Most of the so called "Sci-fi blockbuster films" that we normally watch in cinema or streaming platforms are presenting us with an environment where explosions are noisy and bright, fire is everywhere, people wander around with no issues, and spaceships can sail around a planet like a boat sails around an island. This text would present you (the reader) some of the basics concepts to understand what space is, what it is made of and how far from the popular concept of "nothingness" it is.
Most of the so called “Sci-fi blockbuster films” that we normally watch in cinema or streaming platforms are presenting us with an environment where explosions are noisy and bright, fire is everywhere, people wander around with no issues, and spaceships can sail around a planet like a boat sails around an island.
This text would present you (the reader) some of the basics concepts to understand what space is, what it is made of and how far from the popular concept of “nothingness” it is.
Space is a literally a never-ending topic, an open research and discussion field that allows for endless papers and dialogues, but there are few fundamental terms that you as reader should know about in order to be able to fully grasp the meaning of this text.
What is Space?
Space has dimensional meaning; we express our daily lives in terms of space: in length, area or volume, space is in itself the semantic container of the three dimensions that shape our world.
When astronomers started to look outside our little round habitat called Earth, they noticed that there were vast distances between the observed celestial objects; in any direction there was one thing in abundance above everything else, space – enormous and unquantifiable amounts of it. Maybe this was the reason why they called this region outside our atmosphere “outer space,” which with time was simplified to “space.”
But where does the space start? For years this question had not a single answer and depending on the place on Earth where you were standing or even the scientist that you asked, the results would be different.
The main issue was related to the nation’s sovereignty of airspace. From 1957 when the first satellite Sputnik was launched by the Soviet Union, until 1967 when the American Gemini program started, only 10 years had passed, but the world went from zero objects in space to dozens of them. These were Cold War times, when the risk of weaponizing space and being destroyed by another superpower was the only thought. All this led to the creation of the first “Outer Space Treaty” in October of 1967 signed by the Soviet Union, USA and United Kingdom. In a nutshell, this implies that space should be used only for peaceful purposes and freely by any nation; you can browse it online for more details.
By 2021, a total of 111 countries have signed the Outer Space treaty and four more have been created, all of them under the auspices of the United Nations.
Already introduced above, the issue for sovereignty of airspace was now more than ever, important to define. Where does a nation’s airspace finish and space start? This is nowadays still a very debatable question and there is not a full consensus among countries, so we can imagine the confusion and chaos surrounding this question back in the 1960’s.
At this point a brilliant Hungarian-born mathematician, physicist and aerospace engineer stepped in to try to bring some clarity to this issue. Theodore Von Karman was famous for his work with wind tunnels and supersonic flights, aircraft structures and several other aeronautical disciplines.
He was the first one to calculate the altitude where the force that keep airplanes in the air – the “lift,” which is dependent on the air density, air speed and wing surface – is no longer big enough to keep the vehicle flying. Even with an infinite wing, the aircraft would have to fly so fast to stay afloat that it would reach a velocity at which the gravitational pull exerted by Earth is “balanced” by the centrifugal force keeping the aircraft in a permanent orbit around Earth –what is called “orbital velocity.” Thus the aircraft can now be called Spacecraft.
Von Karman calculated this altitude to be at 100Km from the Earth’s surface, and it has been widely accepted (but not fully), including by the United Nations, who it uses this term for most of their treaties; although it leaves room for different limits, Space Law is a very complex topic to address.
But for you reader, we can consider that “space” will start at an imaginary line 100 Km above the Earth’s surface called “Karman Line.” So if you are smart and lucky enough to get a job in a space agency and join one of their programs to visit the International Space Station, or you are rich enough to be able to pay hundreds of thousands or even millions of dollars for a ticket as a space tourist, remember that as soon as you cross the Von Karman Line you will automatically become an Astronaut (cosmonaut if you are in Russia), not before, even if you can even orbit and float, only above 100km can be called Space. And also, remember to book a return ticket.
Floating in Space
Although gravity drops by the square with the distance away from Earth, astronauts in space don’t float because they are very high, they are actually in a constant “fall.”
You might wonder, “why do astronauts float in the ISS?” Well, the reason is not because they are orbiting at 400 km over the surface but rather because they are travelling at 28,000 km/h. Yes, if you want to float you have to fly faster, orbital velocity, remember? The effect of floating is thanks to the centrifugal force generated when flying at such great speeds; this force is what makes you get out of the road in a tight curve, or how to avoid the water to be spilt when spinning a full glass in circles. The further we are from Earth the slower we need to orbit to obtain this effect.
We also say that astronauts are in a perpetual fall, because if you could fall from a high altitude towards Earth and remove all the air, you would actually feel that you are floating; this effect can be experienced when we ride a roller coaster on a quick down path or while we are flying on an airplane during heavy turbulence that causes the plane to fall down like a stone for a few feet (brace yourself if it is more than that), that sudden down motion creates a floating sensation on us most of the time, one not very welcomed by our stomachs. This “floating effect” is widely used by space agencies and their ZERO G airplanes, which creates zero gravity simulations for short periods of time (under one minute).
By the way, just in case you wonder, it is said that every astronaut vomits in space.
What if I go further and further away from earth, would I float without being in motion? Unfortunately, no. Indeed, if you keep distancing from Earth the planet will eventually stop exerting a “pull” on your body; at that moment you could say that you have left the Hill Sphere which is an spherical aera where the Influence of Earth gravitational pull is small enough to be neglected, with respect to other celestial bodies, in the case of our solar system, with respect to the Sun. Every celestial body has one: Mars, Venus, Jupiter, Sun, The Moon, even asteroids have this sphere.
As you might have realized by now, in space everything is about “balance” and of course when there are two celestial bodies pulling each other there must be some points where the forces of both cancel out. For Earth and Sun system, these points are called Lagrange points and they represent points were the gravitational forces of the two large bodies and the centrifugal force balance each other.
We cannot stay static
Ok, you have made to the Lagrange points and passed them, Now I might be free of any influence and float statically, right? I am afraid it’s a no again; as soon as you are free of the Earth’s influence you would be “captured” by another bigger influence, in the case of our solar system, the sun. This means that you still have to move to avoid falling into the sun or any other body around you.
There aren’t straight lines
Because of the above we cannot travel in straight lines as we always see in our favourite Sci-fi movies, not with our current technology at least. There will be always a planet, an asteroid or any other body that will try to attract your body towards it, pretty much like the myth of the Sea Sirens and the sailors, where beautiful feminine sea creatures were singing and hypnotizing to attract them and take them to the bottom of the seas to never be seen again. A celestial body won’t sing to you, but will drag you to the bottom of its “sea” without a doubt.
Other problems in Space.
Extreme temperatures, radiation, microgravity, vacuum, micrometeorites, space junk, alien microorganisms, and isolation are some of the issues that one has to solve to be able to put a human into space, and for which we humans have not yet found permanent solutions – only temporary ones that allow us to explore just the outer side of our home door for very short periods of time.
I hope you have now a better idea of what is “up there,” and all the things that have yet to be solved. Topics like humans in space, or Space Junk, or The Future of Space Business are some of the possible articles that might come in the future, so stay tuned and posted with the website.
Patxi Daniel Rodríguez Acero
Aircraft Engineering&Aerospace MA.