How Old is the Universe

by John Carl Villanueva on August 10, 2009

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Milky Way. Image Credit: Atlas of the Universe

For Big Bang advocates, the most updated answer to the question, “How old is the Universe?” is 13.7 billion years, with an uncertainty of only 1%.

Now, this question is not only a thought-provoking one. If you were to direct it to an advocate of cyclical or oscillatory models of the universe, the query wouldn’t make sense at all. Hence, when you ask this question, I would have to assume that you are a believer of the one-beginning-one-end version of the cosmological model known as the Big Bang.

Cyclical or oscillatory models, although also offshoots of the Big Bang, are never ending. In these models, you have a sequence of infinite pairs of Big Bangs and Big Crunches (each pair known as a Big Bounce). So, if the Universe expands and collapses into itself infinitely, then there should be no beginning and no end … subsequently, the definition of age cannot be applied here.

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You may of course argue that the age you are referring to is specific to a single Big Bang/Big Crunch pair; i.e., the one in which we live in, or how far in time we have gone from the last Big Bang.

So how have scientists arrived at answers to the question “How old is the Universe?”

One method is by finding the oldest globular clusters, a dense bunch of stars having roughly the same age. Basically, once you’ve determined their age and picked out the oldest, you’d then be able to set a minimum limit to the age of the Universe. For example, if the oldest globular cluster is found to be 10 billion years, then the Universe can’t be any younger than that.

This brings us to the next queston: How to spot the oldest globular cluster?

According to astronomers, you should be looking for the dimmest bunch in the sky. That’s because the dimmer a star is, the less massive it is. And the less massive it is, the longer it will burn through its supply of hydrogen fuel. Hence, only the oldest stars can burn dimly.

Another method is by determining the current composition of matter and energy density in the Universe then plugging this information into Einstein’s theory of General Relativity to compute how fast the Universe has been expanding. This will allow us to retrace its steps back to the point when time was equal zero.

All the necessary information has been gathered with superb accuracy using the Wilkinson Microwave Anisotropy Probe (WMAP) and is the main reason how scientists were able to arrive at 13.7 billion years.

We’ve got a few articles that touch on how old is the universe here in Universe Today. Here are two of them:

NASA also has some more:

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

Source: NASA

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Tagged as: Age of the universe, Big Bang, milky way