Many physicists observe that Universe seems to be carefully crafted to sustain life. Only slight changes to physical laws constants would make life as we know it impossible.
However, I think this is more like a case of selection bias. We observe these physical constants because we happen to live a type of life that is possible in this observable Universe.
Thought experiment
Let's imagine there are 4 Universes. I don't find too many arguments for the multiverse hypothesis, but let's imagine them for the sake of argument.
- First Universe is similar to our own Universe, it can sustain a type of life based on Carbon matter combined with various other atoms
- The second Universe has slightly different physical constants that makes Carbon links unstable. Still, life is still possible based on Silicon, including some humanoid intelligent beings
- The third Universe is way different, it consists mostly on anti-matter. However, intelligent life can develop based on Carbon anti-matter
- The forth Universe does not support atoms at all. It only supports quarks in combinations unknown in our Universe. However, a kind of intelligent life develops based on quarks.
In all those Universes, intelligent life can observe that their physical laws seems to be crafted specially to sustain their kind of life. However, each Universe has different physical constants. However, each type of life will observe their physical laws as suitable for life. They will also consider that physical constants from the other Universes would not be able to sustain life at all.
Therefore, it is a selection bias that we observe an Universe that is suitable to sustain our type of biological life. If we would live in one of the other 3 Universes, we would observe other physical constants, that would also look specially crafted to sustain that type of life.
Life
I will not detail here what can be considered life. Among the requirements, it has to preserve and replicate specific complex patterns (think DNA and phenotypes). However, it doesn't need to be Carbon-based necessarily.
For life to be considered intelligent, it has to be able to form complex abstract models about the nature and Universe, and likely reach the stage of reflecting on the physical laws constants...
Multiple Universes
There might be an infinite number of possible Universe, each having a different combination of physical constant values, that could still sustain a type of intelligent life.
Each such different Universe would develop a different type of intelligent life. And each intelligent life would wonder why the Universe is so fine tuned to sustains their type of life.
Again, I don't find reasons to believe in a multiverse, however we will see that the same argument can be sustained also for a single Universe.
A different Big Bang
If does not have to be multiple parallel Universes. If we believe that Universe emerged from something like a Big Bang, we can also imagine that slightly different initial conditions would result in slightly different physical laws, and some of them would also sustain a type of life - that can be very different from what we know.
If the Universe oscillates between expanding and collapsing, the physical laws might be different at each re-creation of the Universe. Another kind of life form might wonder how that their Universe is so well tuned for their kind of like. When the resulting Universe would be unable to sustain life, nobody would observe this.
We can imagine that our Universe is only selected from multiple re-emerged Universes, and we happened to live in one that sustain a certain kind of life suitable for the current physical laws. However, we don't even need to believe in Universe re-creation to imagine such "selection bias".
The right time
Even if there was only one Big Bang, we still be able to imagine a temporal selection bias. Maybe the laws of physics were slightly different at different stages of the Universe evolution. Maybe we are at the right age of the Universe to observe the current physical constants and therefore to enjoy the life we know.
It is also possible that physical laws at earlier times of the Universe have sustained a different type of life, that wondered about different physical constants that are suitable for their type of life.
If is possible that later evolutions of the Universe to sustain other kind of intelligent life types, with the same or slightly different observable physical laws.
The same physical constants
Even if the physical constants would be immutable from the beginning of the Universe, we can still be facing a selection bias. There could be an intelligent observer... only when intelligent life can exist.
We cannot eliminate the possibility that very different types of life exists in this Universe, even if the physical conditions are way different than on Earth - under the same physical constants.
A Universe that is not universal
In The Problems of Philosophy, Bertrand Russel observes that we can apply the induction principle, however we cannot possibly prove the induction principle. Therefore, we cannot prove that the same physical constants we observe in the known Universe are not slightly different in other "corners" of the Universe.
Over time, Physics has improved the physical models based on new observations. There is no reason to believe that we attained the ultimate image about the physical laws. Our physical models are simple enough that we can expect to be revised by new observations, like the Newtonian laws were revised by the Theory of Relativity, and later by Quantum Physics.
Is is only a leap of faith to believe that the physical laws are the same everywhere in the Universe. We can still have universal laws, while we can discover that some of our constants in the model varies with some unknown yet law - for example it might vary with the expansion of the Universe.
Arguments to believe in multiple types of life
The life as we know is sustains by Carbon-base biological automata. There is no reason that similar automata cannot exist in some other forms, even not based on Carbon.
In a previous article, I showed that infinite complexity can be produced, theoretically, by an incredibly simple automata, while is is harder to stop when the expected pattern will be produced.
As such simple automata is highly probable to appear randomly under various physical laws, it is only a matter of time to produce a type of intelligent life that would wonder about the laws of the Universe. And that life would be conveniently located in a corner of the Universe that sustains life.
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