|Speaker:||Mario Livio, Space Telescope Science Institute|
|Topic:||“The Beauty of the Cosmos and the Accelerating Universe”|
President Collins called the 2146th meeting of the Philosophical Society of Washington to order at 8:20 p.m. on April 26, 2002. The Recording Secretary read the minutes of the 2145th meeting and they were approved.
The speaker for the 2146th meeting was Mario Livio of the Space Telescope Institute. The title of his presentation was, “The Beauty of the Cosmos and the Accelerating Universe.”
Mr. Livio addressed these two related issues as: “Is our universe truly accelerating?” and, “How do you define ‘beauty’ in a physical theory?”
On the topic of an accelerating universe, Mr. Livio described how in 1998, two groups of astronomers presented evidence that the expansion of our universe is accelerating. This is scientifically shocking—this is magic! It has long been recognized that the universe is expanding. Edwin Hubbell discovered in the 1920's that all distant galaxies recede from us and the speed of recession is proportional to the distance away. Now if gravity were the only force acting to alter the expansion rate, then it would be expected that the universe would be decelerating, or in the case of a universe with essentially zero mass, it would be expanding at a constant rate. However, results of recent observational cosmology provide evidence that the universe's expansion is neither slowing down nor remaining steady, but is actually accelerating. Expansion of the universe is speeding up.
The initial evidence for this acceleration came from a particular type of supernova explosion that in specific cases reaches a uniform luminosity. Observations show the most distant of this type of supernova are 20 percent fainter than those nearby. This observation is easily explained if the universe expansion is accelerating—our motion away from the distant supernovae has speeded up since the light left them, sweeping us farther away than we otherwise would be in a universe with a constant or a decelerating rate of expansion.
Other explanations for the faintness of these distant, exploding supernovae, such as intervening dust would also dim the light. However, no observational support has been found for such alternative explanations.
On the subject of beauty in a physical theory, Mr. Livio stated the question involves the quality that makes an object seem pleasing or satisfying in a certain way. Mr. Livio defined beauty in theory as incorporating symmetry, simplicity, and adherence to the Copernican principle that we do not occupy a privileged place in the universe. For example, consider the beauty inherent in the symmetries and simplicities in Vermeer's painting, “Girl with a Pearl Earring.” Similarly, examine the quality of beauty that we behold in photo images of the stellar Eagle Nebula. As with the Vermeer painting, part of the beauty in the Eagle Nebulae lies in the symmetries of its configuration. Mr. Livio also described symmetries in the Laws of Physics where symmetry is related to something that does not change. For example, the Laws of Conservation of Linear Momentum and Conservation of Angular Momentum work on the Moon as well as they do on the Earth. Another example of the beauty of symmetry the speaker demonstrated used a balloon with the balloon's surface representing the universe and lots of little galaxies painted onto it. As the balloon is blown up and expanded, all the painted galaxies recede from each other. There are no edges, there is no center, and all the galaxies remain on the surface. An analogy could be made to the place settings on a round dinner table which have no left or right orientation until somebody claims a bread and butter plate which breaks the symmetry and an aspect of beauty of the original table arrangement.
Another aspect of beauty is associated with simplicity, or “less” is more beautiful than “more.” Alternately, we could move from many questions to one question, or from many laws to one fundamental law. In the beginning when the universe was very hot, there was only one fundamental force. As the universe expanded and cooled, gravity split off and broke the simplicity and the initial beauty of the one simple fundamental force. As we know, there are now four fundamental forces: gravity, electromagnetic, the strong nuclear force and the weak nuclear force.
Mr. Livio then closed his presentation and kindly answered questions from the floor. President Collins thereupon thanked Mr. Livio for the Society, welcomed him to membership, announced the next meeting and made the usual parking announcement. He then adjourned the 2146th meeting to the Social Hour at 9:32 p.m.
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