If higher dimensions exist, they aren't what you think | Exploring Worlds Beyond Our Own

this video is sponsored by curiosity stream home to over 2,500 documentaries and nonfiction titles for curious minds in a previous video we saw that gravity can be explained by the curvature of four-dimensional space-time we used to have no idea what caused gravity or like why the Sun could attract the earth across the vacuum of space with no physical connection as we just had a mathematical model but it was Einstein's general theory of relativity that describes how mass bends the fabric of space-time that finally explained the why of gravity in what many regard as the most beautiful physical theory currently in existence but what soon followed was another theory that tends to surprise people when they first hear it this is Theodor Kaluza said that if gravity can be explained by the curvature of space-time then maybe the electromagnetic force an interaction that occurs between charged particles could also be explained by some underlying curvature the problem is that the four dimensions of space-time were already used up in order to explain gravity so Kaluza introduced the idea of a fifth dimension or a fourth spacial dimension that could explain electromagnetism and this became known as Kaluza klein theory this said that electromagnetism and how electromagnetic waves propagate through the vacuum of space could all be explained by ripples in an extra spatial dimension it seemed like Kaluza may have finally unified two forces of nature by just extending general relativity to include one more dimension and when Einstein was presented with this he at first had no issues with it and we'll see why in a minute now I know this sounds crazy and kind of out of nowhere but consider this in a previous video we saw that something known as the metric tensor can describe how any space is curved this mathematical tool can essentially determine distances between nearby points on warped surfaces being corrections when the Pythagorean theorem fails and this is what's needed to fully describe a curved surface the metric used in Einstein's general relativity looks like this a four by four matrix as this was needed to completely describe the curvature of four-dimensional space-time but we can use metrics for any dimension as you can guess a three by three matrix could describe how a three dimensional space is curved and so on so Kaluza tried something interesting and solved Einstein's equations in five dimensions and one step to accomplish this involved extending the 4x4 metric to a five dimensional one what he added was a row and column that incorporated something called the electro magnetic vector potential the one extra component was an unidentified scalar field that's not as important for a quick explanation like this so now the metric included the four by four space-time metric from before and extra terms involving electromagnetism which by the way fit perfectly because the electro magnetic vector potential did require four components pretty much just what's needed for the added dimension and what Colusa found was that when he went through with the math out came not only Einsteins field equations in four dimensions but now also Maxwell's equations for electromagnetism discovered decades earlier the idea of just adding a fifth dimension amazingly made the math work we're two seemingly different forces of nature fit perfectly together as a five dimensional field which would yield known equations of gravitation and electromagnetism this seems very promising but it wasn't long before a problem started to come up for example due to recent quantum discoveries Oscar Klein came along and changed things up a bit he said that maybe that fifth spatial dimension was actually curled up on top of our own universe where you can imagine our universe is the flat grid and those golden circles aren't extra curled spatial dimension existing all around us which by the way would be extremely small and just to note while these were animated like golden Tauruses or rings they're meant to portray flat circles since the is just that one extra spatial dimension but then when physicists tried to do things like incorporate the electron into the theory there are discrepancies between theoretical values and measured values such as mass or charge that could not be accounted for after a few years the clues of Klein theory was dead but it did start the real conversation of using higher dimensions to unify the forces of nature that occur in our universe it's said to be the precursor to current theories that go way beyond five dimensions and although we currently have absolutely no proof that higher dimensions exist the math says they just might which is where we're headed but first we're going to explore the fourth spatial dimension just a little bit more where we have a bit of tuition still at least when we make comparisons so as with any video going into higher dimensions we need to visit flatland this is the hypothetical world of flat creatures that can only see along a completely flat plane and have no concept of height or a third dimension so even if a 3d object were to visit the Flatlanders they could only see a cross-section technically just a line segment get larger and then smaller as the sphere interacts with inner world even though the intersection would be an entire circle that could only be seen from above the plane as you can see a 3d creature like us would have godlike powers to Flatlanders able to enter their world at any point and see everything at once even if the two-dimensional creature were in their version of a completely boxed in region blocked off from everything in their world we could still see them and interact with that space so just imagine you got in an enclosed box thinking you're safe well now a 4 dimensional creature let's say a hyper sphere could still see you and if it wanted it could enter that space at any moment from out of nowhere you'd only be able to see a 3d cross-section as it interacts with our world but just like before there's an entire higher dimensional creature who you're only seeing a little sliver of hopefully you're seeing the comparisons and how a 4 dimensional creature would have godlike powers to us now if we could take that flatlander out of its two dimensional world and show it ours it would be a very weird experience the flatlander would only see an infinitely small sliver of our world at a time as we moved it in the third dimension things would weirdly change colors and they'd have no grasp from what's really happening they could see our world but only the tiniest bit at a time there's no way for their brain or eyes to appreciate the beauty of the 3d world and while we cannot imagine a four spatial dimension beyond the three we know of we can use similar analogies where if a 40 creature took us on a little adventure of their world whatever it would look like it would be very strange to us but we'd have no true appreciation for what it really was and there's nothing I or anyone can do to change this beyond finding the weirdest stock footage that I can then another interesting property in the fourth dimension is what it's like to invert objects in two dimensions if there's a flatland are on a piece of paper it can only turn and move side to side but if I pull it up into the third dimension flip it and put it back I have now completely inverted the object in a way that's impossible for it to do without access to a higher dimension the flatland creatures alone could not accomplish this but now just imagine this extended to us if you were lifted into the fourth dimension and flipped over in that dimension and then placed back into our three-dimensional universe you would be completely inverted your heart would be on the wrong side of your body any birthmarks would be on the wrong side and you would just be a completely mirrored version of yourself something that could not be accomplished by us alone in a 3d world so yeah that's basically the weirdness of the fourth dimension now although the idea of one extra spatial dimension predicted by Clues and Klein did die out the idea of extra dimensions did not it's very much alive and today the most promising theory that would use extra dimensions to unify the fundamental forces is string theory string theory replaces the idea that point-like particles such as electrons or neutrinos and so on make up our universe and instead says that on a much smaller scale if you zoomed in a lot each particle is just a vibrating string and it's the vibrations of those strings that determine the properties we observe like mass charge and so on pretty much particles are really just the same string playing different notes and it's the variety of possible notes that account for everything we observe in our universe see there are four fundamental forces of nature the strong nuclear force that holds the nucleus of an atom together the weak nuclear force responsible for radioactive decay of atoms the electromagnetic force that causes charged particles to repel or attract each other and then gravity three of the four of these can be described with quantum mechanics but gravity is the odd one out at the moment gravity cannot be explained at the quantum scale where quantum effects can't be ignored as in quantum mechanics and general relativity don't seem to get along and thus we have not unified all the fundamental forces of nature but string theory says that one of the vibrations of these tiny strings that make up our universe yields the graviton a particle that carries gravitational force and this explanation would finally describe gravity according to the principles of quantum mechanics just like the other three forces no we have not detected or discovered these so right now this is speculation but this could be what helps us create a theory of everything but it's the mathematics of string theory where things get interesting because as you can guess the math says that higher dimensions not just might exist but are required to exist in order for string theory to work in fact if strings only existed in three or four dimensions then string theory wouldn't unify the laws of physics as we hope that it should how many dimensions that are predicted kind of depends on which specific part of string theory are looking at for example bosonic string theory predicts 26 dimensions super string theory predicts ten dimensions and M theory predicts eleven dimensions now all the sources I could find say it's extremely difficult to explain why these dimensions are required without getting very technical many will just say that meaningless or unwanted terms appear whenever you do the math but they go away when you fix the dimensions to ten or twenty six for example in those dimensions the math just works out among all the mathematical jargon though you'll encounter something called modular forms a lot and something more specific is Ramanujan's theta function which has direct applications to string theory physicists say it's deep within this kind of math that you find why extra dimensions must exist but these definitely aren't trivial and aren't met in for a video like this what we can talk about though is how the extra dimensions that are predicted aren't what you think we talked before about a four dimensional creature taking us on a tour of their universe but that isn't what theories predict physicists believe not that there are these higher dimensions that are large and extend beyond ours rather the extra dimensions are very small and curled up and by very small we mean similar to the length of a string close to something like 10 to the minus 30 a--the meters in fact we saw this before with clues of Klein theory that one extra spatial dimension mean curled up on top of our own as in this extra dimension would exist everywhere around us but it'd be too small to experience meaning as you move your hand through the air you'd essentially circumnavigate these dimensions unable to really them due to their size to give some more intuition of this physicists commonly used the analogy of an ant on a cable from far away the cable seems one-dimensional to us and to quantify where the ant is you just need one number the distance from one of the ends like it's a meter stick but when you zoom in there's another dimension the ant has access to it can move around the cable in that circular path there's another dimension that's curled up which isn't noticeable from far away it's not an extended dimension like that of the cable itself or a sheet of paper but the extra dimension is there and just curled up in a way that only a small creature has real access to so if there are extremely small dimensions curled up everywhere around us we would not have access to them but you know what would extremely small objects like maybe strings that make up the smallest elementary particles we know of these could vibrate in those higher dimensions however we said that strings need much more than three four or even five dimensions to vibrate in so instead of the one extra curled up dimensions addicted by Kaluza and Klein some physicists now say there may be very small six dimensional shapes curled up all around us known as khalaby Yau spaces the geometry of these and how they're intertwined is actually critical in string theory because the geometry of the actual dimensions plays a role in determining how the tiny strings can vibrate and remember the specific mode of vibration corresponds to a specific particle and its properties and if you're wondering why six dimensions just remember that on top of the four dimensions we know of three space in one of time adding six more makes ten dimensions which is what we said super string theory predicted but a follow-up question that may come up is why would there be six curled up dimensions but four dimensions that are extended and as with many of these theories we don't know one idea is that all the dimensions were curled up and when the Big Bang happened four dimensions expanded but six did not creating the universe we live in now but either way string theory does predict curled-up extra dimensions different from what we're used to and string theory doesn't just explain elementary particles but space-time as well in fact when physicists went through the mathematics of string theory Einstein's equations emerged like by magic this happened without assuming any of his equations to begin with and it completely shocked physicists at first even one said it would have been totally possible for us to discover string theory first and then use that to derive Einstein's equations so we'll string theory be the thing that changes the way we see the universe and do these other worlds exist beyond ours we just don't know at the moment deep within the math we find things that give us hope for we've discussed here but how close we are to experimentally determining any of this is very much up for debate now beyond what was shown here there are so many more strange theories that exists like physicists have talked about the idea of an extra curled dimension of time whatever that would look like and how that could help explain our universe there's the idea that black holes lead to parallel universes and so much more if these types of things interest you I'll provide some resources below you can also learn plenty more over at curiosity stream who I like to thank for sponsoring this video curiosity stream is a streaming service that hosts thousands of documentaries and nonfiction titles spanning history physics and the universe technology nature and plenty more if you enjoyed the content of this video then you will not be disappointed by what they have to offer for example their horizon episode of parallel universes include several of the topics we discussed here and much more you'll explore the different versions of string theory in more detail and the reasons for the extra spatial dimensions they go into whether there was time before the Big Bang why the idea of an 11th dimension was such an important discovery and of course could there be parallel universes beyond our own founded by John Hendricks aka the founder of the Discovery Channel curiosity stream is an extremely affordable streaming service and only $2.99 a month now satisfy anyone with a strong desire to learn explore and understand the world and universe around us the service is available on a variety of platforms worldwide including Roku Android Xbox one Amazon fire Apple TV and more then if you go to curiosity stream comm slash major prep or click the link below and use the promo code major prep you get your first month's membership completely free this gives you unlimited access to top documentaries and nonfiction series that I know many of you will find very interesting so again links are below and with that I'm going to in that video there if you guys enjoyed be sure to LIKE and subscribe don't forget to follow me on Twitter and join the major Facebook for updates on everything hit the bell if you're not being notified and I'll see you all in the next video

Channel: Zach Star

Views: 1,464,904

Rating: 4.9065628 out of 5

Keywords: majorprep, major prep, extra dimensions, higher dimensions, hidden dimensions, what do higher dimensions look like, higher dimensional world, other worlds, string theory, general relativity, curled dimensions, flatland, 4th dimension, fourth dimension, what are higher dimensions, spacetime, theory of everything

Id: mmtLgYVEuJs

Length: 15min 45sec (945 seconds)

Published: Wed Jul 31 2019