Chapter 14: From Order to Chaos

Although we believe otherwise, everything has texture- nothing is completely smooth. Even though it may feel smooth to the touch or look smooth to the eye, nothing is completely smooth. When we consider a wooden table for example. To the naked eye, it looks completely smooth, and to the touch it feels very smooth, however, if we could magnify the texture of the table with a superfine microscope at and extremely high magnification, we would realize that it is not smooth. Really, the table would look like a vast space of hills and valleys. The same can be said about the Universe. When we look at the night sky, it appears to be completely smooth and homogeneous, but on an extremely small scale, its constituents would not appear smooth. If we could see the Universe on such a scale, we would see the space between particles, and we could see that some areas are more dense or empty than others.

The Universe looks homogeneous from afar, but it in actuality, it is very structured. When we view the sky we can see some stars and maybe even a few planets depending on where we situated in relation to their positions. As we judge from a larger scale, we see that we are embedded in a galaxy, and that galaxy resides in and amongst a larger galaxy. From even further away, we see that cluster of galaxies is seen as many clusters composing a massive network of filaments, walls, and nodes of light. If we observe this from very far away, it appears as if all of these irregularities blend into one faint, smooth texture.

When we look at the surface of a table, a piece of material, or even the surface of the Earth, it appears that the farther away we move, the more indefinite textures become. When we view the Universe, we are confined to the Earth, so we can’t move further away, we can only move closer. The closer we get, the more irregularities that are present, and the more we realize that the Universe is simply not smooth.

Since the 1970s, it has been possible to measure angular positions of galaxies in the sky. These observations relay that galaxies tend to be evenly distributed throughout the sky. There aren’t any preferred directions in the sky, which is expected if the Universe is homogeneous. It is not only possible to measure the angular positions in the sky, but also the distances to galaxies. As we can recall from a previous chapter, we know that a red shift is a measure of how fast a galaxy is moving away from us; Hubble’s law tells us that the more distant a galaxy is, the faster it moving away from us. Therefore, we can use the angular positions and the red shift to construct a three-dimensional model of the galaxies.

The most compelling evidence for homogeneity is relic radiation. Homogeneity implies that the Universe cooled at exactly the same rate at all points in space. Basically, the rate at which hydrogen and helium captured electrons was the same at all points in space. The left over radiation must have had exactly the same temperature everywhere. The smooth collection of radiation is an indication that the Universe was smooth in the past. This is the strongest evidence for a homogeneous Universe. A rough Universe on small scales appears smoother and smoother the farther away we move from it.