# The 4th dimension

People of often tell me that I think too much. Maybe that is true, but at least I am prepared to think big. Today I am pondering the nature of the Universe. At the weekend I saw a T-shirt with a slogan printed on it: “Too stupid to do science? Try religion.” Although I am not religious myself, I could easily see how this might cause offense! It got me wondering whether there is a conflict between religion and science …

There are plenty of questions about the Universe. Was the Universe created? If so, why, how and when did this take place? What about its end? Does it have a purpose? Can all its detailed structure and history [and future] ever be understood by us mere mortals? Science tries to answer these questions – or, at least, provides the tools to pose the questions more precisely, hypothesize about the answers and develop and test theories. Religions tend to go for the “God did it” kind of answer.

The most powerful tool we have to aid understanding of the Universe is mathematics. There are plenty of things that the human mind cannot conceptualize. A good example is anything beyond three dimensions. Imagine a cube of material. That is easy – it is just a box shape with all three dimensions the same. Now, what about a similar 4-dimensional object – a hypercube? Can you imagine such a thing? No, I am unable to do so – it is not just you. However, I can grasp the idea of a hypercube from a mathematical perspective, as the mathematics is quite straightforward. The volume of a cube of side x is x^3 [x cubed]; for a hypercube it is simply x^4. This means that I can write equations for objects of any number of dimensions, even if I cannot possibly visualize them.

OK, so now, when scientists talk about the Universe as having, say, 10 dimensions, we can all grasp the idea in so far as we can do the mathematics. However, for me, there is a sticking point: time …

We are told that our world, for practical purposes has four dimensions: three spacial dimensions and time. That seems OK, but time is very much the odd one out, as it just goes in one direction. We can move freely in the other three dimensions, but time just marches on in one direction and we have to go along with it. Our perception of time may change – some days seem very long and others whiz by – but that is just the vagaries of the human brain. Every second is the same period of time as the last one. [Please do not bring up the subject of motion at relativistic velocities. We can save that for another day.]

I had an idea. As I am not a physicist or astrophysicist or qualified in any way, you may feel free to shoot me down in flames [email or comment is fine], but, for the moment, I have the talking stick, so I will continue. My thought is very simple: The Universe is expanding and has done so ever since the Big Bang. This does not [simply] mean that stuff is flying apart, it means that the fabric of space [or spacetime, if you prefer] is expanding. So all three dimensions are getting bigger and we can do nothing about it. But, what about the 4th dimension, time? Is the relentless progress of time in one direction simply the manifestation of that dimension expanding?

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This article first appeared on the Siemens Digital Industries Software blog at https://blogs.sw.siemens.com/embedded-software/2014/01/16/the-4th-dimension/