You are here - or at least there. I know that, because you're reading this. However, many, if not most scientists have a bit of a problem with that. Apart from the fact that the Universe exists, which is a problem in itself, what does exist is so carefully set up that it seems to be crying out for an explanation. Physical reality at a fundamental level is based on two main theories: the Standard Model of particle physics and Einstein's General Theory of Relativity, which encompasses gravity. A few other things have to go into the mix, including some numbers to allow quantitative predictions of physical phenomena, i.e. how large or small they are. These numbers are called fundamental constants and can't be predicted exactly, but have to be measured. It's the values of these constants, coupled with the basic laws of physics, that determine if material objects can exist at all, let alone if intelligent life could have developed.
There are several numbers that need to have values very close to their actual ones for life to be possible. If the Universe just appeared randomly, why should all these values come together in the way that they do, such that we can exist to know about it? On the face of it, that seems very highly unlikely. It is very improbable that the Universe is such that you can possibly be reading this, or that I could have existed to write it.
One example is the strength of gravity. Although we feel it quite strongly and end up bumping ourselves quite nastily at times if we fall down, it is actually a very weak force. However, if it were only slightly weaker or slightly stronger in comparison to electric and magnetic forces, stars would operate in such a different way from how they actually are that life as we know it could not exist. Equally, the strength of the force which holds neutrons and protons together in the nuclei of atoms could not be very different from its actual value for the different chemical elements to exist, at least in large enough quantities for us to be around. There are many other examples of crucial numbers and laws which combine in a very precise way to make life possible at all. This is known as fine tuning.
The chances of intelligent life existing in a Universe that was not designed are so small that it almost seems scientifically as if it was designed for us.
Physicists worry about fine tuning. Why is it as it is? If the Universe were created by a designer (God) then it could all be explained. Otherwise, we have to find some other way around it. This is a big issue for scientists and philosophers alike and huge amounts have been written about it. One main explanation is that we necessarily have to be in a universe which allows us to exist, otherwise we wouldn't know about it. This is known as the weak anthropic principle and essentially says that we do exist, so we shouldn't worry too much about it. Given the inquisitive nature of scientists, that isn't really good enough for many of them, so there is another version - the strong anthropic principle. This says that the Universe has to be such that intelligent life would exist in it at some point; therefore, fine tuning must be as it is.
The strong anthropic principle as it stands implies that the Universe was designed for intelligent life, or even that it was pulled into reality by the need for intelligent life to exist. This seems to get very close to saying that the Universe was designed (by God). I have to keep putting God in parentheses because a lot of scientists and philosophers who hold even the strong anthropic principle still don't allow for his existence. One of the major ways around this is to suggest that there are vast numbers of parallel universes (together forming a 'multiverse'). Then every possible combination of values for fundamental constants and variations of physical laws will be found in one or other of these universes. Therefore, it is natural that we find ourselves in the one which allows for life as we know it.
That's great, because it means that we don't need to resort to talking about God to explain fine tuning - if the multiverse could have been created by itself, of course, which is unlikely in itself. However, the big problem with all of this is that there is no direct evidence of a multiverse and no obvious way of finding any. It's a great idea coming up with a theory that no one can disprove, but the whole basis on which scientific theories develop is that they have to be testable in a way such that they can be disproved if they are wrong. The multiverse, certainly at the moment, cannot really be considered a scientific theory in that sense: it is just a rather bizarre idea that can possibly be linked to the inflationary model of the Big Bang, but that's rather tentative itself, even scientifically speaking.
There is so much evidence that points towards the fact that the Universe and everything in it was the work of a creator God and that evidence tends to grow as we learn more. Therefore, there are also more and more complicated arguments developed to explain it away, but it never really does go away because God actually is the creator.
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