Some time ago I was having a conversation with a friend who has an advance degree on Evolutionary Biology. She is also a brave defender of animal rights, and we were discussing her difficulties on creating a “world environmental awareness”. Even though, there was a story about a very violent episode where her association fought against some Asiatic fisherman trying to prepare illegal trading of ornamental fish to Europe.

She was telling me that, when you buy an exotic fish, while you are contributing to its extinction, it is very difficult to know the exact way to take care of them in order to guarantee their survival, since an inadequate environment, can produce them a lot of suffer to death. “Fish have complex nervous systems, they react to stimuli the same way as we do, collect information, interact with other entities, hear specific sounds, and observe in detail”. Based on the above and centered on the fact that many people had fish as pets, she was willing at least that her locality approved on Pet shops, a regulation able to control a certain type of curved fish bowls, because the round shape minimized the average oxygen required for the fish to breathe, and secondarily, because it greatly affected the animal's vision, distorting the surroundings completely and generating unnecessary stress all the time, due to the "deformed perception of its reality."

Of course, I do not mean to say having a fish in a round fish bowl is not an abuse, but this last sentence about the “animal's incorrect reality” is very interesting to address, because although it seems men do not live in a twisted fish tank, and beforehand, we know that the fish's vision of reality is different from ours, how can we be totally sure it is less "real"? How do we know, we do not have a wrong perception of "reality"? Regarding the relationship of the human with his certainty, both philosophy and science, have raised this problem and tried to solve what corresponds to human existence: What is real? Are there other realities separate from ours?

Sigmund Freud (the author of psychoanalysis) said it was complex to elucidate what constituted reality.... Physical reality or mental reality? This remarkable psychiatrist exposed the example of a woman suffering from a “delusion of celopathy”, so she was convinced her husband was cheating and acted, consequently, reproaching him for the infidelity. In fact, the guy had never deceived her. The woman acted and behaved, not according to external reality, but according to her psychic reality. In other words, she was convinced that her inner reality was true and authentic.

Other psychiatrists, for example, have seriously proposed to consider sleep periods as a valid alternate reality. The reason is simple: we spend about 20 years of our lives sleeping, and it is illogical to discard so many years, without giving them the appropriate importance in this eternal existential debate.

Different researchers point out, it is only a simulation in which we live manipulated by a supreme being as if we were toys, while some others assure to have proofs that reality is, in fact, a hologram, product of a multifaceted architecture far from human consciousness. It can be an artificial intelligence, just like in the movie The Matrix. Or as the philosopher Rene Descartes said, an 'evil god' that deceives us and prevents us from accessing the next plane of reality.

Taking these examples into consideration, we can guess we do not perceive the completeness of reality (if it “really” exists). In fact, humans do not see that apparent reality, but only a representation of it. Light rays reflecting on objects, entering the eye through the pupil, are focused by the cornea and lens (and also many people need extra help with glasses) to form an inverted image on the retina. The image then translates into nerve impulses, converted into electrical stimuli. Nerve impulses reach the brain divided into information. The shape of the object, the "3-dimensional plane", depth, distance, speed or exact position are not observed at the same time, nor in the same place. The brain associates these data, consults other perceptions, both subjective and emotional, and produces the final images. What we see is not there: it is only in our brain.

From the science’s perspective, although the perception of the fish is different from ours hypothetically, it could generate a whole frame of reference and its own physical laws for all things that can be observed outside “the crystal jail”. For example, an object that moves in a straight line for us, the fish will see it in a curve. However, as I said, models can be created inside the fish tank and in principle, these formulations will be more complicated than ours outside, but their assertions will remain correct and we must admit the vision of the fish is a valid image of reality.

Another case that many people take for granted, for obvious reasons, is the movement of the Earth and the celestial bodies in our solar system. Before Christ, Ptolemy described the movement of the stars around the Earth and also positioned it, as the center of the entire Universe. Then, in the sixteenth century comes De revolutionibus orbium coelestium of Copernicus, telling us in "reality", the planets are moving around the Sun, something we have checked with telescopes and other advanced measurements.

So what is the real model? The one of Ptolemy or the one of Copernicus? Although it seems very evident to say that Copernicus is the winner while the other one is wrong, certainly that is not true. In the same way as our situation with the fish, one can explain the movement of the stars taking into account the Earth or the Sun in a steady state or not. The simplicity of the calculations is relative for each condition, and the frame of reference decided to use.

All of the above can lead us to the disturbing conclusion there is no real certainty about the definition of reality, and nevertheless people believe or try to prove a tangible world, whose properties can be defined and measured in relation to spectators, even to generate laws and natural theories, in fact as far as contemporary physics is concerned, that kind of "classical" perception is already very difficult to sustain.

Let us take the principles of quantum physics, which is a very precise description of nature, but at subatomic scales, and we see that a particle has no definite position, nor a velocity until one of these characteristics is measured by an observer, because just observing them makes the particles behave in one way or another. In that approach, no matter how much information we have about reality, or our ability to measure it, we can never predict it 100% because it is not determined with certainty. These behaviors have been reflected in multiple experiments, such as Young's famous experiment, and direct to the conclusion that humans are no longer merely observers of what we measure, but also actors.

Suddenly, traditionally hard and consistent science questions the paradigm of objectivity and perceptible facts: Can we know reality without interfering with it? And… Can we know it without reality interfering with us?

It seems the presence of a reality’s observer introduces an unavoidable uncertainty: it is impossible to know at the same time all the properties of our reality, because when observing one, we affect the others. In fact our own four-dimensional world is probably only a shadow of some multidimensional universe, according to string theory and worse still, according to M-theory solutions exist that result in an approximate number of 10 ^ 500 universes with an equal number of possible realities, perhaps with different laws and properties we don’t know at all. In that case, where do we end up? What could be the correct way to articulate a true definition, without falling into the ambiguous argument that each person perceives and shapes their own reality?

However, quoting one of the founders of quantum mechanics: "Nothing exists until it is measured." The consequence: we cannot know the Universe absolutely and completely, because in order to do so, we need to know the exact value of magnitudes that, when measured, alter other magnitudes that we also need to know exactly.

According to the allegory of the cave by Plato, chained men consider the shadows of objects as truth, without finding a new reality. "Reality" is what each observer is able to measure, but incompletely. Sadly, perhaps our status is not very different from that of the poor fish trapped in the small bowl.