Some facts and tidbits about the Universe. (From the May 2007 issue of Astronomy.)

• – The Universe is 13.7 billion years old.
• – The “observable Universe” is 93 billion light-years across.
• – The average temperature of the cosmic microwave background is 2.725 degrees Kelvin.
• – 74 percent of all matter and energy in the Universe is “Dark Energy”.
• – 22 percent is “Dark Matter”.
• – 4 percent is ordinary matter – humans, planets, stars, etc.

The article continues, drawing distinctions around what an “expanding universe” is, and how the Big Bang wasn’t any kind of explosion, but rather involved a very rapid and extreme expansion of space itself. These are all areas that students find conceptually difficult to understand. For example, students need to understand that there is no “center” to the Universe. Wherever you are, all of the rest of the Universe appears to be rushing away from you (outside of local clusters of galaxies).

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