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Our future, our universe, and other weighty topics


Tuesday, May 19, 2015

Stubbornly Denying the Evidence For Cosmic Fitness

Recently I read two books that touched upon the issue of cosmic fine-tuning, a question that I have often written about on this blog. One excellent book is the rather poorly titled book “Modern Physics and Ancient Faith” by Stephen M. Barr, a physics professor at the University of Delaware (which doesn't at all brush away religious thinking as an ancient relic, despite the title). In that book there is an interesting discussion of “anthropic coincidences” that are necessary for our existence. One example given is that of a parameter called v. On pages 126-127 the book makes these interesting comments:

The long technical name of the parameter v is “the vacuum expectation value of the Higgs field.”....The value of v is a great puzzle to particle theorists; in fact, it is one of the central puzzles of physics. What is puzzling is that in reasonably simple theories v seems to want to come out to be, not 1, but a number like 1017, i.e, 100,000,000,000,000,000...As far as the possibility of life emerging in our universe is concerned, it would be a disaster for v to be 100,000,000,000,000,000. It would also be a disaster if it were 100,000,000,000,000, or if it were 100,000,000, or if it were 100,000, or if it were 100. Indeed, it would be a disaster if it were 10, or 5, or even 1.5. It would probably be a disaster if v were even slightly different from the value it happens to have in the real world.

So nature “hit the bullseye,” a very distant bullseye, it would seem. This is only one of many astonishing “coincidences” required for our existence. Barr lists seven other such cases, one of which is even more dramatic: the fine-tuning of the cosmological constant. As Barr puts it on page 130 of his book:

In order for life to be possible, then, it appears that the cosmological constant, whether it is positive or negative, must be extremely close to zero – in fact, it must be zero to at least 120 decimal places. This is one of the most precise fine-tunings in all of physics.

To their credit, modern cosmologists and physicists have been very open and candid about discussing such “coincidences.” I could easily fill up a longish blog post doing nothing but quoting all of the physicists and cosmologists who have remarked on how remarkably fit-for-life or seemingly fine-tuned our universe seems to be. But there is one exception. Physicist Marcelo Gleiser will have none of this thinking. On page 232 of his book A Tear at the Edge of Creation, Gleiser stubbornly says, “There is absolutely no evidence that our Universe is fit for life.”

If I didn't know that some physicists make enormously silly assertions about infinities of parallel universes, and ask you to believe there are an infinite number of copies of yourself, I might call the previous statement by Gleiser the silliest thing I have ever heard from a physicist. It's a statement that would only make sense if you were a robot scanning a biologically lifeless universe.

Glesier provides no real scientific statements or references to back up his weird claim that there "is absolutely no evidence that our Universe is fit for life.” He merely gives a little armchair reasoning that does not hold up to scrutiny. 

First, Gleiser attempts to persuade us that someone reasoning that the universe is fit for life is like someone coming into a library and concluding that all of the books were made for him, or that all of the books were made for English-speaking readers like himself. But this analogy isn't appropriate, and doesn't correspond to the type of reasoning made by those who point out the ways in which the universe is fine-tuned for life.

Let's imagine a scale of claims ranging from the very specific to the very general.
  1. Things are arranged in a way that benefits (or makes possible) me in particular.
  2. Things are arranged in a way that benefits (or makes possible) people who speak my language.
  3. Things are arranged in a way that benefits (or makes possible) humans in general.
  4. Things are arranged in a way that benefits (or makes possible) carbon-based life forms.
  5. Things are arranged in a way that benefits (or makes possible) some type of life, rather than preventing any type of life.
Gleiser is suggesting that those who say that the universe is remarkably fit for life are like people who make the first assertion, or possibly the second assertion. But they are not. Almost all claims of cosmic fitness or cosmic-fine tuning involve claims like the last of these claims, claims that are extremely general and cannot be attacked on a basis of assuming an intention too specific. So Gleiser's library analogy isn't fair, and doesn't back up his claim. It's particularly weak for Gleiser to be using a library analogy to try to back up a claim of cosmic non-fitness for life (as a library consists of manufactured objects that were designed for a specific purpose).

Gleiser then goes on to give this reasoning:

For a clever fish, water is “just right” for it to swim in. Had it been too cold, it would freeze; too hot, it would boil. Surely the water temperature had to be just right for the fish to exist. “I'm very important. My existence cannot be an accident,” the proud fish would conclude. Well, he is not important...The ocean temperature is not being controlled with the purpose of making it possible for life to exist.

This reasoning does nothing to establish Gleiser's strange claim that there “is absolutely no evidence that our Universe is fit for life.” In his fish analogy he is talking about a particular organism that is adapted to a particular local parameter (the water temperature); cold-water fish are adapted to cold water, and warm water fish are adapted to warm water. But none of the main “anthropic coincidences” mentioned in discussions of cosmic fitness involve merely local conveniences, nor do any of them involve things to which the human organism or earthly life has adapted itself to. Instead, they involve things that are prerequisites for any type of life at all – and most of them involve things that are prerequisites for any type of universe with stable solid matter and stable stars. So Gleiser's little fish analogy falls flat. Again, the analogy has no relevance to the typical discussions of physics and cosmic fitness.

Gleiser then gives this reasoning:

Think of the billions, probably trillions, of barren worlds in our galaxy alone. I can't read the message “just right” for life written in so many dead worlds.

This makes no sense at all. Since planets can have different distances from a star, there will inevitably be some planets that are barren because they are too cold or too hot. But the existence of such planets does nothing to discredit a claim of cosmic fitness for life, particularly since some of these “barren” planets (such as Jupiter) help indirectly to allow life to flourish (if Jupiter didn't exist, our planet would get hit by too many comets and asteroids, many of which are diverted by Jupiter's gravity). “Fitness for life” simply means having the characteristics that allow life to exist, not some much more extravagant claim such as “designed in a way that results in 100% of available planets bearing life.”

Finally, Gleiser lamely asks: “If the constants of nature are so fit for life, why is life so difficult to find?” The answer is: it isn't, and it's all around us. As for looking for extraterrestrial life, we've just begun to do that, and we still haven't spent the money needed to make a very serious effort in that regard (as spending on SETI has been “peanuts” compared to what was spent on big physics projects such as the Large Hadron Collider) .

Gleiser's reasoning on this topic is without merit, and I smell a very stubborn denialism in his claim that “there is absolutely no evidence that our Universe is fit for life.” Quite to the contrary, many modern physicists and cosmologists have admitted that there is abundant evidence that the universe is astonishingly fit for life.  Read here for more about this topic.

cosmic jackpot
Only some of the lucky "coincidences" needed for life's existence