Calculations of the age of the universe vary wildly. However, they seem to stay within a range of 10-18 billion years. There are a bunch of ways to calculate the age of the universe. I am currently not sure of the values given by these experiments, so I have none. Here are some:
  • Expansion of universe
    Measure the hubble constant. This is the rate at which the universe is expanding, and it can be measured by finding out relative velocities of other stars and doing some weird math things to those numbers. With that rate, use some weird physics things to simulate that rate going backwards, until you hit the big bang.
  • Age of atomic nuclei
    Look at the concentrations of various isotopes in rocks. Use radiological dating to see how old your object is. The universe is at least that old. Also, if you find extremely low quantities of a given isotope, assuming that some of it originally existed, you can use the half-life to get another minimum age.
  • Age of oldest stars
    Take the oldest white dwarf star you can find (date it radiologically). The star was formed after the universe begun, and therefore the universe is at least as old as that star.
New(ish) news: The WMAP satellite has allowed us to measure the age of the universe to an unparalleled precision: +/- 1%. The answer is 13.7 billion years. This was accomplished by examining the detail in the structure of the microwave background radiation. To me, this seems rather young, as the earth is 4.5 billion years old.

I was thinking about this recently. I'm a creationist (ducks to avoid the bottles and tomatoes flying through the air), and as such, am often considering the fundamentalist "thousands of years old" vs the contemporary "billions of years old" view.

When applied to the Universe, unless we have our distances wrong by a very large factor indeed, there are four explanations to what we see:

What's the problem with it simply being created a few thousand years ago? Simply this: most objects we have observed are more than "thousands" of light years away, so the light from them would not yet have reached us. If the Universe were created and left to propagate its own light, it would take about 100,000 years before we'd even see the full Milky Way. Most of the sky would be black, and every so often, a new star would pop into view. We certainly wouldn't have any pictures of other galaxies.

A few people have suggested that the speed of light could have changed over the years. However, the factor of change required combined with the intrinsic link between mass and energy (E=mc^2) does not give me any confidence in the suggestion (although see http://www.channel4.com/equinox/ein_transcript.html - thanks wertperch).

So we have two theories: that the Universe is indeed billions of years old; or that it is younger, and created with the light already in motion, giving the appearance of age.

This is going on my list of questions to ask when I enter into glory; it certainly isn't going to dent my faith down here!

Genesis 1
  1. In the beginning God created the heavens and the earth.
  2. Now the earth was formless and empty, darkness was over the surface of the deep, and the Spirit of God was hovering over the waters.
  3. And God said, "Let there be light," and there was light.
  4. God saw that the light was good, and he separated the light from the darkness.

The alternative vision on this is that the universe has no age (since the universe did not have a begin), and the estimation of 13.7 billion years is a relative age (dating back to the most ancient event we can measure), by which it is expressed that the universe is endless in time.

(And as an explenation to this, it is to be stated that matter/energy can only be converted/transformed, but not created or destroyed, and the reasoning that time can not be said to have begun, since a beginning of any something must itself be positioned within time itself to denote something meaningfull, thereby classifying events that happen "out-side" of time as not meaningfull and not physical notions).

Note also that the Big Bang theory as a scientific theory does not prescribe that the universe began with the big bang, and that the big bang event is not the begin of time. All theories about what caused the big bang, are not strictly part of the big bang theory itself, but merely extentions to that, like the theory of cosmic inflation,or the ekpyrotic model of string theory.

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