The Shape of the Universe | Ruiping He | TEDxYouth@JLHS
URL: https://www.youtube.com/watch?v=KbC1OhJCz68 Video ID: KbC1OhJCz68 ============================================================ Ladies and gentlemen, imagine you're an Asian sailor standing sail on the vast ocean. As you gaze out at the horizon, you may wonder, is the world flat or it is something more? This simple question has echoed through the human history leading us on a quest to understand the fundamental nature of our world. Today we stand on the shoulders of those ancient thinkers armed with powerful telescopes and sophisticated mathematical models. And we're asking an even more profound question. What is the shape of the universe? For centuries, people discovered the shape of the universe. Ancient cosmologies as mirrors of human consciousness. Mythological shapes of the cosmos Mesopotamia cosmic ocean. Hindu brahda. The cosmic egg. The universe begins as a golden egg containing Brahama who divides it into heaven, earth and atmosphere. Chinese Inya and celestial spheres. Heaven is round like a shell. Earth is square like a chariot drum which is said by Zoen who is a waring states period philosopher reflecting confusion harmony. The idea of a flat universe seemed to be accepted at that time by everyone. However, things have been changed. Polish astronomer Nicholas caused an opera in the mid 16th century by suggesting the earth move around the sun. But however at that time people always believe the sun is around the earth which seems is quite a mistake to us. But at that time by the Christian taught people always believe that. However it was noted in the 16th century that comets move in such a way that would harsh crash them through crystal spheres. Replacing the spears was the idea of episcoples. Circles superposed on circles mathematically influencing each other to result in observe planetary motions. Finally in6009 German mathematician Jonas Kepler published his theory of planetary motion which established that bodies in our solar system moving orbit shapes like ovos rather than circles. The first shift in our thinking came with the advent of Ein theory of general relativity. This evolutionary theory described gravity not as a force but as a curvature of spacetime caused by the presence of mass and energy. In other words, massive objects like stars and planets actually bend the fabric universe around them. This concept opened up a whole new realm of possibilities for the shape of the universe. Instead of being a simple ex flat expanse, the universe could be curved in various ways. Just as the surface of the earth was a twodimensional curved space which we call a sphere, the universe could be a threedimensional curved space. There are three main possibilities for the curvature of the universe which are positive curvature, negative curvature and zero curvature. You can see the picture over there. A curvature is a state of being curved like this or the degree to which something is curved. The theory of general relativity allows three shapes or geometries for the universe. These are flat, closed and open which is similar to zero curvature, positive curvature and negative curvature. A universe with positive curvature would like the surface of the sphere. In this scenario, if you were to travel in a straight line in any direction, you would eventually end up back where you started, you have no boundary. It's a mind-boggling concept, but it's a possibility supported by some theoretical models. On the other hand, a universe with negative curvature would have a satellike shape. In this type of universe, parallel lines would diverge and the geometry would be quite different with what we learned today. The universe in this case will be definite stretching out forever in all directions. Then there's a concept of flat universe which which has zero curvature. In a flat universe, parallel lines remain parallel and the laws of ukidian geometry that we learn in school hold true. For a long time, scientists weren't sure which of these models describe our universe. But in the past few decades, thanks to the groundbreaking experiments like the cosmic microwave background, which we call it CMBB, radiation measurements, we made significant progress, such as a significant impact on the series of the formation of the cosmos and lensing current measurements. But the story doesn't end there. Even though the evidence points to a flat universe, there are still many mysteries and some questions we still don't know. For example, what is dark matter and dark energy which together make up about 95% of the total universe? Energy content of the universe. These invisible substances have a profound impact on the shape and evolution of this universe. Yet we know very little about them. Now you might be wondering why does any of this matter? What's the point of we learn this today? The truth is understanding the shape of the universe has profound implication for our understanding of cosmos and our place in it. It affects our theory about the origin and evolution of the universe as well as our prediction for the future. We're like goldfish trying to map our boat shape from within. But with quantum telescopes and AI cosmology, we're finally disfiguring space-time or gummy folds. The universe shape isn't about isn't just about geometry. It's a signature of reality itself. We actually find that the density of the universe is such that it expands in every direction without any positive or negative curvature. In other words, we can understand easily the universe is flat like the ground we are stepping on. As we continue to explore the universe, we are using more powerful telescopes and more advanced theoretical models. We're getting closer and to closer to unlocking the mysteries we never found in the past centuries. As far as cosmologist can tell, space is almost like really perfectly flat. The universe seems to be a threedimensional sheet of paper. The question of the shape of the universe is a reminder of how much we still don't know about our daily life, about the universe. But it's also a testament to incredible progress we've made in the past few decades and years. So the next time when you look up at the night sky, remember that this universe isn't just about the stars and the moons or the things we can see by our eyes. It's a vast, mysterious, and beautifully complex identity. And we are all part of the journey to uncover its true shape. Thank you.