The Universe is very, very big…I think we all know that. Probably most people don’t think about that very much, as it doesn’t really impact their everyday lives. But I’ll bet that a significant number of us love to think about it, and find it a source of awe and wonder.
And some that think about it seem to find it existentially disturbing. A good example is the attitude consistently expressed by the great cosmic horror writer, H. P. Lovecraft, whose stories often refer to "vast gulfs of time and space”, and tend to regard human beings as insignificant when compared to the vastness of time and space.
In his short story “The Call of Cuthulu”, Lovecraft begins with:
“The most merciful thing in the world, I think, is the inability of the human mind to correlate all of its contents. We live on a placid island of ignorance in the midst of black seas of infinity……some day the piercing together of dissociated knowledge will open up such terrifying vistas of reality, and of our frightful position therein, that we will either go mad from the revelation or flee from the deadly light into the peace and safety of a new dark age.”
Lovecraft combined this feeling for the awesome sweep of space and time with a sort of gothic blackness along with a distinctly misanthropic tendency. In particular, one feels that to some extent he was using the hugeness of things to show how puny the affairs of humans are. This is, I think, a bit of a fallacy, because our importance (or lack thereof) should not really have anything to do with our relative size.
The attitude that the magnificent size of the universe does render us insignificant is brilliantly spoofed in Monty Python’s film, “The Meaning of Life”, in the “live liver donor” scene: in this skit, some medical technicians collecting organs from donors try to convince a woman to let them rip out her liver while she is still alive. To persuade her, they materialize a guy (Eric Idol) in a vested suit who sings a catchy song to her about the dimensions of the cosmos. Interestingly, the lyrics to the song appear to be based on, for the most part, reasonable estimates of galactic and cosmic parameters. The skit can be viewed on the web, and the lyrics to the “Galaxy Song” can be found at many sites. My interpretation of this scene is that it shows that our personal pain and agony are real, essentially filling ones "subjective universe", and the size of the universe is irrelevant to making a decision involving subjecting oneself to live liver removal.
In the case of Lovecraft, I think there was a another attitude at work with him, in that he was truly fascinated by physics and cosmology (probably way ahead of his time in that regard) and his cosmic horror fantasies allowed a playful way for him to indulge the emotion and to stretch his imagination.
Another person who made some relevant remarks about the dread that can accompany thinking on the cosmos, and man’s place within it, was the French philosopher Blaise Pascal. For example, some of my favorite Pascal quotes (taken from his work “Pensées” of 1670) are:
“Man is equally incapable of seeing the nothingness from which he emerges and the infinity in which he is engulfed.”
“Through space the universe grasps me and swallows me up like a speck; through thought I grasp it.”
“[I feel] engulfed in the infinite immensity of spaces whereof I know nothing, and which know nothing of me, I am terrified. The eternal silence of these infinite spaces alarms me.”
Note that, in that last quote, Pascal throws in the interesting twist that it is the “eternal silence” of the spaces that he finds scary. I wonder if by that he meant that we earthbound animals seem to be totally alone? Or did he mean something else by it? In any case, I find it to be a nice poetical touch.
I think everyone can agree on the utter impossibility of really comprehending the galactic and cosmic sizes and characteristic times the way we would with most everyday objects and events. However, we can write down the numbers, and, in a way, understand the magnitude of what is involved. The use of analogous ratios can help put things in some perspective, and give some insights. Some of these will be considered below.
Based on information gleaned from various wikipedia sites (1,2), the following are some of the dimensions characterize galaxies and the cosmos:
(1) A typical galaxy diameter ranges from 1000 to 100,000 parsecs, or about 3000 to 300,000 light years. This is about 20 million billion miles at the small end of the range…wow, an inconceivable distance, really.
(2) A galaxy can contain anywhere from 1E7 to 1E12 stars…that is, ten million to a trillion.
(3) A typical spacing between galaxies is even bigger, perhaps about 1 Mega-parsecs, or 3 million light years. Thus, the distance between galaxies is about 10 to 1000 times the size of a galaxy.
(4) The number of galaxies in the universe has been estimated to be about 1E11, or a hundred billion (the Monty Python song actually overestimates the number of galaxies as being “millions of billions”---so maybe hold on for giving up that liver!).
(5) The average density of the universe is very small, about 30 orders of magnitude smaller that the density of water.
(6) The estimated radius of the “known universe” is 46 Billion Light Years.
A number of amusing examples can be considered to give some insight into these facts.
The average size of an atom (e.g., Helium) is about 100 pico-meters (or an angstrom, 1E-10 meters). The spacing between molecules in a gas at 1 atmosphere is about 3 nano-meters, or about 30 times the size of an atom. It is amusing to note that this is in the range of the ratio of a larger galaxy to a typical inter-galactic spacing.
How long would it take for a jet airplane to cover the distance equal to the diameter of a typical galaxy? If we take the small end of the range, 20 Million Billion miles, and consider the plane to fly at a steady 500 mph, this is over 4 billion years. Longer than the time that life has been on the earth. Indeed, it takes 3000 years for light to cross it, which of course is what 3000 light years means. And since a jet flies about a million times slower than light speed, it takes it a million times longer to traverse a given distance. If we consider a plausible spacecraft traveling a hundred times faster than a jet, it would take it a mere 40 million years to cross this ‘small” galaxy. We can see that any kind of conventional spacecraft will not be able to do the kinds of exploration depicted in the Alien movies. Now, if Star-trek like “warp speed” or worm-hole travel becomes possible, who knows what the limits might become (maybe there would be none).
So, a galaxy can contain a trillion stars. Consider the human body—according to most of the web sites (do a google search on “how many cells in a human body”) there are about 50 trillion, more than the number of stars in the largest galaxies.
According to point (5) in the above list, the average density of the matter in the universe works out about to correspond to about one hydrogen atom per cubic meter. (Cosmologist Alan Guth has been quoted as saying that this is about 10 million times a better vacuum that can be attained in our laboratories). This low density seems to suggest that the universe is mostly nothing. If one can buy that, the answer to the old puzzle, “Why is there something rather than nothing?” would be, “Well, it is nothing”. Maybe that would be an amusing quip. But seriously, there are significant regions of the universe where “something” is clearly happening….not only galaxies and black holes and Quasars, but the amazing, seemingly so unlikely, phenomena of life (at least on one planet that we know of).
Now consider the range of the number of stars (1E7 to 1E12) in a galaxy. If we scale the population of Tokyo (12 million) to the larger number, then the smaller galaxy corresponds to about 100 people. Hmmm….we wouldn’t call that a city or even a town, really. Makes you wonder if cosmologists are right in classifying the small guys as galaxies?
But another kind of vastness arises when we consider how small things can be. If string theory is right….I have no idea if it is, nor, I suspect, does anyone else….then the smallness is equally baffling, and can be somewhat scary also. According to string theory, the characteristic dimension of strings is ~ 1E-35 meters, about 20 orders of magnitude smaller that the nucleus of an atom (a proton or neutron, of which several make up a nucleus, are about a femto meter, 1E-15 m, in extent), and this in turn is many orders of magnitude smaller than the typical size of atoms (1E-10 meters). And bigger yet, though still small by macroscopic standards, a typical human cell has a characteristic dimension of the order of ten microns.
A fascinating video, “Powers of Ten” can be watched on the Internet. It is based on a program and a book created by Philip and Phylis Morrison. This brilliant show takes you in steps of ten in both directions from the human scale dimension of one meter, down to the string theory dimension of the small side, and up to cosmic dimensions on the big side.
There is something about all of this that I find stranger, or perhaps I should say more unsettling, than the awesomeness of all these cosmic scale comparisons. Namely, that there must be countless trillions of planets out there that are solid like our planet, and contain rocks, mountains, and maybe even some water. Although some tiny fraction of these might support life, probably the vast majority of them do not, and in fact no conscious observer will ever see any aspect of them from close quarters, or walk around on them. And yet, if any of us were there, we could see them, touch them, etc (provided a suitable space suit environment were provide us, of course). It makes you think about the objective reality of the physical world. Is it really “there”, if no one ever sees it? I suppose I believe it is, but it gives me an odd felling. Much the same feeling is evoked in thinking about our planet in the millions of years it existed without any life yet present. Yet all of that time the wind blew, seas and storms raged, and so on. It suggests something along the lines of the old puzzle “If a tree falls in the forest and no one is around, does it make a sound”? Many regard such a question as silly, or rather one that just requires an analysis of what is meant by “make a sound”…..but to me the question is not so silly, and makes us dwell on what is meant by objective reality. In what sense are all of these portions of the universe that will never be observed objectively real?…does this kind of thing perhaps hint as to why consciousness exists?…that is, does it suggest the necessary, or at least important, role of conscious observers? But in any case, at the present time and into the near future, all of us humans, no matter how well traveled or worldly we are, will observe and interact with only the most minute portion of the universe.
Perhaps the most amazing thing about all of this, and I find it emotional to think about, is that we human beings have evolved from apes in just a finite number of generations (an almost "countable" of them, perhaps on the order of a million) …and we remain genetically very similar to chimpanzees, according to most evolutionary biologists. Isn’t it stunning to realize that we, related so closely to our ancestral apes, can now can grasp some truths about the physical universe, a universe that is so far “out there” from us and in a sense so far below us in size. I am sure that at the present time there is still much to learn. I know a lot of people, outside of science usually, that seem to almost enjoy gloating about how “we really don’t know much of anything”. Well, for my money the human race will continue to learn more about physical reality, and it will continue to amaze us, and the more stunning it will be the more that is learned.