Multiple Universes & Anthropic Principle, Lead: Rachel Whitaker

3/1/2004

Summary by Nancy Brady Littlefield:

Multiple Universes & Anthropic Principle

Rachel presented an overview of the Big Bang theory and how it has led to questions about why our universe took the precise form it did. For example, why did such an incredibly dense piece of matter explode into the forms of galaxies and stars, making such a “lumpy” universe? The precision seems at once too diverse and too precise. Questions like this led to the “Inflationary Universe” theory (propounded among others by Andrei Linde) which suggests that our universe can “spark” other universes, and that black holes, containing vast amounts of dense matter, are where these other universes can be created. This theory makes the claim that universal physical laws as we know them, can become “scrambled”, leading to variations of the laws and variation of life. It still leaves room for the Big Bang, which is inflationary by its very nature.

A DVD of the program “The Elegant Universe” was shown, which discussed the various “multiple universes” theories, including the Anthropic Principle, which states that humankind can still be an important part of the Universe’s life, and that the Universe as we know it must be structured so as to be hospitable for life—otherwise we could not exist to know it. But because we only have this one universe to perceive, it can only be from a limited set of observations that we can try for conclusions. There are three forms of this Anthropic Principle: weak, strong and final. The weak form argues that, as long as life is not impossible, then no supernatural force is needed to put it into existence. The strong form states that observed universes must have those properties that can produce life, and the final form claims that to exist at all, the universes require the existence of life (i.e., of observers). But what are we comparing our universe to? Examples of Fundamental Constants that had to be finely tuned: the four forces of electromagnetism, gravitational constant, the weak nuclear force and the strong nuclear force. If the ratios between these forces change, everything is changed. The ratios are the important crux. This led to discussion of the forces and their relative relationships. It was said that no evidence exists that the relationship between forces could be anything else, but is this relationship fixed? There is a relationship amongst the forces, but unification of the forces was only at the time of the Big Bang.

One can construct physical laws as a starting point, but would this mean that alternate universes, or permutations of our universe, must be infinite? We could only imagine the possibility that the forces could be changed, not see for ourselves. We can only see one universe—ours. One could assume that in a process of natural selection, some universes that could “propagate”, have propagated, that there were universe “families” and “types” with differences one to the other.

Then Rachel discussed the importance of String Theory in all of this: that beyond atoms, quarks and other subatomic particles, there are “little strands of vibrating energy”; these can exist in ten different dimensions. But there were five separate string theories, and ten dimensions were not enough to unify them. So the M Theory stated there were at least eleven dimensions, allowing the string to “stretch”, to envelop universes by encapsulating membranes, each having different dimensions. At the very beginning of the universe, when forces are combined, all the four forces were united as one—almost a monistic (or even monotheistic?) theory. String theory seems to allow for this, and it naturally can predict, or allow for the possibility of, multiple universes.

It has been theorized that the string membrane, or “brane” could grow to universe-size, and that our universe may be only one of many. In “The Elegant Universe” a sliced bread motif was used, comparing our universal experience to but one slice. This view may solve the “gravity problem”, although gravity is weak and we overcome it all the time. The electromagnetic force is much stronger than gravity, or so it appears; however, gravity may just appear to be weak. A pool table was used as an example. As the pool balls are knocked against the sides of the table, the object is stopped but the sound waves continue off the surface into the surrounding area. So…perhaps gravity waves are like sound waves. Gravitons can thus possibly escape to other “membranes”, thus making gravity appear to be a weak force in our universe. Could we possible “feel” the gravitational perturbations of other “life” in other universes?

Of course, this all simply raises more questions. Are there any hypotheses that are test-able? Is “dark energy” the energy that is leaking in from other universes? An example used was of a balloon: there is no edge on the surface of a balloon and inhabitants of a two-dimensional world cannot accurately or even conceivably perceive a third. How can there be an interface between “us” and “them”? Could the interface be through the mind? Through dreams? Through creativity? Could the “strings” of string theory create another Big Bang? Would mathematics change in another universe, or dimension? (When the ratios between the four forces change.) It was pointed out that by definition, mathematics does NOT change, that math truths are something we discovered. We did not create those laws. Mathematic concepts do not need experiments. We apply math to our world; it is not an abstraction from data.

If there are many universes nearby, could we figure out gravitational signals encoded through math? Could we use gravitons to send a pattern? It would have to be modulated. If we received a response, would we recognize it? Further discussion explored all these questions, and although no firm conclusions were reached, our thoughts and minds were stimulated.