Why the Sun Rises in the East and Sets in the West, While Other Stars Appear Fixed
Since ancient times, the Earth's rotation has fascinated humanity. The Sun's daily journey across the sky has been woven into our languages and cultures, with the east being the direction in which the Sun is said to rise, and the west being where it sets each day. This practice has been adhered to since the Earth's rotation was first realized, approximately 400 years ago, based on the heliocentric model proposed by Copernicus and later supported by Kepler, Galileo, and Newton.
The Role of Earth's Rotation in the Sun's Apparent Motion
The Earth completes one full rotation on its axis from west to east, taking about 24 hours to do so. This rotation is what gives us the illusion of the Sun rising in the east and setting in the west. The Sun, however, is not actually moving; it is the Earth's rotation that makes it appear so. This concept has been a cornerstone in astronomy and has helped humanity understand the movement of celestial bodies more accurately.
An interesting phenomenon experienced by many people is the double sunset. This occurs during flights where the plane is moving at a high speed in a westward direction, opposite to the Earth's rotation. As a result, the Sun appears to set twice within the flight. A vivid example of this was observed in 1976 while the author was traveling from London to Montreal. This directly illustrates the influence of the Earth's rotation on the apparent motion of celestial bodies.
Stars in the Night Sky
The behavior of stars in the night sky is entirely different from that of the Sun. While the Sun appears to move from east to west due to the Earth's rotation, the majority of the stars apparently move in a similar manner. However, they do so at a slightly faster rate because the Earth's orbital motion around the Sun shifts the line of sight to different stars. Essentially, the Earth's orbital motion shifts the Earth-Sun direction eastward, completing one revolution per year.
Another fascinating observation is the movement of stars. Stars located near the celestial equator rise in the east and set in the west. Stars that are farther from the equator rise and set at different points on the horizon, depending on their distance from it. Stars close to the celestial poles, as seen from a specific latitude, do not rise or set but instead move in circles in the sky due to the Earth's rotation.
The Formation of the Solar System
The Earth's rotation and its position in the solar system played a crucial role in the formation of the Sun and the planets. About 4.6 billion years ago, from a cloud of gas and dust called the solar nebula, the Sun formed at the center, surrounded by a thin disk of matter that eventually resulted in the formation of the planets.
A shock wave from a nearby supernova explosion likely initiated the collapse of the solar nebula, leading to the creation of our solar system. Our heliocentric model, a concept that has been around for about 400 years, provides a more accurate understanding of the universe's structure. In contrast to the old geocentric model, the heliocentric model posits that the Earth is not the center of the universe, and the human race is not the center of everything on Earth.
Today, the heliocentric model remains the most accepted model of the universe, despite some people still holding on to the belief that the human being is the "crown of creation." Understanding the true nature of our place in the universe is crucial for advancing our scientific knowledge and appreciation of the cosmos.