O QUE É REALIDADE? | Marcelo Gleiser

Do you think you know what reality is? So, it is better to think again! The truth is: reality is very subtle.

It is way more of what we can see through our eyes or listen to with our ears. That's what we are talking about today: the nature of reality and the boundaries of knowledge. Let's go!

What Is Reality? Everything started in ancient Greece when Plato decided to elaborate on one of his ideas about how our senses are misleading, and how our perception of reality gives us an illusion of what is real and has nothing to do with the Truth. Plato was after the Truth, as he wrote on his book "Republic".

In this book, he created the "Allegory of the Cave" (or at least famously know by this name) in which, he counts the following story: imagine a group of slaves chained inside a cave. They are in this situation since they were born (this is just an allegory, guys, a fable) Since their birth, they were in chains, being able only to look to the cave wall in front of them. As when we go to the cinema and see a movie projected on the screen, but we can't look to our back and sides.

So, these slaves also couldn't. They could only look to the front. For them, what they call "reality", their world, was constrained to what they saw in the cave walls.

Because they couldn't look back, they didn't know that there were a big fire and a group of people behind them (which Plato doesn't specify who they were) that projected shadows using objects like statues. They project shadows on the cave walls. creating a false reality -- fake news, guys!

-- to the slaved that were in chains. Why does Plato do that? Preceding "Fake News" in 2500 years, right?

He does that because he wants to differ what we perceive with our senses (our perception of reality) and the world of ideas. And, for Plato, our senses are misleading. In a certain way, he is right.

Why? Because you know very well that, for example, if you are drunk or taking drugs, your perception of reality completely changes. Time passes differently, objects become distorted.

. . your mood changes.

You change! Plato said that our perception of reality is misleading. For example, the slaves thought reality was the projection in the cave walls, but they didn't know this was a major illusion.

So, Plato said "Be careful with your senses. Do not let that your perception of reality is defined by your senses". So, Plato said, if you imagine a circle, the idea of this circle is the only perfect one that exists.

Because it lives in your head. This is the true circle. If you represent this circle on the paper, even if it is a high-resolution printer, the circle represented in "our" reality will never be 100% real.

The circle will be imperfect. Only the idea of the circle, which lives in your head, is real and perfect, thus true. For Plato, if you want to understand reality, you can't look at what is real.

You need to live in the world of ideas. This is Plato's allegory of the cave. That basically said: don't trust your senses.

In a way, Plato is right. We can't look at the world and think that what we see is the "whole story". What we see is part of the story.

Because our perception of reality depends on what we can see, hear, touch, and feel. So, the reality is bigger than what we can perceive, and science's role is to amplify reality; amplify what is real. So, how do we do that?

How does science works? We do that by using instruments and the scientific method to amplify our perception of reality. And we know this, right?

For example, when you think of astronomy history until 1609 all the observations in ancient Greece, Egypt, Babylon, the Middle Age, Rome were made by the bare eye or with instruments as quadrants or sextants. Nothing was amplified using a telescope. Only in 1609, Galileo received a telescope from the Netherlands, improved its magnitude of observation, looked at the skies, and saw a completely different sky than anyone has ever seen for thousands of years.

So, it is not that the sky has changed. What changed was our perception of the sky, because now we had this instrument to amplify reality. I call these spectacular technological inventions "reality amplifiers.

" The telescope was one. The microscope, which was also invented in the 17th century Netherlands, is another reality amplifier because it completely changed our perception of what is life. Suddenly, in a drop of water, small living creatures, that before no one could see with bare eyes, appeared.

So, the questions changed, because now you can ask new questions. Now you have another perception of reality. So, is there a limit to the size of creatures?

Can they become smaller and smaller? When you look at the sky, what are the surprises up there? What are those nebulae that weren't resolved in the 17th-18th century, but now we know they are galaxies?

So, the history of science is the history of how these great technological innovations changed our perception of what is real. Today, when we talk about life, we talk about genetic reproduction, we talk about natural selection, we talk about diseases caused by viruses, bacterias, invisible beings. This is something 150 years ago nobody had a clue about, right?

When we talk about black holes in the middle of galaxies 4-million-solar-mass black holes in the center of our galaxy. . .

When we talk about this, we are also talking about something that no one had a clue 100 years ago. So, these great technological innovations amplify our relationship with reality. I think science, in a certain way, is about this flirt with the unknown.

It is about dedicating a whole life to trying to see beyond what we can perceive. And that's also why the scientific method is based on hypothesis verification. So, you say: I think there is a black hole in the center of our galaxy.

You can guess how much you want it. If you don't have an empiric validation, a validation of your hypothesis through observations very dedicated and strictly precise, y our affirmation doesn't make any sense in science. That's why the 2020 Nobel Prize was awarded to three scientists that proved empirically the existence of a black hole in the center of our galaxy.

A very difficult observation that took 20 years. And it was only possible (and that's important) because we h ave telescopes that allowed these people to prove this observation. This is very, very important.

So, science advances when there is this bond between the scientists' creativity on developing new hypotheses about reality and the creativity of scientists developing these new technological inventions. to create the instruments that allow us to validate or reject all our ideas about reality. This is very important.

The beauty of all of this is that science's language tends to a universalization. It doesn't matter if you are black or white, if you come from China or India, if you come from Rio Grande do Sul or Mato Grosso do Sul. What matters is that you speak the scientific language, that you speak with your colleagues in a form that everybody can understand.

So, on a more fundamental level in practice, things are more complex than this, but this is something for another day To the most fundamental level Science tends to this universal language. So everybody can understand and that can be shared with everybody through scientific communication. You don't need to be a scientist to understand that a black hole exists in the center of our galaxy You need to be a scientist to prove that there is a black hole in the center of our galaxy.

But the information and the validation of this information can be understood by everybody. This is the beauty of science and scientific communication: expanding human reality; expanding our conversation with the unknown. That depends exclusively on our instruments.

Measuring Reality So, two essential things about how we measure reality. First, every measure has a certain precision. A precision limit.

Every instrument measures something––a distance, time interval. We call a "variable. " with a certain precision When you measure your height and you say "I'm 5.

84 feet tall" More or less. You are 5. 84 feet more or less the error of the instrument you used to measure your height.

For example, if the instrument has a division precision of 1 centimeter, you know your height with an error of +/- 0. 5 centimeters. Every precision --it doesn't matter if it is your height or an electron's mass using a highly sophisticated particle accelerator-- every measure has an error.

That means we can't even make an affirmation with 100% certainty. Everything has a margin of error. And the scientist has honestly to say this.

"Look, I know there is a 4-million-solar-mass black hole in the center of the galaxy with an error of 5%. . .

1%. . .

2%. . .

. depending on the precision of this measure" On the other side, we rely on technologies. We can only amplify what is real with the instruments that we possess.

That means we will always have something beyond what we can capture with our reality amplifiers. Beyond our perception of reality. Our instruments completely changed our perception of reality in the last 400 years.

This is the beauty of science. We can make affirmations of things that are billions of light-years distant, or that are viruses, sub-atomic particles that are distant less than a trillionth centimeter. We can make everything with trust.

But we can't make complete affirmations about everything. Because we cannot measure everything. The beauty of knowledge is that it is expanded as we understand more of reality.

But always with the limitation of what is unknown to us. What takes us to the metaphor of "the Island of Knowledge". The Island of Knowledge.

[BOOK IN ENGLISH IN THE DESCRIPTION] In 2014, I wrote a book that was published in many languages, called "The Island of Knowledge". [AMAZON LINK TO ENGLISH VERSION ON THE DESCRIPTION] "The Limits of Science And Our Search for Meaning". What does this Island of Knowledge means?

The idea is based on everything that we discussed until now it is simple Let's imagine that everything we learned about nature, about ourselves fits on an island. As time passes, this island is increasing Because we learn more about the world. Like "every good island" this island is surrounded by the ocean.

The ocean of the unknown, of what we don't know about the world. The island of knowledge is the idea that, when we learn, our knowledge crosses the sea of the unknown. We learn more about what we don't know.

The optimistic person (in philosophy called scientism) says "It is just a matter of time. Eventually, we will understand everything about the world. This island of knowledge will increase, increase, and increase, to the point where there won't exist anymore the ocean of the unknown.

" However, based on the arguments we just presented about technological limitations, instrument error, and the way in which knowledge increases, we know that these affirmations are totally absurd. There always be "the unknown. " See why: as the island increases, the periphery of the island increases too.

The limits, boundaries, between what is known and what isn't. That means that, as we know more about the world, more questions we can make about the world-- questions we couldn't anticipate before. Back to the telescope example Before the telescope, nobody knew that the moon has craters.

No one knew the Milky Way was made of stars, that it wasn't a cloud No one knew that Jupiter had moons. But when Galileo pointed the telescope to the sky and saw it all, we learned a lot of new things but also starting having new questions of reality. We started to learn more.

The same thing with the microscope: when you point it to a water droplet and see tiny little creatures, you start asking "Wow! What are these little creatures? What they do?

" You start making new questions. This is the mark of knowledge. Knowledge never has an end.

Its most fundamental characteristic is that it created not only knowledge but the unknown. Knowledge creates doubts. It creates new questions to be made.

Obviously, we won't ever know all the questions to be made. Therefore, we won't ever know everything. It is obvious, guys!

Because we can't even conceive what are all the questions to be made. So, the Island of Knowledge increases, but the ocean of the unknown is infinite. While we maintain ourselves curious to ask about what is new, we will keep growing as human beings.

We will keep elevating our curiosity spirit to higher levels. And a crucial detail: even in the ocean of the unknown, certain regions are unknowable. Unknowable means what we can't know.

Science can't answer all the questions. There is no doubt it is the biggest rational system to confront the knowledge of the natural world. It is unquestionable.

Without science, we would be lost. We would be in ancient times. We changed the world, our quality of life, our lifespan doubled over the past 150 years from 40 years to 80 years, all thanks to science.

No one is discussing the importance of science. But it is also important to understand that science, being a human creation, has limits. There are questions that science can't answer.

For example, we don't know if science can say something about the origin of everything, about the origin of the universe. We don't know how science can really reproduce life on earth. We can say when the origin happened.

But we don't know the details about how it occurred exactly. We can have hypotheses and theories but a final confirmation seems impossible. So, it's very important because it maintains ourselves humble about knowledge.

Yes, we increase our knowledge, we expand human horizons we grow because our curiosity gives meaning to our lives. Without our curiosity, we are, as Einstein said, as an unlit candle. We don't want our candle to unlit.

We want our fire to keeps burning forever. Our curiosity makes us humans. On the other hand, we need to understand: some questions go beyond what science can conceive.

What science can understand. Science has a methodology, a way to look at things that is not totally complete. And it's okay!

This is great because we can create a complementarity of knowledge. Look at things in many different forms. It is very moving because science dialogues with philosophy, history, psychology, sociology, arts, with all the forms of human creativity.

In a way that we can understand better who we are, in what world we live in, and why we are here. In the end, these are the big questions that make us human. That's why we are here on this Youtube channel.

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