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I read one reason given for the Big Bang's beginning of the universe is that stars are not old enough to have produced the large amounts of helium present today. Wouldn't this actually be a reason to believe that the universe is more than the 13.7 billion years old than the Big Bang theory says it is?
- Edward J. Doscher (age 84)
Toms River, NJ USA
If you take just one fact, like the concentration of helium, and search for explanations of it, then you do have a lot of choices. However, if you try to explain a lot of facts with a consistent story then the choices are much more limited. In this case, there are other concentrations- hydrogen, deuterium, helium 3, and lithium- which also have to be explained. It turns out that the whole collection fits with the idea there was a big bang and the light elements were formed as it cooled. The time that has elapsed since the BB is calculated in several ways, which all give consistent answers of 13.7 billion years. The simplest way is to measure how fast distant galaxies are moving away from us (via the red shift), compare with the distance to them (estimated from brightness of certain stars) and figure out how long ago everything was back near here by dividing distance by speed.
There are some small corrections to this procedure, but maybe that's a good enough description for starters.
(published on 05/26/08)
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