We think we know the real world; it's the one we perceive around us. All we have to do is open our eyes, sharpen our ears and we have a portrait of reality based on our senses. Most of us are perfectly happy with this construction, not knowing or caring that there is a whole lot of reality lurking beyond our senses, invisible and essential.
One of the most extraordinary aspects of science is how it amplifies our perception of reality, opening unexpected windows to the world. The canonical examples are the microscope and the telescope, both from the 17th century and both deeply transformative. Fast genetic sequencing, computer visualizations and fMRIs are some of the tools transforming our current worldview.
On the other hand, science creates its own paradox. The more we learn about the world, the more elusive reality seems to be. Our notion of progress as a linear goal needs to be reevaluated.
Plato, in ancient Greece, anticipated this issue. In his "Allegory of the Cave," part of the Republic, he imagines a group of slaves chained inside a cave since their birth. All they can do is look forward to a wall where images appear. To them, these images are reality, all of it.
What they don't know is that behind them a group of philosophers hold objects against a huge fire, projecting shadows on the wall. What the slaves see, and think of as real, are distortions, two-dimensional projections: a ball is seen as a circle, a pyramid as a triangle, and so forth. Plato's point is that our sensorial perception of the world creates a false notion of reality. We are tricked into constructing a worldview and believing it to be the real thing. When it comes to understanding the nature of reality we are all shortsighted.
History teaches us the same. Before Copernicus, the Earth was the center of the world and everything turned around it. The universe was closed, layered like an onion, and God and his court were on the outside. There was a vertical dimension to existence, and man's mission was to ascend from Earth to eternal bliss in the heavens.
When Newton proposed his theory of gravitation, he realized that the cosmos had to be infinite in extent; otherwise, instabilities would slowly creep in, forcing all the stars to collapse to the center.
Suddenly, reality changed and the world became open and infinite. Man lost his compass, as vertical ascension was no longer the way to go. Darkness was all around us, and no direction was more special than any other. What place for man in this new cosmos? To make things worse, Newton's ideas led to a radical determinism where the future was predictable from the present, at least in principle. In this clockwork universe, what place for free will? Such a bleak, rational outlook led German sociologist Max Weber declare that man had lost his sense of enchantment.
Fortunately, this strict determinism was not to be long-lived. In the beginning of the 20th century, quantum physics put an end to the notion that we can use physics as an oracle. Heisenberg's Uncertainty Principle showed that we can't know a particle's position and velocity (momentum, really) with arbitrary precision. In this case, predicting the future from the present becomes impossible.
Furthermore, quantum physics shows that the nature of reality is truly elusive: we don't see an electron or a photon; we infer their existence indirectly, through detectors. Somehow, in ways which remain unclear, the detector establishes a bridge between the world of the very small and our world of human senses.
In a radical interpretation of quantum physics — the one that we teach in schools and that the overwhelming majority of physicists endorse — we can't even say that the particle exists before we measure it. Reality is defined by how we interact with it.
We have a new way of seeing the world, accepting that there are aspects of reality which are unknown to us. Even more surprising, there are others which are inaccessible. In unexpected ways, modern physics has restored a sense of enchantment which, although not magical, brings back a much-needed sense of wonder.