字幕表 動画を再生する 英語字幕をプリント How Many Next Dimensions Are There? Paintings are artistic representations of the world on a two-dimensional canvas. And for a long time, that's all that paintings could be. It wasn't until the Middle Ages when artists started toying with perspective and figured out that they could represent the three-dimensional world on a two-dimensional canvas. We similarly assume that our world has four dimensions, three of space and one of time, but isn't it possible that there are more dimensions we just haven't discovered yet? This is Unveiled and today we're answering the extraordinary question: How Many Next Dimensions Are There? Are you a fiend for facts? Are you constantly curious? Then why not subscribe to Unveiled for more clips like this one? And ring the bell for more fascinating content! Human beings perceive space in three-dimensions - length, width, and height. A line exists in one dimension because it only has length. A square exists in two, as it has length and height. And a cube is three-dimensional because it adds depth. A tesseract, on the other hand, is a geometrical concept that represents a cube in four dimensions. We can't accurately envision what this would look like, but just because we can't see something doesn't mean that it doesn't exist. A number of theories about the universe posit that we actually live in many more dimensions than we think. The holy grail of physics is a Theory of Everything that explains all the phenomena we see in the universe, reconciling general relativity and quantum field theory. General relativity, which focuses on gravity, does a great job of explaining the universe at large scales; and quantum field theory, which focuses on electromagnetism, the strong nuclear force, and the weak nuclear force, works well at small scales. (The strong nuclear force is what holds atoms together; the weak is responsible for radioactive decay.) The problem is, general relativity and quantum field theory are incompatible! String Theory is the leading candidate for a theory that combines them, providing a unified description of all four fundamental forces. In order to do so, it posits a whole bunch of other dimensions hidden from our view to make the math work out. But . . . where could they be hiding? Our first “new” dimension came when Einstein created his theories on relativity in the early 1900s. Previously, the world was understood geometrically as existing in three dimensions. But Einstein was struggling to explain electromagnetism until he considered time as a fourth dimension. The same principle was also able to explain gravitational fields. In his equations, all four dimensions are bound together in what we call spacetime. This provided a powerful new tool with more explanatory power and more accurate predictions than in Newtonian physics. It's a similar case to our painting example - there exists another dimension right alongside us, we just never realized it until Einstein's theories of special and general relativity. Immediately after Einstein's proposal, others thought about adding new dimensions to better explain our universe. In 1919, mathematician Theodor Kaluza tried adding a fifth dimension into Einstein's equations, and surprisingly, it fit perfectly. When trying to explain where this dimension was located, physicist Oskar Klein gave the example of an ant crawling on a hose. To the ant, it seems like he's walking on a two-dimensional object, but in fact there's a circular dimension on the inside of the hose right below the ant's feet. In subsequent decades, this idea underwent a series of revivals, as string theorists tried adding more dimensions to unify the forces of nature. According to superstring theorists, there are at least 10 dimensions in total: our four regular dimensions, and six smaller, compact dimensions that curl up in on themselves to form a structure called a Calabi–Yau manifold. While this structure is impossible to imagine in its entirety, there are 2D cross-sections of what it's thought to look like. Ten dimensions seems like a lot, but that's not even the most that physicists are willing to consider. The most popular variation of string theory is M-theory, which assumes 11 dimensions! Oddly enough, M doesn't stand for anything in particular, with Edward Witten, the theory's creator, suggesting that it could stand for “magic”, “mystery”, or “membrane”. Then there's also Bosonic String Theory, the original version of string theory developed in the 1960s. Bosonic string theory posits that there have to be 26 dimensions in total, 25 of space and one of time. While it may initially seem unlikely that we'd only be able to see 3 dimensions in a universe of 26, it may be analogous to the fact that humans can only perceive a minuscule amount of the visible light spectrum. If we didn't need to see these dimensions to survive, maybe we never evolved to. Again, what these extra dimensions are is impossible to imagine, but for now, physicists say they're rolled up and compacted in the Calabi-Yau manifolds. We just can't experience these dimensions because they're too small. Quantum mechanics adds another layer of complexity to the situation. At a quantum level, the world doesn't act at all how we expect it to, and things occur that are impossible to experience at the macro level. According to the many-worlds interpretation, quantum mechanics even calls for the existence of infinite universes. Strange as it is, this is actually a popular theory. Basically, quantum mechanics seems to show that at atomic and subatomic levels, physical systems don't have definite properties until they're measured; the many-worlds interpretation posits that in fact, all possible outcomes are realized, just in different worlds. Thus, there could also be many other “dimensions” in another sense: other worlds existing right alongside ours. Think of it like a length of rope - although it appears to be one long object, on closer inspection there are hundreds of tiny threads alongside each other. There's no telling yet how many dimensions there truly are. Mathematics shows us a number of possible dimensions, but that doesn't mean they're real. The problem with math is that it's extremely creative and abstract and can be consistent on paper without necessarily representing the material world. For example, we represent dimensions in math with coordinate axes. We usually have three: x, y, and z. But we can add dimensions as easily as adding more letters - even if it's impossible to draw. Proving their existence is another feat entirely. These extra dimensions may be too small to see, but maybe we do experience their interactions with our world. Some researchers have postulated that consciousness exists in another dimension - so it's possible that one or more dimensions actually exist in our own head, so to speak. Or perhaps death opens alternative dimensions to our comprehension, and the afterlife exists in its own dimension. Perhaps dark matter and dark energy hold the key to understanding where these other dimensions are, as both are completely invisible but account for most of the matter and energy in the universe. In fact, according to observations, observable matter and energy account for only 5% of the universe's total. If there are 26 dimensions, perhaps the rest is tucked away there! Either way, the fact that so many dimensions can feasibly exist in math highlights just how little we know about the universe. And that's How Many Next Dimensions There Could Be. What do you think? Is there anything we missed? Let us know in the comments, check out these other clips from Unveiled, and make sure you subscribe and ring the bell for our latest content.