Suppose your child walks up to you and says he feels bad. You place your hand on his forehead and sure enough, it’s hot.
Worried, you break out an oral thermometer, and after two minutes it reads 102.2 degrees F. Just to be sure you try a fancy, in-ear device that tells you his temperature is 102.0.
Does your boy have a fever? Yes. Three independent measurements tell you so. There is no way all three methods are wrong.
To be sure, they are not equally reliable and the numbers you get are somewhat different, but you can say with confidence that his temperature is in the neighborhood of 102. It might be 101.9 and it might be 102.3, you can’t say for sure, but it doesn’t matter because you know what you need to know: It’s time to take him to the doctor.
This is similar to why we think the universe is about 13.8 billion years old. Like the 102-degree fever, this figure comes from a number of different kinds of measurements.
Three of these are: (1) observations of a class of stars called white dwarfs, (2) details of something called the cosmic microwave background, and (3) the recession velocities of distant galaxies.
These methods all point to an age in the neighborhood of 13.8 billion years. If the age of the universe is significantly different than this, then these methods — and several more I have not mentioned — must not only be wrong individually; they must be wrong such that they all give the same result.
But, as in the case of the sick child, these are independent observations. They do not depend on the same assumptions or observations, so the probability of them all giving the same wrong answer is zero.
Also, just as in the measurement of the child’s temperature, different methods give us slightly different ages. The universe might be 13.7 billion years old according to one method and it might be 13.9 billion according to another, but we know what we know: the cosmos is billions of years old.
This does not square with a face-value reading of scripture. If you take the Bible and simply count back the years from the time of Jesus, you will find that creation week occurred about 6,000 years ago. Many people believe this is an accurate date for the origin of the universe. But this obviously contradicts the scientific consensus.
There is more. A different (and much larger) group of independent observations does not tell us the cosmos is 13.8 billion years old, but do tell us it is more than 6,000.
Three of these are (1) measurements of the distances of nearby stars, (2) surveys of radioactive nuclei found in the Earth’s crust, and (3) the drifting of continental plates. Again, these methods independently point to the same conclusion: the Earth and the cosmos have been around longer than 6,000 years.
You also ask about the size of the universe. Its size is related to its age.
The cosmos has been expanding for the last 13.8 billion years and by now it is quite large, many billions of light years across. There is a host of overlapping methods for determining distances to stars and galaxies, and they work together to form something called the “distance ladder.”
The distances to the closest stars are measured by a simple approach called parallax. Our eyes and brain use parallax to produce depth perception for nearby objects.
More distant objects require other methods. Some of these methods are more reliable than others, but constant progress and cross-checking mean that the distance ladder gives better and better results over time. This progress is largely due to advances in telescope technology and refinements of observing methods.
There are of course assumptions behind all of this. For example, we assume that the speed of light is constant; that is, it was the same a billion years ago as it is today.
We also assume that rates of radio-activity have not changed over time and that the physics that applies out there is the same as the physics that applies here on earth. Scientists are keenly aware of these and other assumptions and are constantly testing them.
So far they have stood all tests. One hundred percent certainty is not possible in science, but we have good reasons to believe our assumptions are reliable.
We have another reason to trust our assumptions: they have led us to a self-consistent understanding of the cosmos. For a simple example of this, the age of the earth is less than the age of the universe, even though the ages of both are determined in completely different ways.
Also, the age of the universe is greater, but not much greater, than the age of the oldest stars. And the time required for stars to produce the elements needed for life is far less than the age of the universe.
And the methods of determining distances to celestial objects such as stars and galaxies overlap and fit together, and are doing so better every day. The list is nearly endless.
To be sure, there are still pieces of the puzzle missing. Major questions are still being asked. This is to be expected — it has always been so.
But the sense one gets from looking at the scientific work of the last five centuries is that of consistency and fruitfulness. This would be quite surprising if our assumptions were all wrong.
There is of course a simple argument available to anyone who disagrees with the conclusion of such an ancient and vast universe: perhaps God made the cosmos appear to be much older than it is, much as Genesis describes Adam and Eve as being formed as a man and woman and not as children.
And perhaps God made the cosmos appear to be many billions of light-years across. Maybe light from distant stars and galaxies was created in mid-flight. Maybe South America and Africa were formed to look exactly as if they were part of a single original continent and have been drifting apart for 200 million years. Maybe the comic microwave background radiation, which scientists believe is a relic of the Big Bang, was put in place to make it look as if the cosmos was 13.8 billion years old.
Maybe, but this is deeply problematic.
There might be theological and poetic reasons to describe Adam and Eve as a man and woman, but what would be the point of God deliberately adjusting the actual cosmos to appear in every detail to be 13.8 billion years old? To test our faith?
I just can’t agree with that. Any God who would manipulate the universe in such a way — just in order to test us — is not a God who can be trusted. That God would be an anti-rational agent of disorder.
That God would be rooting for us to reject our own God-given capacities for reason, imagination and creativity. That God would be a deceiver.
And that is not the God of life and love and reason and wonder in whom we all believe. NF
By Paul Wallace