Hey, there!

Thank you for writing!

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Well, Anon, that statement is inaccurate.

Not all creationists believe that the Earth/Universe is 6,000 years old.

I need to stress that this is a non-issue in terms of salvation, veracity of the Bible, and other, more central things, in Christianity. It’s a differing issue amongst Christians, but it’s not one so huge that it causes rifts between us. At least, it shouldn’t be.

Now, as a Physicist, I know there are different ways to measure the age of the universe. There are four main ones, each independent of each other, that reach the same conclusion: Everything’s been around for about 13.7 Billion years.

How do I know?

Method #1: Expansion Rate.

The universe is constantly expanding (like a balloon when someone blows into it). That means that if we know how fast it is expanding, we can mathematically reverse the expansion until the universe reverts back to it’s beginning.

How do we calculate this expansion? Measuring the distance from other galaxies to our own and observing how fast these other galaxies are moving away from us. If we know the distances and velocities of enough galaxies, we can calculate the expansion rate of the universe, and thus the age of the universe.

And we do.

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Method #2: Cosmic Background Radiation Temperature.

I believe that, for the universe to have been created ex nihilo, God used a lot of energy. A lot. Energy makes heat. So, a LOT of energy makes a LOT of heat. Ever since Creation, though, the Universe has been cooling down.

When we measure the cosmic background radiation (or, you know, “take the temperature” of the universe), the readings indicate that the temperatures all around us are about -455ºF (that’s jut 2.725ºC above absolute zero!!). Interestingly enough, these temperatures vary little; in fact, less than 1 part in 10,000. Given the geometry of the universe and these temperature readings, we can calculate for how long the universe has been cooling, and thus, know the age of the universe.

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Method #3: Age of the stars

Stars are simple objects. They are 100% gas, burning through the process of nuclear fusion. This process is very well understood and experimentally verified.

It’s because the process of stellar burning is so well understood, that we can determine the age of a star if we knows the mass, color, and brightness of the star (all of these characteristics can be measured from your local observatory).  From this data, we can know how long the star has been burning. This places a boundary on how old the universe must be, since it can’t be any younger than the oldest star.

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Method #4: Measuring Relative Quantities of Radioactive Isotopes

As you might imagine, this one’s a little technical. Radioactive isotopes are, basically, the crazy cousins of any given element of the periodic table. They have a different mass than their normal counterparts and their nuclei are unstable. Radioactive isotopes get rid of excess energy by shooting off alpha, beta and gamma rays - which are the building blocks of comic book heroes.

Now, radioactive isotopes are produced by supernovae, which are supergiant stars in their last stage of burning off their gases.

It turns out that radioactive isotopes decay at rates (half-lives) that are well understood. Uranium and thorium, for example, have half-lives of billions of years. So, since we still find uranium and thorium in the universe, we know that the universe cannot be so old that these isotopes had completely decayed out of existence. That sets an upper limit to the age of the universe of a few hundred billion years.

HOWEVER, there are isotopes that have much lower half-lives. So, isotopes with half-lives of millions of years or less (like plutonium, neptunium or technetium) cannot be found here on Earth. Why is this important? This is how we know that at least one billion years have gone by for them to have disappeared. These extinct (on Earth) isotopes were produced by ancient supernovae. By measuring the amounts of these isotopes in existence today, we can calculate how much time has passed since the first supernovae produced the first isotopes. So, the Earth is at least a couple of millions years old. Obviously, the universe must be older than this.

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I hope you were able to follow, at least at a basic level, these four methods. Like I said, there are many other independent methods that have been used to calculate the age of the universe, but these four are the simplest. What’s interesting about these methods is that they rely on different and independent measurement techniques, but they all arrive at the same answer for the age of the universe – around 13.7 billion years.

Obviously, it’s easy to attack one measurement technique as being inaccurate. Four, though? That’s when you need to pay attention - especially since they all arrive at the same answer. The laws of physics used to date the universe are very well understood and experimentally verified to a great degree of precision. So, in my opinion, to dismiss all of these independent measurements as “erroneous” simply displays a lack of understanding of physics and mathematics.

But that’s just me.

Now, let me say this again: the age of the universe (or Earth) does not undermine Scripture - at all.  Whether the universe is 13.7 billion years old or 6,000 years old has no bearing on the truths taught in the Bible.  As Christians, we are to seek out the truth, no matter what it may be. The findings of science will never the contradict the Word of God, so engage with science and enjoy the discoveries that lie ahead of us.

It’s fun to see the creativeness and limitless power of God at work in things like the universe… or your heart ;-)

God Bless and have an awesome day!!