From time to time, NASA reminds us with some anecdote or study that things are never how they seem or, failing that, that can always be questionable or have more than one answer. Recently they gave us such a simple explanation about our inability to find extraterrestrial signs that scared. They also clarified why we hadn’t returned to the moon before. The latest: remember that, technically, no human has ever left the earth’s atmosphere. And yes, I don’t even want when we went to the moon.
A technically true provocation. To say that no astronaut in history has ever left the earth’s atmosphere may sound to a joke or little less than a conspiracy theory, but, from a scientific perspective and following what atmospheric models say, it is more than a correct statement.
To place ourselves in perspective and following this line of explanation, even iconic figures such as Yuri Gagarin or Neil Armstrong, or contemporary space travelers such as William Shatner, have remained, in physical terms, within the most extreme (although diffuse) limits of the atmosphere of the earth. The key lies in how the end of that atmosphere is defined: a more complex and expansive issue of what is commonly believed.
The atmosphere does not end where we imagine. All this reasoned Doug Rowland, an expert in NASA’s heliophysics. Contrary to the popular idea that the atmosphere ends in a finite layer that dissipates before reaching the terrestrial orbit, the reality is that the atmosphere does not have a clearly defined “roof”. On the contrary, it becomes progressively more dim, but continues to spread.
As Rowland said, even hundreds of kilometers on the surface, where the International Space Station (EEI) orbits, there is still a sufficient air density to gradually stop the station. In fact, if it were not periodically driven with rockets, the EEI would end up falling by atmospheric drag.
La Frontera Artificial: Kármán. For practical reasons (such as spatial treaties or legal definitions) an international convention has been adopted: the karm line, located 100 kilometers above sea level, which marks the point where the space theoretically begins.
This line serves as a technical threshold, since 99,99997% of the terrestrial atmospheric mass is below. That said, and as explained by the space agency itself, this definition is useful for regulations and classifications, not so much to describe with physical precision the real limits of the atmosphere.
The geocorone: atmosphere that reaches the moon. In 2019, a study based on data from the Soho Solar Observatory (NASA/ESA), revealed that the exosphere of the Earth (in particular, a diffuse cloud of hydrogen atoms known as the geocorone) extends to about 629,000 kilometers, that is, beyond the orbit of the moon.
What happens? That on that limit there are still about 0.2 hydrogen atoms per cubic centimeter. That means that, technically, even the Apollo missions that alunizarized in the 60s and 70s did not abandon the earth’s atmosphere. “The moon flies through the Earth’s atmosphere,” said Igor Baliukin, lead author of the study, referring to the unsuspected magnitude of this invisible layer.
The sun also contains us. The thing is even more complicated when both the Earth and the Moon are inside the solar atmosphere. This extends to the edge of the helosphere, the limit beyond which the interstellar space begins. At this point it must be remembered that between the atmosphere of the earth and that of the sun there is no emptiness, but a structure of progressive and overlapping layers that contain particles, energy and electromagnetic dynamics.
Therefore, and seen thus, the concept of “being in space” is less a matter of abrupt border and more a matter of progressive gradient.
So where the space begins? As Rowland explained, the answer depends on the point of view. If you ask where the atmosphere ends in a practical sense, probably about 400 kilometers, where air density ceases to have significant effect on objects.
But from a more rigorous scientific perspective, that atmosphere does not disappear: it only dissipates and dilutes to barely measurable extremes, without disappearing at all. Therefore, “exterior space” is not an empty place, but a continuous environment full of particles, fields and subtle structures. In that sense, all space trips made by humans have elapsed within that extended wrapping that is still part of the planet that launched them.
Image | Jasbond007
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