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Universe and the Balloon
(Speculations on science and the nature of nature.)
by Henry Tjernlund 1999
So, really, how big is the Universe? Do you ever wonder that every time astronomers use a new telescope to look deeper into space they see more and more distant objects. Makes it sounds like the Universe goes on forever, doesn’t it? But, what about all that Big Bang stuff and the Universe expanding out from a single point to a certain size, the size it is now. (I’m not even going to talk about relativity and the concept of “now.”)
What am I getting at? Let me explain.
The current theory of everything (i.e. the Universe) has it starting as an immense explosion. Everything hurled outward and perhaps even space itself expanding to accommodate the “inflation” (as some refer to it) of the Universe. This explosion cooled as it expanded until matter as we know it formed and became stable in this cooler Universe. After some time irregularities lead to the formation of galaxies and clusters of galaxies. Within these galaxies stars formed from the dust and gas clouds, and so on and so on.
Why do we believe this current theory? Because it fits measurements taken by telescopes. Because it fits the observations of one E. Hubble. Hubble photographed distant galaxies and performed a special kind of observation called spectroscopy. The splitting of light into it various colors and recording it. Such recordings give astronomers information about the chemical composition of stars in galaxies. Different chemicals have different effects on light such as emission and absorption of certain colors depending on the chemical or element.
To make a potentially long explanation short, Hubble discovered that the patterns in the spectrums that he recorded from other distant galaxies did not directly match any known patterns from chemicals on Earth. Were other galaxies made of completely different “stuff” than what we know? Shortly Hubble noticed that the familiar chemical patterns were in fact in the recorded spectrums but they occurred in different colors than usual. In fact, they were consistently “shifted” toward the red end of the color spectrum. And just about every galaxy seemed to have this “shift” to one extend or another. Not only were most recorded spectrum shifted toward the red but the more distant a galaxy was the more the chemical patterns in the spectrums tended to be shifted.
Various ideas were considered to explain this “red shift” from diffuse interstellar gas that may colorize the light passing through it to some kind of gravitational effect that could sap some of the light’s energy shifting it to the red, less energetic, end of the spectrum. But, the idea that best fit the data, and seemed most plausible was that the light was experiencing a Doppler shift. A Doppler shift, as is explained in almost every astronomy book or television documentary, occurs when the source of a sound (or light) moves away or toward the observer. The observer then hears (or sees) a change in pitch (or color) of the sound (or light). In the case of sound it rises in pitch when it comes toward the observer, from the observers point of view. Like wise it falls in pitch when it moves away from the observer. In the case of light, rising in pitch is same as the color of light from the object shifting toward the blue end of the spectrum, again from the observers point of view. So if the light from distant galaxies tends to shift toward the opposite red end of the spectrum then it could mean, via Doppler shift, that those galaxies are moving away from the observer.
Well, if most galaxies are moving away from us, in all directions, then that implies the Universe is expanding. Here many books or documentaries use the rubber balloon analogy. Blow up a balloon until it is just barely inflated round. Use a felt tip marker and draw dots at a few points on the surface. Then continue blowing up the balloon until it is noticeably larger. Look at the dots again. You should immediately notice that they are further apart. What you may not notice right away is that the more distant two points were from each other the greater the differences in their new distances. In other words, not only do the dots move away from each other as the balloon is inflated but the further the dots are apart the faster the distance grows between them. This is consistent with the red shifts observed with more and more distant galaxies.
Okay, okay, so many of us have seen this over and over in television science documentaries and books. What is my point?
Well, as astronomers use newer and more powerful tools to see farther and farther they always seem to see more and more distant galaxies. It has been proposed that the Universe as a whole is curved, possibly like that of a balloon. What I am talking about is the idea that space itself is curved along a dimension that we do not perceive. A forth, or higher, spatial dimension distinct from the up/down, left/right, forward/back three dimensions that we know. Actually, this is the basis of Einstein’s General Theory of Relativity and works out quite well mathematically even though we can’t sense it directly. (Well, actually, we can sense it directly. The General Theory of Relativity uses this space-time curvature to explain what Gravity really is and how it works.) But, how this overall curvature of space is actually shaped on the grand scale is the topic of much debate amongst those who work on the problem.
But lets return back to the Universe and the balloon analogy. One of the ideas for the curvature of space is like a balloon. The idea is that space curves back on itself such that it forms a closed surface, in this other forth spatial dimension. In such a curved, closed surface, the Universe’s space would seem to go on forever but actually close back on itself eventually. One way mathematicians describe it is that the Universe would be of finite (limited) size but have no boundary (or edge). Like the dots on the surface of the balloon would see no end to the surface of the balloon and it would seem to go on forever and ever. In fact, if the light rays that the dots used to observe their universe also curved around and stayed on the surface of the balloon then a dot could possibly see itself by looking all the way around the balloon. Almost like a cartoon joke where someone looks in the distance and sees themselves from behind.
Now think about this. In this little curved universe the light rays are bent and travel along the curved surface. When an observer confined to this surface looks out at their little universe they see it go on forever. In fact they can look all the way “around” in the distance and see themselves. If the balloon is perfectly round they will see themselves in every direction they look. And they will see themselves again and again, copy after copy, as their curved light rays continue circling the balloon.
Do you see what I am getting at? Maybe, if something similar to this is happening in our own Universe then maybe some of these distant galaxies are our own that we are seeing from behind us. Maybe many of those distant galaxies are the same ones we see in other directions. Its just that we are looking all the way around the Universe and seeing the same things from different directions. Will they look exactly the same with the same patterns and relative positions. Not necessarily. Maybe the curvature of space is not perfect and smooth and some distortions occur. This could keep us from recognizing that the pattern of galaxies in one direction exactly matches a group of galaxies in the opposite direction and realize that they are the very same galaxies. Wouldn’t it ironic if our Universe turns out to be smaller than what we observe and we are simply seeing all the way around it, maybe even more than once around. Just something to think about.
BTW, curved surfaces have all kinds of weird and neat properties. Try taking a course Topology or Differential Geometry and see what I mean.
© 2003 Henry Tjernlund