Have you ever wondered whether or not parallel universes exist? And if they do, how is it possible? To answer this question, let’s take a look at the notion of dimensions. Dimensions are simply the different facets of what we perceive to be real. We live in a three dimensional world and are familiar with the components that make up the three dimensions – that is we see objects in our immediate world as having a length, width and depth.

However, it seems that the three dimensional world is not the limit. In the light of string theory, scientists now believe that there may be many more dimensions beyond the three we are familiar with. In fact, the string theory postulates that it could be possible that 10 dimensions exist in the universe.

If dimensions means through which we are able to describe reality, then the fourth dimension would be time. For example, a table has three dimensions in space, its width, breadth and height. It also exists at a point in time. Hence, time is the fourth dimension that captures reality.

The first ‘string revolution’ occurred in the early 1980’s, when Michael Green and John Schwarz discovered supersymmetric strings, more commonly known as superstrings. The remaining six dimensions are invisible to us but string theory explains why they exist. According to string theory, subatomic particles such as protons and electrons do not exist as particles, but in the form of tiny pieces of vibrating string too small to be observed (1 Planck length – about 1.6 x 10^-35 metres). Each string is 1 dimension and may be open or closed in a loop. Vibrations from the string corresponds with each of the particles and determine the particle’s size and mass. On a subatomic level, there is a relationship between the frequency at which something vibrates and its energy. At the same time, as Einstein’s famous equation E=mc^2 tells us, there is a relationship between energy and mass. Therefore, a relationship exists between an object’s vibrational frequency and its mass. When scientists started to analyse the mathematics of string theory, they found that certain equations would only make sense if there are more than 3 dimensions.

Based on this, in 1926, a physicist named Oscar Klein suggested that there are two types of dimensions. One is the visible 3D dimension that we can see and the other is the additional dimensions that are curled up and so tiny that they are all around us but we cannot see them.

Consider a cable from a distance. It would look like a single line because we don’t see the circular part that wraps around the cable, but if we zoom in and take the perspective of a little ant, we would be able to not only walk along the cable but also walk *around* the cable. Thus dimensions this small is impossible for us to see compared to bigger dimensions. Therefore, we may imagine the dimension as a grid and these extra dimensions as circles on a grid which become the additional dimensions that we cannot see.

Although scientists are still further investigating the notion of dimensions, the existence of dimensions beyond the three that we are familiar with is not sufficient evidence to prove that parallel universes exist. However, with the advanced technology we have today, a proper answer will surely be provided to us soon!

*Written by Shirley Tang, Year 12*