A direct link to the above video can be found at http://youtu.be/pnNGT3ae5go
This is a discussion of ten proposed reasons for why critics of Imagining the Tenth Dimension are saying people shouldn't watch my videos. See part 1 here. See part 2 here. See part 3 here. See part 4 here. See part 5 here.
Reason #6: The fourth dimension is not a spatial dimension, it's a temporal one.
If there are ten spatial (or "space-like") dimensions, and theorists tell us "the fifth dimension and above are curled up at the planck length", then what are they really talking about? How is it possible to have three spatial dimensions, then add one temporal, then six (or seven) more spatial dimensions extending from that? It would make more logical sense if they said "the fourth dimension and above are curled up at the planck length", because then you would be continuing with an ordered hierarchy of spatial dimensions, one after another, and leaving time out of the discussion until you were done counting spatial dimensions. But that's not what they say. Why? With my project, I insist it's because we have a unique perspective on the fourth dimension. As creatures made out of 3D atoms and molecules deriving their energy from entropy-increasing chemical reactions, we experience the fourth dimension as having only one direction: the direction which moves us away from the lowest entropy beginning of our universe towards the highest entropy ending of our universe. But that doesn't mean the opposite direction isn't just as valid! With my project, I explain that if the ten dimensions are spatial, or space-like, then the first three are spatial, the fourth is a spatial dimension constructed from two opposing directions but which you and I experience in a unique "uni-directional" way, and the fifth dimension and beyond are spatial. Counting 3 apples, 1 orange, and 6 apples, and then saying I have ten apples would make no sense. Likewise, the fourth dimension is not just time, it's an enfolded structure often referred to as space-time. General relativity shows us how space-time can be bent and stretched, folded or warped with a wormhole or a black hole. It includes the dimensions below, and adds two new opposing directions just as you would see when you added any other additional spatial dimension, and that's how the point-line-plane postulate is used in these discussions. This is why I say it makes sense to include the fourth dimension in our counting of the spatial dimensions. But saying there is only one label you can put on the fourth dimension (or any dimension) is what both Henry and I discourage. These ideas can be quite easily related to the concept of 4D Minkowski Space, or what's known as the "Block Universe" theory. Here's a famous quote:
The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality. – Hermann Minkowski, 1908Do scientists say a 4D Minkowski Space is the same thing as a 4D Euclidean Space? No, but they're not that different. In fact one label they use is that it's "pseudo-Euclidean". But here's the thing: Minkowski's Block Universe - with every point (x,y,z,t) within it corresponding to a unique "state" for our universe - is what we're thinking about with this visualization, rather than 4D as a one-way "arrow of time".