Introduction to Astronomy

Since a long time ago, humans have observed the stars to guide themselves on the surface of the planet. Location is the first step in studying Geography since this science describes and explains space. In this discipline, locating is equivalent to dating in History. 

Thanks to the study of the stars, the ancient "geographers" began to develop techniques and knowledge that led to the construction of Cartography and, within Cartography, concepts such as geographic coordinates, latitude and longitude, meridians, and parallels. Even today, modern satellite positioning systems base themselves on this knowledge.

Universe: origins and structure

The Universe is the collection of everything that exists, or that we can say exists, based on the scientific knowledge currently at our disposal. Within this whole are ordinary matter, dark matter, and dark energy, which are the main building blocks of the cosmos.

Dark matter and dark energy are unknown and observable indirectly. Ordinary matter is about 5% of the volume of the universe, the other 95% is composed of unknown components, as well as dark matter and dark energy.

Almost all ordinary matter is concentrated in the stars. Stars are large clouds of gas and dust fused in their core, generating the energy that makes them shine. They are grouped in galaxies, which can have from 10 million to 1 trillion stars each. 

Solar System 

Composed of a collection of stars, planets, natural satellites, comets, asteroids, dwarf planets, and the Sun, the Solar System represents 99.86% of its mass. Besides having this disproportionate share, it is around this star that the other bodies orbit. Therefore, the very notion of the Solar System is linked to the heliocentric model, developed by Nicolaus Copernicus, Galileo Galilei, and Johannes Kepler.

Nowadays, science recognizes eight planets in the Solar System. All of them have in common that they are large enough to have acquired a round shape due to their gravity, but not to the point of developing the process of nuclear fusion, which causes stars to have their light.

We can divide the planets of the Solar System into two groups. The first is the telluric planets, with solid surfaces and much smaller sizes than the others: Earth, Mercury, Venus, and Mars. The second group is the jovian ones, gaseous and of much larger proportions: Jupiter, Saturn, Uranus, and Neptune. 

The telluric planets are closer to the Sun, so they are called inner planets, and the jovian planets are farther away and are known as outer planets. Between these two groups is a belt of asteroids, which are much smaller bodies in orbit around the Sun.

Meteoroids are fragments of solid matter, smaller than an asteroid and bigger than an atom and moving through interplanetary space. When one of these fragments enters the Earth's atmosphere, the friction with the atmospheric gases causes them to burn up and produce a glowing cylinder, known as a shooting star. This phenomenon is called a meteor. However, if this body is not burned off during the fall and reaches the surface, it is called a meteorite.

To finish this description of the Solar System, we need to talk about comets, which are smaller bodies made of ice and dust. They have very eccentric orbits. When they are closer to the Sun, their ice structure is affected by solar radiation and winds, causing the formation of a tail.

The Earth and its movements

The movement of rotation is the one that the Earth makes around its axis, bringing several consequences to our daily lives. To begin with, we will highlight the possibility of creating a localization system based on directions and geographical coordinates.

The directions north, south, east, and west are directly related to this movement. The first two refer to the poles, which are the ends of the axis formed by the Earth's motion around itself. The east direction coincides with the course of rotation, and the west direction is contrary to it.

These four fundamental directions are called cardinal points, and among them are the following collateral points: northwest (NW), northeast (NE), southeast (SE), and southwest (SW). There are also sub-lateral points, which are between the first two groups. Those directions are all represented in the wind roses.

The directions represented in the compass rose are used primarily for orientation.

The Earth's magnetic field

Formed by the movement of rotation and the consequent movement of the planet's outer core, the Earth's magnetic field is metallic and in a liquid state. This field presents an oscillation, a constant variation, resulting in magnetic declination. 

From orientation to localization

The movement of rotation allows us to use orientation techniques, and through them, we can follow directions on the earth's surface from the point where we are. Thus, we will see that the combination of north-south and east-west directions helps locate any point on the surface.

Coordinates are the value of latitude and longitude, combined, based on the parallels and meridians, respectively, that define a point as they intersect.

The meridians and the parallels serve as a reference for defining latitudes and longitudes. Latitude and longitude are measured in degrees.

The intersection of latitude and longitude establishes the location of a point on the Earth's surface. Geographic coordinates are used in this way.

Translation and its consequences

The translation motion happens when the Earth moves around the Sun as it follows its elliptical orbit, in which it approaches and slightly departs from the Sun. The point of greatest proximity is the perihelion, and the point of greatest distance is the aphelion.

The Earth makes its journey approximately every 365 days, 6 hours, 9 minutes, and 9 seconds. One of the results of this movement is the definition of the terrestrial year.

The solstices are the times when the sun's rays fall perpendicularly on one of the tropics. The sun passes through the zenith of all the points that form each of the two notable parallels.  

There are two types of solstices: The summer solstice, which marks the beginning of summer. And the winter solstice, indicating the beginning of winter.