Our seventh prompt comes from GM. They ask:

*Could there be other dimensions in the world that our human brains currently cannot see/feel/hear/touch/smell?*

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GM,

I’m happy you asked this question for two reasons – one is that I love talking about space-time, and the second is that your primary question was a personal one, and as per the rules of this experiment, I shan’t be answering those.

Onward. In math and physics, the dimension of a space or object is the minimum number of co-ordinates needed to specify any point within it. A point, for example, has no dimensions. Next, let’s think of a line. A line is unidimensional because you only need one co-ordinate to specify a point – say you have a 10 centimetre line and you divide it into ten, point 1 is at the one centimetre mark, point 4 at the four centimeter mark and so on. A line only has length. To move from dimension zero to the first dimension, you just need to have any two points and connect them with a line.

Now let’s think of a square. You need two coordinates within it to specify a point because a square has both length and width (or, to be more scientific, latitude and longitude.) To move from the first dimension to the second, you just need to have any two lines and connect them with additional lines (which will give you any number of shapes.) Then, let’s think of a cube, which has length, width and height. To specify a point within a cube, one needs three co-ordinates, one referring to length, another to width, and yet another to height. To move from the second to the third dimension, you just need to connect any two two-dimensional spaces/objects with additional lines.

Human beings experience life in three dimensions – we perceive height, width and depth, and most of the objects that surround us have these three parameters. These are the three dimensions of space we experience, and we can move back and forth in any of them. However, we only experience one dimension of time, meaning that we experience time in a linear/progressive manner. Think of time as a line. In this three dimensional world we live in, we are moving in one direction with regards to time – we are still unable to move back and forth in time.

We also only need one co-ordinate (as far as we know at the moment) to refer to time – say 9^{th} May 2017, at 5.27pm. That is the time at which I am writing this. Of course I have used many different units of time (we do this for the purpose of simplicity) but it is possible to state how many years/months/days/hours/minutes/seconds/milliseconds into our own existence (or the existence of our world/universe as we know it) that something is happening. We also can’t hop back to the 1960s for a quick look at what is happening there like we can walk back down a road to see a fight that’s happening there.

Time is the fourth dimension, which is why we talk of space-time. Because we experience space and time simultaneously. Which is why you (and I) are always located at a specific point in space-time known as an event. We need four co-ordinates/parameters to identify an event – the three dimensions of space (that is, height, width and depth) and the time. Think of your last birthday. You (probably) know the time it occurred, as well as where you were when it did. We tend to think of our lives in terms of events.

Now, let’s think about the possibility of more dimensions. Arguments have been made for as many as 10 dimensions (see here), and with good reason. I strongly believe that further dimensions exist.

We are beings in a 3D world experiencing four dimensions (three of space, one of time). Hence in a 4D world, we would experience (theoretically) three dimensions of space and two of time. If we lived in a four dimensional world, for example, we would move past experiencing time in one dimension as we do (progressively), to being able to move back and forth in time. That means that we would be experiencing time in two dimensions. Because of this, we could hop back to the 1960s to see what’s happening there with the same ease with which we walk back down the road to witness a fight (hence a time machine would allow us access to a four dimensional world that we cannot experience from our 3D reality.) This, of course, gives rise to the grandfather paradox and would allow the craziness we saw on the movie Predestination.

In a fifth dimensional world, we would now experience three dimensions of time. Imagine that – this enables many possible worlds and outcomes, and supports the theory of parallel/multiple universes. Think of Schrodinger’s cat, for example – before we open the box to unveil the cat inside, we don’t know whether it’s dead or alive, or both (known as quantum superposition), but once we do, we know for sure. In the same way, in this world, you may have missed your morning bus. But it is quite possible that there exists another world in which you also exist and got onto your bus on time. It is also possible for that world and this one to exist at the same time. This is known as the Many Worlds interpretation of quantum mechanics by Hugh Everett III. This interpretation theorizes that the initial universe split (and continues to split) into many other distinct universes (making it a multiverse) to accommodate each possibility. There is also the possibility that there are more than three dimensions of space (and of course, more than one of time) which is the basis of the parallel universes theory.

Which is not absurd considering that the idea that the multiverse (or universe if you reject that theory) is infinitely expanding is pretty solid. Remember, just because we do not experience or perceive a thing does not mean it is impossible/does not exist.

Ah, what a fine time for science!

[P.S. – GM, read Edwin Abbott’s Flatland. It’s free on Project Gutenberg, and dives into the concept of dimensions quite well.]

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**This post is part of a daily writing experiment that I’m running for a year. I’d love it if you took part! ?**