From time to time it's been mentioned at this space that the universe is extraordinarily fine-tuned for life and that this fine calibration points to intention and purpose in its design. There are numerous examples of this almost unbelievable precision and whole books have been written on the topic. See, for instance, Hugh Ross' The Creator and the Cosmos for an easy to understand introduction.
In this post I'd like to try to convey a sense of the awe that scientists who study the cosmos (cosmologists) feel when they work with some of these delicately balanced parameters. Here's a description of just one of dozens that could be highlighted. It's called the cosmic expansion rate.
The universe since the Big Bang has been expanding outward at a particular rate of speed. If it were to have expanded too rapidly, matter would spread out so uniformly that not enough would clump together and galaxies and stars would never form. If it expanded too slowly, the universe would collapse back onto itself in a huge lump and no life would ever emerge. So the rate of expansion has to be just right in order for there to be a universe which could sustain higher life forms like ourselves.
How precise does this expansion rate have to be? The astonishing thing is that the rate is calibrated so delicately that were it to deviate from its actual value by more than one part in 10 - that's a one with 55 zeroes after it - no universe suitable for life would exist.
To give you an idea of how breathtakingly exact the balance is between a universe which can sustain life and one which cannot, imagine seeing a dime held against the night sky from a distance of 75 feet. The space covered by the dime at that distance would look like this if viewed through a very powerful telescope:
Each of those specks is a single discrete galaxy containing billions of stars. The orangeish one at the center is similar to our Milky Way. The whole sky is 27 million times the size of this patch and would thus contain 27 million times this number of galaxies, or about 27 billion galaxies.
These galaxies are enormously huge collections of stars. From one edge of our Milky Way to the opposite edge is 100,000 light years (one light year is 6 trillion miles). If we assumed that all the galaxies were on average similar in size to our own, and that they were strung end to end across space, they would extend for roughly 1.6 x 10 miles or about 2.6 x 10 millimeters.
A dime is about a millimeter thick. Suppose we imagine a stack of dimes stretching all the way across this vast expanse. Suppose our stack continued across another thousand billion, billion universes full of galaxies like our own strung end to end. If so, there would be about 10 coins in the stack. Imagine further that each coin represents a possible value of the expansion rate and that a needle points to the single dime in this unimaginably long skein that represents the value the rate must have in order for any universe to be such as to sustain life.
The rate of expansion is so fine that if the needle deviated from this coin by a only a single dime our universe would have long ago either expanded out of control or collapsed back upon itself. And this example of cosmic fine-tuning is just one of dozens of constants, parameters, and properties that have to be set with similar precision in order for the universe to be compatible with living things.
This sort of phenomenal exactitude is almost impossible to plausibly account for apart from an intelligence which sets the values deliberately and intentionally. To think that nature could have come up with such precision solely by chance, not just for one value but for dozens, requires an extraordinary faith in the power of chance.
Some scientists, reluctant to embrace the implications of the discovery of these finely calibrated values, have resorted to an explanation that posits, without any supporting evidence, the existence of a multiverse, i.e. a near infinite number of universes among which are worlds comprised of all possible values for these dozens of parameters. If there are a near infinite number of worlds then there must be one, it is reasoned, whose constants and forces have the values ours does.
While a multiverse is theoretically possible, there's no evidence for it. It is invoked simply to enable us to escape the conclusion that our cosmos is intentionally designed. The suggestion of a multiverse defies the law of parsimony that tells us that the simplest explantion of the facts is the preferable explanation. It also violates the principle that the accepted theory should be one for which there is at least some evidence rather than one for which there is none.
We have plenty of evidence, of course, that precision and fine-tuning can result from the actions of intelligent agents. But we have no evidence whatsoever either that fine-tuning on this scale of precision can result from sheer chance or that there are any universes out there besides our own.