There's an article at Salvo by astronomer Hugh Ross that should fascinate anyone interested in chemistry, biology or the exquisite fine-tuning of the universe that makes life on earth possible.
It begins with a challenge frequently leveled at those who believe the universe is intentionally engineered by an intelligent agent to permit life to exist. If so, some who dissent from this view ask, why is the universe so vast? Why are there so many galaxies? Isn't such a huge universe wasteful when a much smaller universe would suffice?
Ross explains that a smaller universe would not have sufficed, and that the universe has to be as large as it is and as massive as it is in order for carbon-based life to exist anywhere in it. Ross' article can be summarized as follows:
In order for life to exist, at least life as we know it, there has to be carbon and oxygen, and in order for these elements to exist there had to be a very precise amount of mass to the universe in its early stages of development. Here's why:
At the beginning of the universe, shortly after the Big Bang, the universe was rapidly expanding. Since mass exerts gravitational pull, the rate at which the universe expanded was determined by how much gravity there was acting as a drag on the expansion and this was determined by the amount of mass.
As the universe expanded it cooled. At one point the cooling reached the temperature range in which hydrogen atoms, the only atoms that existed in the early universe, began to fuse together to form other elements. This temperature range is between 15 million and 150 million degrees Celsius.
How long the expanding universe remained in this temperature range depended on how much matter there was to slow down the expansion. Too little matter and the universe would have passed through this range too quickly to form much else besides helium. Too slowly, and all the hydrogen would have fused into elements heavier than iron. Carbon and oxygen would have been very scarce.
In other words, to get the elements necessary for life, specifically carbon and oxygen, the expansion rate had to be just right, which means that the gravitational pull slowing the expansion had to be just right, which means that the amount of matter in the universe had to be just right. That amount of matter happens to be precisely the amount of matter bound up in the stars and galaxies we see in our telescopes.
In order to allow time for the production of carbon and oxygen, but not too much time, the expansion rate had to be calibrated to the astonishing value of one part in 10^55.
To get an idea of how precise this is imagine a dial face with 10^55 calibrations (one with 55 zeros). Now imagine that the dial has to point to exactly one of those calibrations for the universe to have carbon and oxygen. If the dial deviated by just one increment no carbon and oxygen would form. That's breathtaking, but in order to achieve that degree of precision of the expansion rate the universe had to have just the amount of matter that is today bound up in stars and galaxies that it in fact does have.
Indeed, the total amount of matter in the universe had to itself be fine-tuned to an astonishing precision of one part in 10^59.
So, the universe has to be as big as it is and as massive as it is in order for us to be here in this little corner of a galaxy located in an even smaller corner of the universe. Little wonder that many people conclude that it can't all just be a cosmic accident, that there must be an intelligent mind behind it all.
Ross goes on to explain how the amount of carbon we find on earth is also fine-tuned. Just a bit more or a bit less carbon and life on earth would not exist, at least not life forms higher than bacteria. The article is not long and it's very much worth reading in its entirety.
Meanwhile, check out this video to get an idea of how big the universe actually is and how small we are. Each circle represents 10x the diameter of the previous circle:
