Astronomy & Cosmology
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Alternative Universes
Introduction
The Inflationary Big Bang is the most widely accepted theory for the formation of the Universe. This does not mean it is accepted universally! There are a number of scientists, of varying caliber, who do not feel the Big Bang has all the answers, and have proposed alternatives. Many of the alternatives have more issues than the Big Bang, so are not included here. I believe that, though there may well be corrections to it over time, the Big Bang cosmology is essentially correct. Critics have identified a number of issues with the theory, though most are explained by dark matter or inflation scenarios. Some criticisms are based on older data, like the age of the Universe being less than the age of some of the older globular clusters, where recent data have shown this not to be the case.
Some of the examples we address here are fairly controversial physics, based on the idea of "multiple universes" or Multiverse theory. This is not a reference to Michael Moorcock's literary Multiverse! Sir Martin Rees, the British Astronomer Royal at the time, said in 1998 that "This new concept is, potentially, as drastic an enlargement of our cosmic perspective as the shift from pre-Copernican ideas to the realization that the Earth is orbiting a typical star on the edge of the Milky Way."
Many scientists are concerned that the Universe we inhabit is so finely tuned to us. Some have embraced the anthropic principal, but to many, myself included, the Weak Anthropic Principal is too wishy-washy, while the Strong Anthropic Principal is too close to intelligent design. The idea of a Multiverse, postulating a possibly infinite number of universes, or a universe that re-creates itself an infinite number of times, overcomes these difficulties with statistics. If there are an infinite number of universes, it is no surprise that we inhabit one that is suitable for our type of life. Of course, what we discuss here is tied up intimately with the origins of the Universe, as described in the sections on the Early Universe and Alternatives to the Big Bang.
In this section, I discuss some of the various theories and the scientists behind them. I have tended to concentrate on the ideas that I find most interesting or most appealing, so some proposals, like Max Tegmark's Mathematical Universe Hypothesis, also known as the Ultimate Ensemble, have been left out. Some theories, the Chaotic Inflation postulate, for example, have become mainstream. I hope you find these interesting, and do remember that all the ideas in this section have a mathematical formulation to back them up. While only one of them, at the most, could be correct, they are all (theoretically) feasible.
Most, but not all, of the cyclic universe alternatives do not stand up to scrutiny because of conflicts with the second law of thermodynamics; with a couple of exceptions, I have excluded these, for now.
A recent (July 2010) suggestion from Wun-Yi Shu of the National Tsing Hua University in Taiwan seems to have had a great deal of publicity. It proposes re-writing General Relativity and allowing the gravitational "constant" and the speed of light to vary over cosmological time. He suggests that, as the Universe evolves, time & space are interchangeable, with the (varying) speed of light as the conversion factor, and that mass & length are interchangeable, with the conversion factor as a function of the (varying) gravitational “constant” and the speed of light as: G/c2. There is an excellent refutation by S.C. Kavassalis at Bad Physics.
Some of the examples we address here are fairly controversial physics, based on the idea of "multiple universes" or Multiverse theory. This is not a reference to Michael Moorcock's literary Multiverse! Sir Martin Rees, the British Astronomer Royal at the time, said in 1998 that "This new concept is, potentially, as drastic an enlargement of our cosmic perspective as the shift from pre-Copernican ideas to the realization that the Earth is orbiting a typical star on the edge of the Milky Way."
Many scientists are concerned that the Universe we inhabit is so finely tuned to us. Some have embraced the anthropic principal, but to many, myself included, the Weak Anthropic Principal is too wishy-washy, while the Strong Anthropic Principal is too close to intelligent design. The idea of a Multiverse, postulating a possibly infinite number of universes, or a universe that re-creates itself an infinite number of times, overcomes these difficulties with statistics. If there are an infinite number of universes, it is no surprise that we inhabit one that is suitable for our type of life. Of course, what we discuss here is tied up intimately with the origins of the Universe, as described in the sections on the Early Universe and Alternatives to the Big Bang.
In this section, I discuss some of the various theories and the scientists behind them. I have tended to concentrate on the ideas that I find most interesting or most appealing, so some proposals, like Max Tegmark's Mathematical Universe Hypothesis, also known as the Ultimate Ensemble, have been left out. Some theories, the Chaotic Inflation postulate, for example, have become mainstream. I hope you find these interesting, and do remember that all the ideas in this section have a mathematical formulation to back them up. While only one of them, at the most, could be correct, they are all (theoretically) feasible.
Most, but not all, of the cyclic universe alternatives do not stand up to scrutiny because of conflicts with the second law of thermodynamics; with a couple of exceptions, I have excluded these, for now.
A recent (July 2010) suggestion from Wun-Yi Shu of the National Tsing Hua University in Taiwan seems to have had a great deal of publicity. It proposes re-writing General Relativity and allowing the gravitational "constant" and the speed of light to vary over cosmological time. He suggests that, as the Universe evolves, time & space are interchangeable, with the (varying) speed of light as the conversion factor, and that mass & length are interchangeable, with the conversion factor as a function of the (varying) gravitational “constant” and the speed of light as: G/c2. There is an excellent refutation by S.C. Kavassalis at Bad Physics.
| There is a useful overview of Multiverse theory on the Pomona College web site. |
| There is a really good BBC interview with Michio Kaku. |
| An interesting selection of articles from Andrei Linde at Stanford University. |