This analysis is based primarily on scientific discoveries during my lifetime, including many from just the past 10 years.  This will take some time to lay out, but I think it is worth it.

You are probably aware of the special features of the Solar System and the universe that allow for the existence of life as we know it.  What you might not know is that they go far beyond the so-called "Goldilocks" position of Earth around the Sun: not too hot, not too cold, but just right!  For instance, the fusion reaction that powers the Sun combines two hydrogen atoms into one helium atom, converting 0.007% of the mass into energy (per Einstein's famous equation, E = MC squared); yet if the amount of mass being converted to energy were 0.006% or 0.008% instead, the universe would either be entirely hydrogen or would have no hydrogen at all (and thus no water), respectively – neither of which would permit the existence of life.  One of the constituent particles in the atoms of ordinary matter is the proton; if they were just 0.2% more massive, protons would be unstable and would decay into other particles.  If the mass of another constituent particle, the electron (which has a very tiny fraction of the mass of a proton or neutron) were doubled, atoms would not exist either.  There are many more examples like this, but one has been discovered lately that calls our very existence into question without outside help.

Careful observation of galaxies outside our own Milky Way showed that the stars were orbiting so quickly that they should be flying out of the galaxies.  Over time, after accounting for all of the ordinary matter in a typical galaxy (shining stars, burned-out stars, planets, black holes, dust, etc.), scientists realized that some other form of matter must be present in great quantities that provides additional gravitational force to hold the galaxies together.  Since it is invisible, and no one really knows what it is, scientists refer to it as "dark matter".  Dark matter is not composed of atoms and does not appear to interact with ordinary (baryonic) matter at all, but there is evidently much more dark matter than ordinary matter.  Dark matter that is known to be present in enormous quantities includes particles known as neutrinos, but they appear to have virtually no mass and don't really solve the problem.  Recent experiments and observations have verified the existence of dark matter beyond any reasonable doubt.

In the late 1990's, using new orbiting observatories and detailed scientific investigation, the age of the universe was ultimately determined to a remarkably high degree of accuracy: 13.7 billion years.  The same measurements and observations that allowed for this estimate also confirmed the rate of expansion of the universe.  The prevailing theories about the Big Bang that formed the universe had been either that the rate of expansion of the universe is gradually slowing down due to the force of gravity, or that the rate of expansion would remain about the same and would continue indefinitely.  Instead, scientists unexpectedly found that the rate of expansion of the universe is accelerating.  Again, there is no explanation for this as yet, so the concept of "dark energy" was introduced as the force that is pushing the galaxies in the universe apart at an increasing rate.  (The existence of galaxies outside our own galaxy was proved conclusively by the renowned astronomer Edwin Hubble in the 1920's, and he is also credited with the discovery of the expanding universe, i.e., that these galaxies are rapidly speeding away from each other; the Hubble Space Telescope is named in his honor).  Dark energy is even more mysterious than dark matter, but the general consensus at present is that there is much more dark energy than there is dark matter.  An estimate that I saw this month said that the ratio of dark energy to ordinary matter is 15 to 1.

If you are keeping track, you might have noticed that all of a sudden, scientists know a lot less about what the universe is made of than they thought they did.  When I was young, it seemed almost certain that the stars in the various galaxies made up nearly all of the material in the universe.  This seemed reasonable, since the Sun constitutes 99.86% of the mass of the Solar System - and we weren't even sure of the existence of other planets until the 1990's, although the presence of other objects like black holes and interstellar and inter-galactic dust is more appreciated now than it used to be.  (Dust can be beautiful as well:  Those gorgeous photographs from the Hubble Space Telescope, more often than not, are composed mostly of dust).  In any case, recent calculations suggest that less than 1% of the universe is actually made up of stars.

Now, the curious thing about dark energy is that it, too, is finely tuned so as to allow for the existence of the universe and life:  The amount of dark energy is just enough to accelerate the expansion of the universe, but not enough to make the universe tear itself apart.  In this instance, however, the "just right" aspect of dark energy involves more than one half of the entire universe.  The Nobel Prize-winning physicist Steven Weinberg of the University of Texas has been quoted as saying:  "This is the one fine-tuning that seems to be extreme, far beyond what you could imagine just having to accept as a mere accident."

There is an alternate theory, in case you wonder why you are hearing so much lately about multiple universes (also known as the "multiverse") – and not just a couple of thousand universes either.  The idea is that the universe only seems to be special because we happen to be living here; and that there are or were many, many, many more universes where things are not hospitable to life at all (or even matter).  One estimate I have read is that there would have to be a googol times a googol other universes before the truly special nature of the universe starts to become something that could really happen by chance.  For those who don't know where Google got its name, it is taken from the "googol" that was named decades ago by the child of a famous mathematician for a very large number:  a 1 followed by 100 zeroes, which is also expressed as 10 to the 100th power.  Thus, a googol times a googol would be 10 to the 200th power.  To give you an idea of how many universes that is, the number of electrons in the universe is estimated to be less than 10 to the 90th power.

So, if you would prefer to "believe" in untold numbers of other universes rather than believe in God, be my guest.  Either way, the answer to this enigma lies outside of the universe.

Far be it from me to tell you how you should react to this information.  I am a Catholic convert, and that works for me.  However, if you think that the wonders of modern science have somehow made the idea of God obsolete, you should realize that precisely the opposite is true.

References:  Most though not all of this information came from an article in the December 2008 issue of Discover magazine that is posted on line at http://discovermagazine.com/2008/dec/10-sciences-alternative-to-an-intelligent-creator/article_view?searchterm=multiverse&b_start:int=1 .