Anthropic principle, goodness where to begin with this one. This is a very broad theory so I will attempt to explain it in its simplest terms. There is the Strong Anthropic Principle (SAP) and the Weak Anthropic Principle (WAP), I am personally more a fan of the WAP but as you will see it is to me more based on what you believe as there could be a very good argument for both.
In general the Anthropic Principle has to do with how beings that live in the universe (humans) view their surroundings . It is kind of a circular argument so it depends on where you start. The SAP says that the universe is compelled to eventually gravitate toward conscious life to observe the universe that has come into being. One the other hand the WAP states that through basically sheer luck a universe that is capable of supporting life will eventually produce it. Then if the universe does produce life the beings that are able to observe it will marvel at its “fine tuning.” To me the main difference is that the SAP says that a universe will always gravitate toward supporting life and eventually intelligent life that will be able to observe the universe. Whereas the WAP states that life will happen only if conditions are basically perfect and the beings that arise in this universe will then be able to observe how mathematically improbable it is that I am writing this sentence.
This “Fine Tuning” is what we observe, and I talk about it below a little more, but we observe a universe that we believe is perfectly suited for intelligent life. The universe is just old enough for stars to have formed and gone super nova creating the heavy elements in the universe. Basically all your heavy metals were actually formed in the explosion of a super nova of a star. So here is the conundrum, if intelligent life were to have formed early in our universe they would not have been able to use any iron or titanium to use as building material to make a car or a space ship. There are other elements as well that are created in a super nova that could hurt a civilizations’ technological progress. To us it looks like we came along at just the right time, and everything is just right for our survival. So the point here is that we see the universe as extremely fine tuned for our survival and progress, whether or not that is true we may never know.
Like I said above this is a circular argument and I think both principles are near impossible to prove. Honestly, I think both could be correct, although I am still in favor of the WAP. I like to think that we are here and able to observe the universe just out of dumb luck. I have mentioned before that if something happened a fraction of a second either before or after it actually happened then gravity would have been too weak or too strong. If it were too weak then atoms would not be able to hold themselves together. If it were too strong elements that make up stars would be dramatically altered, causing them to burn thought their nuclear fuel at an alarming rate. If all the stars were burned out early in the universes’ time line, I would imagine that that would have a very negative impact on the formation of life. That also in my mind kind of puts the SAP to bed. How can a universe that has no stars support life, much less intelligent life?
I do not want to say this could never happen, although I do think it is highly unlikely. But I will say that I am a firm believer in the phrase “all things are possible, but not all things are probable.” So again I think it could be possible for a universe to harbor life without starts, I think it is highly, highly improbable. I cannot imagine what these creatures would look like much less how would they survive. What would they eat, how would they reproduce? Perhaps we are looking at this wrong, maybe they would not need to do any of these things.
Scientist are constantly amazed at the diversity of life on our own planet. In fact it was not that long ago that it was thought that all living things need the sun to survive. This “fact” was disproven with the discovery of worms that life around deep underwater thermal vents. There is also a microscopic animal called a Water Bear that can actually survive being in the vacuum of space without any protection. We only have one example of life that we know of, so I think it is beyond narrow minded to think this is the only way it could happen.
The Multiverse is a strange and fascinating place.