The Multiverse and Anthropic Principle are not enough

The question: why are we all here? used to be the purview of religion. The Bible claims that God created the universe and human beings by His Word. The universe was literally spoken into existence.

Many creation stories, such as the one in the Book of Genesis, propose the universe was created ex nihilo or “out of nothing.” Others propose a primordial chaos that was shaped by a creator being or some “diver” creature building the lands out of primordial waters.

In the 20th century, physicists have taken over the role of high priests of creation. They now control the story of how the universe came into being. At first, they believed the universe was static and eternal. Then, Einstein’s theory showed that it must not be static but growing, implying it had a hot dense beginning. 

We infer this is true from numerous observations. What we don’t know is how the universe got to be the way it is.

This is called fine tuning.

Fine tuning is the idea that the physical constants of the universe appear to be finely tuned for the appearance of matter and therefore life.

A common objection to fine tuning is that, well no, life adapted to whatever was here. Life is finely tuned to the universe, not the other way around.

That is an ignorant statement at best. If there is no matter, then how can there be life? If, for example, the balance of mass and energy in the universe were not precise, the universe would simply have collapsed back in on itself. If other features like proton masses were different, we wouldn’t have elements. There would be no building blocks.

It is as if we came upon a world made of beings made of Lego. We inferred that world must be finely tuned for Lego life, and someone objected, saying, no, life simply adapted to the existence of Lego. The issue isn’t that the building blocks are Lego. The issue is that there are building blocks at all.

As King Lear said, “nothing will come of nothing.”

The universe is finely tuned to have elements that assemble into larger, more complex objects. That is required for life to exist. There are far more universes we can conceive of, using the constants of nature we know of, that contain literally nothing at all or nothing that can build on itself. Even the chance of stars existing is considered to be astronomically improbable.

Life requires complexity. It cannot exist within either a chaotic universe, where everything is moving too quickly and changing too fast for organization to build. Nor can it exist within an overly orderly universe where everything moves in smooth, periodic orbits and nothing unexpected ever happens.

Fine-tuning is a real problem.

One potential solution to fine-tuning is the anthropic principle. This principle states that the universe is finely tuned because we are here to observe it. If it weren’t so, then we wouldn’t be here and nobody could ask the question.

This is a neat but unsatisfying philosophical answer because it assumes the universe just appeared randomly with no explanation.

There are, in fact, a large number of possible universes in which human life could exist if produced randomly. The simplest of these is a Boltzmann Brain universe, attributed to Ludwig von Boltzmann, one of the fathers of statistical mechanics. In this universe, we are simply brains containing fake knowledge about the universe. We think we are here in some corporeal form for some duration of time when, in fact, we just got here, we are leaving in the wink of an eye, and all this is an illusion. We can’t disprove that we are in a Boltzmann Brain universe because our knowledge is fake. We have no information to go on.

A similar, more modern version of this argument is the simulation universe. In this case, as philosopher Nick Bostrom has argued, we are living in a simulation created by our descendants or maybe some other alien species, living in another universe, perhaps the “real” one or maybe another simulation. 

Bostrom has used Bayesian reasoning, meaning probability based on beliefs rather than measurements, to argue that we are more likely to be living in a simulation than a real universe. He reasons that it is far easier to simulate a universe than to make a real universe; therefore, there must be more simulations than real ones. Ergo, we are in one. This a nice bit of reasoning but based on a string of unsupportable, and hardly self-evident, premises.

Unlike the Boltzmann universe, we would be living in this Matrix and so have knowledge about the simulation, but like the Boltzmann universe, our knowledge is fake as it pertains to the real universe.

The simulation hypothesis does not directly solve the fine-tuning problem because it presumes there must be a real universe “somewhere.” That universe must be finely tuned for all these simulations to exist unless the universe simulation is itself a collective Boltzmann Brain.

If the simulation is perfect, in that we cannot tell that we are in a simulation in any way, then we reach a dead end in our questioning of reality. We have no access to it. If the simulation is imperfect, then there is hope we can determine that we are, indeed, in one. Are there glitches in the Matrix? Perhaps, but we haven’t detected any that cannot be explained as natural occurrences.

Philosophically, we can dismiss these two ideas, Boltzmann Brains and the perfect simulation hypothesis, on the basis that they call into question all the knowledge we have about reality. Thus, we can go no further with them as bases for understanding the world. We have to believe that we have at least some access to reality in order to make progress. It is, therefore, a practical requirement that we be living in a real universe or have access to it.

A viable and popular explanation of fine-tuning is the Eternal Inflation Multiverse theory. In this theory, our universe is one of many, many bubbles within a vast multiverse. Each universe appears within the multiverse as a false vacuum. 

A false vacuum is what allows matter and energy to exist. In a true vacuum, nothing can exist. Therefore, a false vacuum is genuine creation ex nihilo.

Each universe in the multiverse starts with a different set of constants. Therefore, each bubble is like a little planet. The analogy is a powerful one. Most planets in the universe are lifeless because they do not have the correct conditions for life. Because there are so many planets in the universe, however, there must be a certain percentage that do have those conditions by pure probability.

Universes work the same way. There are a vast number of them within the multiverse and most of them are lifeless. In fact, the vast majority of them do not even get started. In the same way that the universe is full of a lot of dust and clumps of matter that are not part of a planet or a star, the multiverse is full of a lot of failed false vacuum bubbles that collapse in on themselves or tear themselves to pieces. Only a few of the universes that start continue to grow and become full-fledged universes.

Of those universes, only a few have the right conditions for matter to exist.

And of those universes, only a few can produce matter of sufficient complexity that it can build, by the process of evolution, into life forms.

Thus, as the Earth is a rarity within the universe, so the universe is a rarity within a greater multiverse.

This is a neat idea, but it suffers from a number of problems, some have to do with the details of the theory; others are philosophical objections. This Quanta article has a deeper discussion of these issues.

One issue with the theory is that it depends on the multiverse sharing time across universes. Things are happening across the multiverse at the same time. How you measure time determines how universes appear and how likely they are. 

One way to establish a universal clock is to have an Immortal Watcher who is seeing all the universes appear and collapse. This Being can then observe the frequency of events and define probabilities. 

First, we sought to replace God with a Multiverse and now we find we need God again, not to create now but only to watch! It’s Deism all over again!

Still, there are real problems with this view of reality. Arbitrary choices about this multiverse predict arbitrary things which is a problem with any theory with no data.

It is as if we all lived underground our whole lives or at the bottom of the ocean and tried to infer what the universe outside of Earth was like that explained our existence. How could we imagine celestial objects like stars and planets, nebulae and cosmic microwave background radiation, gamma rays and quasars? It seems completely useless to go down the path of trying to define a multiverse we cannot measure.

Much like our ancestors when they developed their creation myths, all we have to go on are analogies. That ours are couched in advanced mathematics makes them no less arbitrary.

Unless we can see these other universes, perhaps by observing the collision of two “bubble” universes, creating them in a particle accelerator, jumping into a black hole and ending up in a new universe (good luck surviving), or traveling through a wormhole to another one, we have no hope of understanding what is really beyond the universe.

In fact, many theologians consider fine-tuning to be a good argument for the existence of a Designer. If anything it is as good an explanation as a Multiverse or any other physical theory that has no independent evidence.

Still, I suggest that if we are looking for fine-tuning arguments, we ought to look at fine-tuning that makes our universe the most likely to occur. If our universe was made to produce life, it certainly doesn’t appear that way.

If the universe is finely tuned, why is it not full of life? Why is the vast majority of the universe lifeless?

One potential explanation is that the universe is not finely tuned for life, but rather life is a byproduct of whatever the universe is finely tuned for. Lee Smolin suggests that the universe is naturally selected to produce black holes, which may be the “eggs” from which new universes hatch. It is possible to show how a black hole singularity may produce a Big Bang singularity in another universe using standard General Relativity, so this isn’t pure fantasy. This is part of Cosmological Natural Selection (CNS) theory.

Even if this is not quite true, we do know that our universe is unique. It is unique in that it neither expands too quickly nor too slowly. It produces matter and clumps together and is stable for long periods of time, long enough to produce complex objects. That longevity and the ability for matter to exist and be stable are not likely with just a random choice of fine-tuning parameters.

The universe has a kind of internal complexity apart from life that is unlikely to be the product of random chance nor merely the product of the anthropic principle. And you might wonder, if we could observe it long enough and speed up what we see so that we could see it all unfold over billions of years, we might even start to believe the universe itself is alive: finely tuned by the same processes that allowed life on Earth to exist.