• Question: Are there important aspects of the Universe that can only be understood using the Anthropic Principle? Or is this principle unnecessary, or perhaps inherently unscientific?

    Asked by maxsmith1 to Arttu, Ceri, James_M, Monica, Philip on 13 Jun 2011.
    • Photo: Arttu Rajantie

      Arttu Rajantie answered on 13 Jun 2011:

      I fear the answer is yes, there are important aspects of the universe that can only be understood using the anthropic principle, and yes, in a sense it is inherently unscientific.

      The anthropic principle means the (rather obvious) point that the universe has to be such that we can exist, because otherwise we would not be here observing it.

      There are some questions in science for which the anthropic principle gives a satisfactory explanation. For instance, it explains why conditions on Earth (temperature, composition of the atmosphere etc.) are pretty much ideal for life, at least as we know it. The reason is simply that there are huge numbers of planets in the universe, but life could only develop on the ones where the conditions allowed it, and therefore we must necessarily live on one of those.

      One can use the same argument for the whole universe. For example, a completely empty universe would be theoretically possible but we obviously cannot be living in one. This is perfectly logical, but it does not actually give any useful information about why the universe is not empty, i.e., where all the matter came from.

      Therefore I would say that the principle allows us to understand, but not really explain, certain things about the universe.

    • Photo: James M Monk

      James M Monk answered on 13 Jun 2011:

      I find the anthropic principle fairly unsatisfying. It makes sense, but I’m not sure it really tells us anything. For it to work there must be more than one Universe, or at least disconnected regions of the Universe with different conditions. As far as I know there is no evidence for such multiple universes, nor even a way we could obtain evidence since by definition they would have to be completely disconnected from our own.

      To some extent I think it comes down to how much you are prepared to believe in mathematics as a self consistent system that not only describes the Universe but *is* the Universe. Are you prepared to believe, based on nothing but the fact that a Universe independent of our own *could* exist that it does exist and therefore motivates the use of the anthropic principle.

      I suspect that has very little to do with science.

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