We received the following letter from a young person at school.

Dear Ladies and Gentlemen

I was wondering how old is the earth. Some people say it is 1,000,000 years old and other people say it is 1,000 years old. How old do you think it is and how can we tell? Please write back.

Sincerely

KS, USA

There is no way to directly measure age. We can use rulers to measure length, scales to measure mass, thermometers to measure temperature, etc., but there is no instrument that can measure how old something is.

So if people want to know the age of something, they have to calculate how old it is. There are three main ways of calculating age:

- using historical records and a calendar
- comparing the thing to a similar thing of known age
- measuring the rate of some process, and the amount of product that process produces, and working out how long it would take to produce that amount of product at that rate of production.

All three methods involve making assumptions. Assumptions are things we believe, but which cannot be proven.

For example, to work out your age, you could subtract the year of birth on your birth certificate from the current calendar year. This involves assuming that the information recorded on your birth certificate is accurate.

Another way would be to measure your height and weight, and compare them to the average heights and weights of children of different ages. Whichever age group your weight and height is closest to, you are probably in that age group. This involves assuming that you are average, and that there have been no events in the past, e.g. sickness, that have drastically affected your size.

Another way would be to measure your rate of growth, e.g. measure how big you are now, and how big you are in exactly one year’s time. You could then divide your size now by the change in size since last year to get your age in years. This would involve assuming that you grew steadily at the same rate your whole life, which is an unreasonable assumption. I’m sure you can think of all sorts of events and circumstances that could affect these calculations, causing an age calculated this way to be inaccurate.

When it comes to the age of the world, we can use historical methods (method 1 above), which involve assuming or trusting particular records to be accurate. This is the way we at CMI calculate the age of the earth. We trust the Bible to be a supremely reliable record of world history, and from the information in the Bible we can calculate that the world is about 6,000 years old.

Alternatively, you can measure the rate of change in a natural process, and calculate from that (method 3 above). For example radioactive uranium naturally decays into lead. Scientists can measure how fast this is happening now. They can then measure how much lead is present in a rock, and calculate how long it would take for uranium decay to produce that much lead. This involves making lots of unprovable assumptions. They must assume that all the lead came from uranium, that no uranium or lead entered or left the rock since it was formed, and that the rate of decay has remained constant. All these assumptions are unprovable (and some are extraordinarily unreasonable).

Making assumptions like these, many natural processes still produce ages of just a few thousand years. Only certain radioactive decay processes produce millions and billions of year ages, and if we change our assumptions, we can produce ages this way that match the biblical timescale.

We are all fallen, fallible creatures, scientists included. Many scientists are as unwilling to repent from sin as anyone else, so they don’t *want* there to be a God; they don’t want to be reminded of their sin. So, they are eager to make assumptions that exclude God and with which they can justify to themselves their own sinful natures. So, they focus on certain radioisotope processes that produce Bible-contradicting ages, and ignore the far more numerous processes that produce Bible-compatible ages.

Sincerely

Further reading: see ‘Young’ age of the Earth and Universe Q&A and Radiometric Dating Q&A

For an update on ground-breaking research that strongly questions the assumptions behind long-age radiometric dating and supports the biblical timeframe, see the book, *Thousands not billions*, available from our bookstore.