Monday, June 22, 2009

Uncommon Descent Contest 4: Can we save physics by dumping the Copernican principle? - Winner announced

The question is here. It looks at “Does Dark Energy Really Exist? Or does Earth occupy a very unusual place in the universe?” by physicist Timothy Clifton and astrophysicist Pedro G. Ferreira, who argue just that: If we give up the Copernican principle, we do not need dark energy to explain the composition of the universe.(Scientific American, March 23, 2009)

The winning entry is by KeithDP:

I liked it because he made a number of pertinent points that less often raised than they should be:

- "The problem with the principle is how do you define special?" The fact that Earth is the only known home of life should cause it to be classified as special, at least for now.

- "Unlike the multiverse, the theory [re the existence or necessity of dark energy] is testable and efforts are underway to confirm or dismiss it." Indeed. Consider the upcoming SNO+ experiment in Sudbury, Canada, whose awesome facilities I toured recently - which aims to trap a particle of dark matter. That would be a good beginning.

- " ... will we also discover that Earth’s place in the centre of a vast cosmic void is another necessary precondition for life?" That too would be useful, because we could revise current estimates of where to look for life. Too many estimates have been Drake equation-style "choose your own parameters." Fun, sure, but science fiction.

So KeithDP needs to provide me with a current postal address at to receive his free copy of the Privileged Planet DVD.

I will shortly judge Question 5: Darwinian fairy tales: Why middle-aged men have shiny scalps: "What is the down side for serious Darwinists to just cutting the “evolutionary psychology” psychodrama loose, and focusing on what real science can say about evolution?"

Now here is KeithDP's entry:

Copernicus’ modest proposition was that the solar system is heliocentric and not geocentric. Centuries later came the Copernican principle: the idea that Earth does not occupy any special position in the universe. In the last few decades this principle has been expanded to include the idea that there is nothing special about humans or the Earth. This idea is often called the Copernican principle of mediocrity. In recent years some astronomers have taken the idea further still and have popularized the notion that there is nothing special about our universe, as it is just one among an infinite number of other universes: a multiverse. Although no evidence supports the theory, and as it is not testable no evidence is ever likely to, it is considered the natural and ultimate culmination of the Copernican principle.

The problem with the principle is how do you define special? In the Rare Earth hypothesis, scientists Ward and Brownlee identify no less than a dozen factors that make complex life possible on Earth. In their view these factors make the Earth, if not special, than certainly very rare. Astronomer Guillermo Gonzalez goes further and identifies factors that make the Earth particularly suitable for scientific discovery. In his view the Earth is more than a rare planet; it is a privileged one. Recently some astronomers have questioned the standard model of the universe that holds that at least 70% of the universe is composed of mystery material. They propose this material is unnecessary if we ignore the Copernican principle and assume instead that the Earth lies at or near the centre of a vast cosmic void with far lower density than other regions of space.

Unlike the multiverse, the theory is testable and efforts are underway to confirm or dismiss it. Considering what we have learned about what makes the Earth’s particular location in the solar system and in the galaxy especially suitable for life, will we also discover that Earth’s place in the centre of a vast cosmic void is another necessary precondition for life?

Do we have further need of the Copernican principle? Or is it instead merely a personal philosophical position about humanity’s place? Does it tell us more about the belief system of those who hold it than it does about the universe?