Posted: Sep 26, 2011 6:24 pm
twistor59 wrote:I was just thinking - sometimes questions keep coming up repeatedly, for example:
"How come we can observe galaxies receding from us faster than light?"
"What is the evidence that our universe is (or is not) fine tuned for life ?"
I keep my own FAQ files. Answers to these 2 questions are in it.
For the first, the answer is in the following article:
8. Lineweaver CH and Davis TM Misconceptions about the Big Bang, Scientific American 36-45 March 2005. http://www.sciam.com/article.cfm?chanID ... 414B7F0147
For the second:
"According to the Anthropic Principle, we are entitled to infer facts about the universe and its laws from the undisputed fact that we (we anthropoi, human beings) are here to do the inferring and observing. The Anthropic Principle comes in several flavors.
In the "weak form" it is a sound, harmless, and on occasion useful application of elementary logic: if x is a necessary condition for the existence of y, and y exists, then x exists. If consciousness depends on complex physical structures, and complex physical structures depend on large molecules composed of elements heavier than hydrogen and helium, then, since we are conscious, the world must contain such elements.
"But notice that there is a loose cannon on the deck in the previous sentence: the wandering "must". I have followed the common practice in English of couching a claim of necessity in a technically incorrect way. As any student in logic class soon learns, what I really should have written is: It must be the case that: if consciousness depends ... then, since we are conscious, the world contains such elements.
The conclusion that can be validly drawn is only that the world does contain such elements, not that it had to contain such elements. It has to contain such elements for us to exist, we may grant, but it might not have contained such elements, and if that had been the case, we wouldn't be here to be dismayed. It's as simple as that.
Take a simpler example. Suppose John is a bachelor. Then he must be single, right? (That's a truth of logic.) Poor John -- he can never get married! The fallacy is obvious in this example, and it is worth keeping it in the back of your mind as a template to compare other arguments with."
Daniel Dennett, Darwin's Dangerous Ideas, pp. 165-166.