"Professor, you are the fourth dimension." Sometimes I hear these words. It looks like someone with an unknown mental world. It is not inconvenient to look and live a little differently from the people of the world, nor does it affect the world badly or change the world physically even if it lives a little differently.
As a physicist, I have a strong desire to look into complex dimensions. But physics is becoming ever more complicated. There were times when one could publish a paper by solving an easy problem. Some people might blame my older age for feeling this way, but it is true that writing a paper has become more challenging. Are there only extremely difficult problems left that I haven’t been able to find answers for?
I have been driving a 15-year-old five-grade diesel car by subway. If you wake up in the morning and get off the escalator in the subway station, it feels like you are going down to another universe. At the moment of subway rumbling, in a rattling train someone sees a cell phone, somebody sleeps, some listen to music, others look at the ceiling with a blank face. We all go on a nice one-dimensional journey on the subway, and when the subway stops, we leave for our own space.
Humans are three-dimensional beings. We cannot metabolize in a two-dimensional environment. Humans with digestive organs require a four-dimensional space-time to secure continuity, which is a condition of being alive. Therefore, four dimensions are needed to explain the existence of humans. Space and time are integrated into one as if they are shadows of each other.
We may not notice visible changes, but the era of new perspective and paradigms are soon arriving. Superstring theory and M-theory are close to being completed. The two physics theories explain that the space of the universe is not three dimensional as one may expect. Rather, it exists in 11-dimensional hyperspace. According to the theories, various particles and matters in the world are composed of membranes and we recognize their individual shapes based on their patterns of vibration.
Do we really need these theories that are so hard to wrap our heads around? Life is already tough as it is. However, such theories are the only way to understand the existence of the universe and us humans. Humans are smaller than a speck of dust compared to the vast size of the universe and the world that can be witnessed through human eyes is limited—even the round Earth looks flat to us. As a three-dimensional building appears in straight lines, the universe is spread across such an extensive space that it looks like a four-dimensional space-time to human eyes.
There must be space-time continuums in the universe that organism on the Earth living in a four-dimensional environment cannot experience. Four dimensions are enough for humans, but what are space-time continuums that are out of our reach? Ancient people believed that the Earth was hoisted up by elephants and the sun revolved around the earth. Now, we are heading towards a more expansive perspective of 11 dimensions from our usual four dimensions. I wonder if it is the world changing while we stay the same or it is us that are changing.