-known lost lands: 1. **Atlantis**: Perhaps the most famous lost land, Atlantis is a mythical island mentioned by Plato in his dialogues. It supposedly existed around 9,000 years before his time and sank into the ocean.

Theaetetus was an ancient Greek mathematician and philosopher who lived around 417–369 BC. He is most often known for his contributions to geometry and for his work in the field of mathematics, particularly in the study of solid figures and the theory of irrational numbers. Theaetetus is often credited with the mathematical formulation of types of numbers, including the classification of numbers into rational and irrational.

The term "Zodiac" can refer to several concepts, primarily in astrology and astronomy. Here are the key meanings: 1. **Astrological Zodiac**: In astrology, the Zodiac is a circle of twelve 30-degree segments that represent different astrological signs. The twelve signs are Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces. Each sign is associated with specific personality traits, behaviors, and influences.

Apollonius of Perga (circa 262 – circa 190 BCE) was a Greek mathematician and astronomer, known primarily for his work in geometry. He is often referred to as "The Great Geometer" for his significant contributions to the field, particularly in the study of conic sections.

The Delphic Hymns are a pair of ancient Greek hymns that were composed in honor of the god Apollo and were performed at the Delphic Oracle, a prominent religious site in ancient Greece. These hymns are notable for their musical notation, making them some of the earliest examples of written music that have survived to modern times.

Hippocrates of Chios (circa 460–370 BCE) was an ancient Greek mathematician and philosopher known for his contributions to geometry and mathematical science. He is best known for his work on the properties of geometric figures, particularly in the context of Euclidean geometry.

Plato was an ancient Greek philosopher who lived from approximately 427 to 347 BCE. He is one of the most influential figures in Western philosophy and is best known for his works that explored various topics including ethics, politics, metaphysics, epistemology, and aesthetics. Plato was a student of Socrates and the teacher of Aristotle, forming a foundational trio in Western philosophical thought. His writings are often in the form of dialogues, featuring Socratic questioning and discussion.

Aristotle was an ancient Greek philosopher and scholar who lived from 384 to 322 BCE. He is one of the most influential figures in Western philosophy and has made significant contributions to various fields, including ethics, metaphysics, politics, logic, biology, and aesthetics. Aristotle was a student of Plato and later became a teacher himself, founding his own school known as the Lyceum in Athens.

Chrysippus was an ancient Greek philosopher who lived from approximately 280 to 206 BCE. He is best known as a prominent figure in the Stoic school of philosophy. Chrysippus played a crucial role in developing Stoic thought, particularly in areas such as logic, ethics, and physics. He is often credited with systematizing and expanding the teachings of earlier Stoics, including Zeno of Citium, the founder of Stoicism.

Anaxagoras was an ancient Greek philosopher who lived from around 500 to 428 BCE. He is best known for introducing the concept of "nous," or "mind," as a cosmic principle that organizes and gives order to the universe. Anaxagoras is often regarded as a pre-Socratic philosopher, and he is notable for his contributions to metaphysics and natural philosophy.

Heliodorus of Larissa was a prominent figure in ancient Greek philosophy and rhetoric, specifically associated with the school of Sophists. He is best known for his contributions to the philosophical debates of his time and for his role in the intellectual scene of 4th-century BCE Greece, particularly in the city of Larissa in Thessaly.

Carpus of Antioch was a Christian martyr and saint who is commemorated in the Christian tradition, particularly within the Eastern Orthodox and Roman Catholic Churches. He is often recognized as a martyr who suffered for his faith during the early years of Christianity, around the 2nd or 3rd century. Carpus is generally associated with the city of Antioch, an important early center of Christianity. His life and martyrdom are often linked to broader stories of Christian persecution during that period.