At present, the level of human science and technology can not observe virtual particles such as light particles and gravitons. Only through the theoretical model of virtual particles, the calculation results are partially confirmed (in a certain energy interval). In other words, what kind of existence the light particle itself is, or in what dimension, is uncertain. We now call it a particle, but it is not necessarily a particle.

In addition, our understanding of the concept of size is only in three dimensions, but not necessarily in other dimensions. For example, can you imagine what it is like to unfold the earth in two dimensions? Don't think that like the map you see, the earth is actually solid! )