I’ve been procrastinating over this topic for some time, probably a whole year, such is the epistemological depth hidden behind its title; plus it has religious as well as scientific overtones. So I recently re-read John D. Barrow’s The Constants of Nature with this specific topic in mind. I’ve only read 3 of Barrow’s books, though his bibliography is extensive, and the anthropic principle is never far from the surface of his writing.
To put it into context, Barrow co-wrote a book titled, The Anthropic Cosmological Principle, with Frank J. Tipler in 1986, that covers the subject in enormous depth, both technically and historically. But it’s a dense read and The Constants of Nature, written in 2002, is not only more accessible but possibly more germane because it delineates the role of constants, dimensions and time in making the universe ultimately livable. I discussed Barrow’s The Book of Universes in May 2011, which, amongst other things, explains why the universe has to be so large and so old if life is to exist at all. In March this year, I also discussed the role of ‘chaos’ in the evolution of the universe and life, which leads me (at least) to contend that the universe is purpose-built for life to emerge (but I’m getting ahead of myself).
We have the unique ability (amongst species on this planet) to not only contemplate the origins of our existence, but to ruminate on the origins of the universe itself. Therefore it’s both humbling, and more than a little disconcerting, to learn that the universe is possibly even more unique than we are. This, in effect, is the subject of Barrow’s book.
Towards the end of the 19th Century, an Irish physicist, George Johnstone, attempted to come up with a set of ‘units’ based on known physical constants like c (the speed of light), e (the charge on an electron) and G (Newton’s gravitational constant). At the start of the 20th Century, Max Planck did the same, adding h (Planck’s quantum constant) to the mix. The problem was that these constants either produced very large numbers or very small ones, but they pointed the way to understanding the universe in terms of ‘Nature’s constants’.
Around the same time, Einstein developed his theory of relativity, which was effectively an extension of the Copernican principle that no observer has a special frame of reference compared to anyone else. Specifically, the constant, c, is constant irrespective of an observer’s position or velocity. In correspondence with Ilse Rosenthal-Schneider (1891-1990), Einstein expressed a wish that there would be dimensionless constants that arose from theory. In other words, Einstein wanted to believe that nature’s constants were not only absolute but absolutely no other value. In his own words, he wanted to know if “God had any choice in making the world”. In some respects this sums up Barrow’s book, because nature’s constants do, to a great extent, determine whether the universe could be life-producing.
On page 167 of the paperback edition (Vintage Books), Barrow produces a graph that shows the narrow region allowed by the electromagnetic coupling constant, α, and the mass ratio of an electron to a proton, β, for a habitable universe with stars and self-reproducible molecules. Not surprisingly, our universe is effectively in the middle of the region. On page 168, he produces another graph of α against the strong coupling constant, αs, that allows the carbon atom to be stable. In this case, the region is extraordinarily small (in both graphs, the scales are logarithmic).
I was surprised to learn that Immanuel Kant was possibly the first to appreciate the relationship between Newton’s theory of gravity being an inverse square law and the 3 dimensions of space. He concluded that the universe was 3D because of the inverse square law, whereas, in fact, we would conclude the converse. Paul Ehrenfest (1890 – 1933), who was a friend of Einstein, extended Kant’s insight when he theorised that stable planetary orbits were only possible in 3 dimensions (refer my post, This is so COOL, May 2012). But Ehrenfest made another revelation when he realised that 3 dimensional waves were special. In even dimensions, different parts of a ‘wavy disturbance’ travel at different speeds, and, whilst waves in odd dimensions have disturbances all travelling at the same speed, they become increasingly distorted in dimensions other than 3. On page 222, Barrow produces another graph demonstrating that only a universe with 3 dimensions of space and one of time, can produce a universe that is neither unpredictable, unstable nor too simple.
But the most intriguing and informative chapter in his book concerns research performed by himself, John Webb, Mike Murphy, Victor Flambaum, Vladimir Dzuba, Chris Churchill, Michael Drinkwater, Jason Prochaska and Art Wolfe that the fine structure constant (α) may have been a different value in the far distant past by the miniscule amount of 0.5 x 10-5, which equates to 5 x 10-16 per year. Barrow speculates that there are fundamentally 3 ages to the universe, which he calls the radiation age, the cold dark matter age and the vacuum energy age or curvature age (being negative curvature) and we are at the start of the third age. He simplifies this as the radiation era, the dust era and the curvature era. He contends that the fine structure constant increased in the dust era but is constant in the curvature era. Likewise, he believes that the gravitational constant, G, has decreased in the dust era but remains constant in the curvature era. He contends: ‘The vacuum energy and the curvature are the brake-pads of the Universe that turn off variations in the constants of Nature.’
Towards the end of the book, he contemplates the idea of the multiverse, and unlike other discussions on the topic, points out how many variations one can have. Do you just have different constants or do you have different dimensions, of both space and/or time? If you have every possible universe then you can have an infinite number, which means that there are an infinite number of every universe, including ours. He made this point in The Book of Universes as well.
I’ve barely scratched the surface of Barrow’s book, which, over 300 pages, provides ample discussion on all of the above topics plus more. But I can’t leave the subject without providing a definition of both the weak anthropic principle and the strong anthropic principle as given by Brandon Carter.
The weak principle: ‘that what we can expect to observe must be restricted by the condition necessary for our presence as observers.’
The strong principle: ‘that the universe (and hence the fundamental parameters on which it depends) must be such as to admit the creation of observers with it at some stage.’
The weak principle is effectively a tautology: only a universe that could produce observers could actually be observed. The strong principle is a stronger contention and is an existential one. Note that the ‘observers’ need not be human, and, given the sheer expanse of the universe, it is plausible that other ‘intelligent’ life-forms could exist that could also comprehend the universe. Having said that, Tipler and Barrow, in The Anthropic Cosmological Principle, contended that the consensus amongst evolutionary biologists was that the evolution of human-like intelligent beings elsewhere in the universe was unlikely.
Whilst this was written in 1986, Nick Lane (first Provost Venture Research Fellow at University College London) has done research on the origin of life, (funded by Leverhulme Trust) and reported in New Scientist (23 June 2012, pp.33-37) that complex life was a ‘once in four billion years of evolution… freak accident’. Lane provides a compelling argument, based on evidence and the energy requirements for cellular life, that simple life is plausibly widespread in the universe but complex life (requiring mitochondria) ‘…seems to hinge on a single fluke event – the acquisition of one simple cell by another.’ As he points out: ‘All the complex life on Earth – animals, plants, fungi and so on – are eukaryotes, and they all evolved from the same ancestor.’
I’ve said before that the greatest mystery of the universe is that it created the means to understand itself. We just happen to be the means, and, yes, that makes us special, whether we like it or not. Another species could have evolved to the same degree and may do over many more billions of years and may have elsewhere in the universe, though Nick Lane’s research suggests that this is less likely than is widely believed.
The universe, and life on Earth, could have evolved differently as chaos theory tells us, so some other forms of intelligence could have evolved, and possibly have that we are unaware of. The Universe has provided a window for life, consciousness and intelligence to evolve, and we are the evidence. Everything else is speculation.