In addition to the pandemic, the climate crisis and the situation in Afghanistan, this year has been characterized by the amount of space travel made by billionaires. On July 11, Richard Branson, owner of Virgin Group, managed to beat Jeff Bezos in the race to become the first billionaire to travel into space in a ship manufactured by its own company. Although Bezos was not the first, he also managed to travel to space aboard his New Shepard ship on July 20, Colombia's independence day.

Space is fashionable, or maybe it always has been and this is only the moment when we have had more and better technology to explore it. It can be said that the stars have always been the object of observation and study for the human being. Civilizations such as the Aztec, Chinese, Hindu, Greek or Mesopotamian recorded numerous celestial events and they made measurements of the stars and their orbits.

Representation of the constellations "Astronomicum caesareum". Photo: Pedro Apiano (Royal Institute and Observatory of the Navy)

Since ancient times, there were already students of the celestial bodies or what we know today as astronomers. Some of those first researchers who became interested in the cosmos and set their sights on the sky were Hipparchus of Nicea and Claudius Ptolemy. Hipparchus of Nicaea was a Greek astronomer who stood out mainly for creating the first catalog of stars. For his part, Claudius Ptolemy was also a Greek astronomer who stood out for his model of the geocentric universe.

This model affirmed that the Earth remains immobile in space and occupies the center of the universe, and that the Sun, the Moon, the planets and the stars revolve around it. It is worth mentioning that in the XNUMXth century, the Ptolemy model was replaced by the heliocentric theory of Copernicus.

Although human curiosity for space began in ancient times, it did not diminish over time. Centuries after those first onlookers, the modern astronomy with the studies of Nicolás Copernicus and the subsequent invention of the telescope, which has a controversial origin.

Scene from 'Le voyage dans la Lune'. Photo: Brief Story of the Cinema (Flickr)

Space has not only been an object of interest to scientists, it has also given rise to imagination and fantasy. In 1634, around the time of Galileo Galilei, the first science fiction novel was published, Dream. The text was written by Johannes Kepler and tells of a hypothetical journey to the moon. Centuries later, the famous French writer Jules Verne wrote his fictional novel 'From the Earth to the Moon', a book that shows a group of men traveling to the Moon using a large cannon. In 1902, 'The trip to the Moon' (Le voyage dans la Lune), the silent film by French director George Mélliès.

As you can see, the cosmos has been the protagonist of numerous works of art and since ancient times human beings have already shown curiosity about it. That is why it is no coincidence that this year all the records de satellite launches, since 1.400 of these devices have already started to circle the planet so far in 2021.

The trend is that in the coming years there will be more launches and space missions to the Moon and Mars. The investigation of the cosmos and its conquest do not stop, but how much do we know about astronomy and what would be the most interesting concepts to consider in a world that is heading towards space exploration?

Some of the most popular are shown in this article.

1. The Kármán line

Many have the dream of traveling to space since childhood, but there are really few who manage to realize that dream, at least at this time. As already mentioned, billionaires Bezos and Branson managed to fulfill that dream last July. Despite this, the question remains as to whether they really reached space or whether they did not exceed the limit that exists to reach it. This limit is known as the Kármán line, an imaginary line that is located above the earth's surface and that establishes the boundary between the Earth and outer space.

Originally, Theodore Von Kármán, a Hungarian-American engineer and physicist, considered that at a height of 80 kilometers it was not possible for an airplane to be able to sustain itself in the air and, indeed, it is impossible for a normal airplane to climb to that height. For Gregorio Portilla, professor at the National Astronomical Observatory and doctor in theoretical physics in active galaxies, there is a problem with the Kármán line and it is the discussion about its value. Kármán established it at 80 kilometers, but over time the line went up a bit more, to 100 kilometers.

This is the height recognized by the International Aeronautical Federation (FAI) and for that reason it is argued that the British Richard Branson did not travel into space (at least for the FAI), because he only reached a height of 86 kilometers. However, the United States has its own limit, which is considered from 80 kilometers in height, since at that point it goes from a deep blue color of the sky to a black typical of space. Additionally, at that height it is already possible to float in weightlessness and observe the curvature of the Earth.

For Professor Portilla, the importance of the limit at which the Kármán line is located is relative, because it is very difficult to establish where the Earth's atmosphere ends and where space begins exactly. «For the purposes of records and statistics it is preferred to have a reference point. That is the role that the Kármán line plays »said Portilla. The scientist also assured that the choice of 100 kilometers, which many have adapted, is a round number and easy to remember «In an environment where 20 km above or 20 km below give practically the same thing».

2. and 3. Astronomy vs. astrology

For many people the difference between these 2 subjects is not clear, since they have similar names and in the long run both are associated with the stars. Despite this, both disciplines are quite different. Colleagues from Universia they affirm without qualms that astronomy is a science and astrology is a pseudoscientific belief, that is, a belief or practice that is incompatible with the scientific method.

According to the book '100 Basics of Astronomy', carried out by members of the Spanish Society of Astronomy and the National Institute of Aerospace Technology of that country, astronomy is in charge of studying the positions, distances, movements, structure and evolution of the stars based on the information contained in electromagnetic radiation or the particles that reach the observer.

In simpler terms, Astronomy studies celestial bodies (stars, natural satellites like the Moon, planets, etc.) by means of light particles (photons), X-rays or other frequencies. Most of the information used in this science is collected thanks to the use of instruments such as telescopes.

Night view of the Milky Way from the Paranal platform, Chile. Photo: HH Heyer (Wikimedia Commons)

According to the Spanish book, at first astronomy and astrology were almost indistinguishable from each other, but the content and procedures of astrology have stopped over time. Astrology studies the relative positions and movements of the real celestial bodies and how they influence people and the world; part of the unproven assumption that some stars influence our reality.

Astrology, however, has become quite popular, especially on Twitter. For the team of scientists who created the book '100 Basics of Astronomy', astrology has failed in its attempt to predict the future and "Its relative success is justified, because its descriptions are so general and ambiguous that they apply to almost anyone".

What the Royal Academy says

Astronomy: 1. f. Science which deals with the stars, their movement and the laws that govern it.

Astrology:. F. Studio of the position and movement of the stars as a means of predicting future events and knowing the character of people.

Regardless of the position cientIn terms of astrology, these beliefs have been present in many cultures throughout history, and around them are generated open spaces for constructive debate.

4. And what is cosmology?

Unlike the previous concepts, cosmology is not usually on people's radar and it may not arouse as much interest as astrology, but the truth is that it is a very valuable branch of knowledge. In simple terms, cosmology is a branch of physics that studies the universe as a whole and in particular its origin and evolution. Cosmology is so important that it is the branch in charge of studying the first moments of the existence of the cosmos. It may sound very nerdy, but it is actually exciting.

5. Light year

In 1977 the first film of the original Star Wars trilogy was released. Many fans of the series will remember that iconic scene where the Millennium Falcon, Han Solo's ship, took a leap at the speed of light in hyperspace to escape the fleet of the Galactic Empire. Although this is part of the fiction, several master's students in physics at the University of Leicester, in England, they took the trouble to study this fact and they concluded that traveling aboard the ship at that speed would be a little different from how George Lucas showed it.

Photo: Pxfuel

The hyperdrive or hyperspace concepts that appeared in Star Wars were used in the setting of a sci-fi universe, but may find a good resemblance to the light-year concept. A light year is a unit of distance used in astronomy that is equivalent to the distance that light travels in one year (remember that light travels at almost 300.000 kilometers per second). A light year is equivalent to almost 9 trillion (millions of millions) and a half kilometers (9.460.730.472.580 kilometers, more exactly), which is established by the International Astronomical Union. To give you an idea, the distance between the Sun and the Earth is about 150 million kilometers, so it would take 'only' 8 and a half minutes to travel from our planet to the Sun at the speed of light. Amazing!

Main photo: NASA