A Question of Forces

Recent computer simulations and research have shown that dim stars could likely form in a scenario where the weak nuclear force is entirely absent. Planets harboring life could exist in a closer orbit to these stars. So if the weak force is not required for life then why does our universe have it?

I think our current view of the conditions necessary for life my be too limited. I think life will find a way to exist, taking many habitats we may deem as harsh, and finding a way to thrive. The discovery of the tube worms at volcanic vents on the ocean floor may be a glimpse of this ability.

This question makes no sense to me! I could just as easily ask "manganese nodules are not necessary for life to exist on Earth, so why do they exist?". The answer (although one is hardly necessary) is that being necessary for life to exist is not a prerequisite for anything to exist. On the other hand there are probably many things that are a prerequisite for life to develop.

1) Thank you for your response, although I was looking for an explanation of the weak force and not precisely the emergence of other life.

2) The question is a valid one I believe because often the 4 forces are connected with life in terms of "fine tuning".

My view is that life is rather an unlikely development but which might take forms which have no relationship to the common features of life on Earth.

What is required for life is the achievement of several functions.

• Preserving its own structure
• Consuming resources for self maintenance, growth and reproduction
• Reproduction
• Adaptation

Life on Earth has achieved this through a wonderful system of chemical machinery at the core of which is a system which stores a description of proteins and manufactures them. The essential part of this is a codified form of all the information needed to create an organism including the "machine code" that defines how it operates at the lowest level. That this has been achieved using DNA, RNA and amino acids joined into proteins seems like just one way. I predict that within one hundred years, we will be able to create something which achieves all of the essential functions of life using another mechanism.

Not dwelling on the implementation, there are some more general things which have made the development of life possible. The first is a environment which has not become too extreme over a long period of time. If the Earth became very hot even very occasionally, the information stored in life would be wiped out. If very radical changes occurred suddenly, it is likely that all life would be wiped out because it would be badly adapted. It appears that all environmental crises during the fossil record have been less severe that this, doing no worse than wiping out 90% of species.

So as I see it, the prerequisites of life are the spontaneous generation of a chemical machine that allows the random encoding of structural information, the random development of some examples of such encoded structures that interact with their environment in a way which allows them to reproduce, a mechanism for randomly changing the information encoded which will occasionally be beneficial and an environment that never becomes either too severe for such structures to exist or changes too rapidly for some species to adapt and survive.

No, I don't think this has much to do with the specific laws of physics, and not the weak nuclear force, although I don't preclude the possibility that there might be universes with other laws in which life would never develop.

I infer that advanced life is really rather unlikely because here we are on the only planet we know it exists (and whose existence is a rather obvious prerequisite for us to be discussing it) but we know that it has taken 4.7 billion years, about 1/3 of the life of the universe so far. It is fairly safe to say that on planets chosen randomly, it is not unlikely that advanced life (or maybe even life) will not develop in a similar timescale. It may be very unlikely, or it may be quite likely, but our very limited information says that you can have a planet with suitable conditions and be waiting a very long time for anything other than primitive life, and probably quite a long time before even primitive life.

This is my point though. It seems to be the case that advanced life can indeed evolve without the weak force. Furthermore, if more than one fundamental constants are tweaked at once life can still be supportable.

I just got my new Scientific American as well, so I think I know where you are coming from.  

If your question is "why does OUR universe have the weak force" based on the anthropic principle my answer would be that the "weakless" multiverse in the article is really NOT OUR universe or anything close to it.

in "Looking for LIfe in the Multiverse" Jenkins and Perez speculate about dim "weakless" stars that shine by deuterium fusion.  However that process is not possible in our universe (minus the weak force), because there isn't enough deuterium left over from the Big Bang.    In a weakless universe, you can't manufacture neutrons from protons, so you are basically stuck with the ones you started with after the Big Bang.

So the weakless star scenario has to posit the following,  

 "... our universe contains overwhelmingly more matter than antimatter, but a small adjustment to the parameter that controls this asymmetry is enough to ensure that the big bang nucleosynthesis would leave behind a substantial amount of deuterium nuclei."

This strikes me as pretty facile.  A "small adjustment to the parameter that controls the asymmetry of matter and anti-matter?"  At this point my guess is that the Law of Unintended Consequences would make any predictions about life in such a universe meaningless.

Perhaps there is SOME universe without the weak force that could have life, but not OURS.

It was interesting to note the authors' statement about the cosmological constant, but I found it disappointing to include the Weak Anthropic Principle occasionally.