How Old Is the Earth?
By Merle Hertzler
Last night, light arrived at your house from the distant stars. It must have taken a long time for that light to reach your house, for the stars are very far away, and light travels at only 186,000 miles per second. Scientists tell us it would have taken billions of years for the light to have made that journey from the distant stars. If the light did indeed come from those stars, then the light left those stars billions of years ago. And if the light was traveling for billions of years, than the stars must be very old, and the universe is very old.
Some people will object to this conclusion, and will tell me the universe is only 6000 years old, based on a literal interpretation of the Bible. But if the universe and the stars are only 6000 years old, and light appears to have taken billions of years to make that journey, how did that light manage to reach the earth?
Creationists have made several attempts to explain this problem. Some have questioned that the universe is really that big. If the stars are closer to us than scientists claim, then the light would have had time to reach earth in 6000 years.
So how can scientists be so sure the stars are far away? Good question. Let's look at one measurement that was made. On February 23, 1987, a supernova, which is a vast star explosion, was observed. It was known as SN 1987A. About eight months after the explosion was observed, reflections from the explosion were seen in a distant gas cloud ring that circled the supernova. The ring can be seen as an orange circle in the photo above. The reason the reflected light was delayed eight months was that it took time for the light to travel from the supernova to the distant gas clouds and then to reflect from there back to earth. (See illustration below.) And so we can conclude that it took about eight months--or 0.66 years-- to journey from the supernova to the gas ring. Knowing the time it took to reach the ring, and knowing the speed of light, we can calculate the distance to the ring. Knowing this distance, and measuring the angle between the supernova and the reflection as seen from the earth, we can use simple trigonometry to calculate the distance of the supernova from the earth. Astronomers have calculated that the distance is so large that it took light 169,000 years to make that journey.
So if you think the universe is 6000 years old, how is it that we can see this supernova and the reflected light? The light had to travel for 169,000 years to reach earth. It must have left the supernova long before the traditional date of Creation, 4000 BC. Can you see how most of us conclude the universe is more than 6000 years old?
Some will suggest that God made the universe complete with a beam of light from the stars to the earth. The actual light that arrives here would have never left the stars, but would have been created midway. It would be like a truckload of Florida oranges that made it to Vermont in 1 hour because the truck and the oranges aboard had been created out of nothing 20 miles away from Vermont. But if this had happened, then the truck does not have oranges from Florida onboard. It would be carrying oranges that had been created enroute. Similarly, if the light was created enroute, the light would not have actually come from the stars.
There is a big problem with this view. We are not merely seeing a simple beam of light. We see events such as this supernova explosion in the light that arrives. Did these explosions really occur? If the light was created part way between the star and the earth in such a way that it looked like an explosion, then it seems that the creator was deceptive. For to create light that looks like an elaborate explosion, when no such explosion really happened, would be deceitful. If the creator was deceptive, would he blame us for being fooled by the deception he made?
Suppose that God had deliberately faked the light of an explosion that had never happened. If he did this, how would we know anything about the universe? Once we postulate that an all-powerful, deceptive God is manipulating the data, we could know nothing. Such a God could be fooling us in everything we observe. We may think lightning is made of electricity, but if a deceitful God is in charge, maybe his is only fooling us. We may think the laws of physics apply, but a deceitful God could be manipulating the data. So if God is all-powerful, and is deceitfully manipulating the data, we would know nothing.
If we rule out a deceitful God, than it seems that the distant star light has been traveling for millions of years.
Did light manage to get here in less than 6000 years because it used to travel faster? This is an old Creationist claim, which has been thoroughly refuted [1 ]. In this case, however, even a faster speed of light would not help. Light from the supernova took 8 months to reach the outer ring. Suppose light was traveling ten times as fast when it started its journey. Then the light would have gone ten times further during that 8 months it took to reach the cloud ring, and the ring would be ten times bigger than we have calculated. This would mean that the triangle in the illustration above is ten times as big, and the distance to earth is ten times as far. This only makes the problem worse! Now the light would need to travel much further to get to earth. So even if the light had started out faster, it would not resolve the problem for believers in a 6000-year-old earth.
So the light we see in the photo above simply could not have made it to earth if the universe is less than 169,000 years old. Something is wrong with the 6000-year time frame.
I use SN 1987A as an example because it was in a galaxy that was close enough that we could photograph it. We can see that other supernovas are occurring much further away. The light that arrives from the most distant stars would have taken billions of years to reach earth. And yet we see it. Can you reach any other conclusion but that the universe is billions of years old?
Let us pause for a minute to address a concern that may be on your heart at this point. The conclusion of an old earth will not be easy for many Christians to reach. You have a high regard for the findings of true scientific observation and reason, but you also trust the Bible. And your Bible seems to indicate that the universe is thousands of years old, not billions. And so you are faced with a conflict. One solution would be to just ignore the physical observations of the universe. Another solution would be to just ignore the Bible. Neither of those is satisfactory to you. There are some other options. Either you could modify your observations of starlight so that it is compatible with your interpretation of the Bible, or you could modify your interpretation of the Bible so that it is compatible with the physical observations. We have tried to modify our observations of the universe to match a 6000-year-old earth, and failed. So the natural question for many Christians to ask next is, "Can the Bible be interpreted to be compatible with an old universe."
Many Christians have found that the Bible can indeed be interpreted that way. For instance, Norman Geisler, one of the foremost Evangelical apologists, writes:
Notice that this quote does not come from a godless, atheist infidel. No, it comes from a leading Evangelical authority. He finds that an old earth causes no problem with the Bible. And many leading Evangelical scholars have been publicly open to an old-earth view, including Lee Strobel, John Ankerberg, Pat Robertson, William Lane Craig, Hugh Ross, Hank Hannegraff, and Francis Schaeffer. (See sidebar)
There are several ways in which the Bible can be interpreted to be compatible with an old universe. One of the most popular is to assume that each "day" in Genesis actually represents a long period of time. Other options have been proposed. If your interpretation of the Bible is making it difficult to accept the obvious conclusion from nature, you may want to look at some of the links in the sidebar before you proceed.
Moving on, not only do we find that the stars are old, but we can see that the earth is old. All around the world we find many layers of underground fossils and sediments. Where did all of these fossils come from? Glenn Morton, a former young-earth Creationist writer, has written a description of the fossil record as it appears in North Dakota. He describes the 3-mile thick fossil record, which includes animal fossils, burrows, shark teeth, coal, and fecal pellets (click here to see it offsite). Where did all of these layers come from? How is it that we find animal fossils, teeth, and fecal pellets spread throughout the record? It is difficult to escape the conclusion that all of these are the remains of real animals that were buried. But if animals have been buried 3 miles deep, and other animals have been buried on top of them, and still others on top of them up through all 3 miles of sediment, one must surely conclude that it took a long time for all of those layers to accumulate.
Let's look at another example of the details found in the fossil record. Specimen Ridge in Yellowstone Park is a 2000-foot high wall of rock that includes the petrified remains of 18 forests, each one growing on sediments that were deposited on the forest layer below it.  Now think about that. A forest grew and was covered up in a catastrophic volcano and landslide. The soil weathered until it became fit for plant life to grow again. Another forest grew. Some time later it too was wiped out in another catastrophe. The process repeated until at least 18 forests grew and were wiped out. Surely it takes a long time for one forest to be covered, for the soil to weather, and for another forest to grow above it, only to be covered up again. Do you not agree that the bottom of this ridge--down below those 18 fossilized forests--is very old?
How can young-earth believers explain the fossil record? Some have tried to say that God created all of these layers at the beginning of the world. But is that logical? Are we really to believe that the fossil bones of dinosaurs and buried forests were put into the rocks at the creation of the world? That would mean that those dinosaur fossils did not come from real animals. Is it possible that God just buried all of those fake fossils down there? That doesn't seem likely. Could God be so deceptive? And you do not believe in a deceptive God, do you? So you must conclude that the fossils are real, and that the rocks in which dinosaur fossils were found were formed after those dinosaurs had lived and died. So many rocks down there could not have been formed during a one-week creation, but were formed later, after the dinosaurs they cover had died.
Now the same reasoning that makes me think that the dinosaurs were real, also convinces me that the fish and trilobite fossils found far below the dinosaur fossils are also the real remains of real animals that once lived. And so these rocks must also have been formed long after the origin of the earth. These fossils simply could not have existed in the earth from the beginning. They must have been created later, and they must have taken some time to form.
Some young-earth creationists have tried to argue that the bulk of the fossil record was formed during Noah's flood, a view known as flood-geology. I had read such books as a teenager, and was convinced that they described the way the fossil record was formed. Years later, I would find that the problems with this view are insurmountable. For instance, in the middle of the Grand Canyon we find a buried sand dune, which was made of wind-blown sand. Now flood geologists claim that the rock layers in the Grand Canyon were created during Noah's flood. But if those rock layers were formed during the flood, why do we see buried sand dunes in the midst of the deposits? Something is wrong here. Surely there were no winds blowing sand around under the flood waters. How then is this dune in the middle of the deposits? If this dune occurred before the flood, how can you explain all of the fossil-bearing layers below it? And if the dune occurred after the flood, how can you explain all of the layers above it? Where did they come from? So a global flood does not explain the fossil record.
And what about the cave systems, footprints, and animal burrows that we find throughout the fossil record? How can these things be created during a raging flood? Animals would not be walking around leaving footprints if a raging flood was going on above them, would they? And how can a cave possibly get created in the middle of a raging flood? So it seems to me that the flood cannot explain the fossil record. The layers of rock must have been formed over a very long period of time.
How old is the earth? Surprisingly, modern science has been able to answer that question to a high degree of accuracy. A technique known as radiometric dating is used to find the age of the rock layers. These dates are based on the knowledge that some elements in rocks decay to form other elements. We know how fast they decay. Thus, if we know what the original concentrations of the elements in a rock were, and know what the concentrations are today, and if we can establish that there were no outside disturbances that interfered with the process, we can calculate the age of a rock. That sounds like a lot of unknowns. Young-earth Creationists love to point them out as if scientists had never thought about them. They are wrong. Scientists have dealt with these problems, and have found solutions.This gets a little technical here--skip this paragraph if I lose you-- but I think we should take a brief look at Rb-Sr isochrons. This was the clincher for me. I had once argued that the earth is young, but when I learned about isochrons, I soon changed my mind. Scientists use isochrons to calculate the original composition of certain elements in a rock, and to show that contamination has not affected the result. Does that sound like magic? It isn't. It turns out that the element rubidium-87 (Rb-87) in rock decays to form strontium-87 (Sr-87) at a known rate. The more Rb-87 in a rock, the faster Sr-87 accumulates. So if we know the concentration of Rb-87 of any sample, we will know the rate at which the Sr-87 concentration increases with time. And knowing this rate of change, we can calculate back to any time in the past and determine what the Sr-87 concentration would have been. Rocks also have another form of strontium, Sr-86, which stays constant with time. Scientists measure the amount of Sr-87 in a rock by looking at the Sr-87/Sr-86 ratio. As Sr-87 accumulates, the Sr-87/ Sr-86 ratio increases. What does this tell us? One sample doesn't tell us much. Let's look at another sample from a different location on the same formation where there is more Rb-87. This point will experience a faster change in its Sr-87/Sr-86 ratio because there is more Rb-87 to decay. Again, we can calculate this ratio back through time. In a valid sample, we will find that, at some point in the distant past, both samples had the same Sr-87 /Sr-86 ratio. Scientists can repeat the process for a number of samples on a valid rock formation, and all will show that they had nearly the same Sr-87/Sr-86 ratio at that point in the past (see graph below). This is interesting. For, in rock formations that come from a single flow of lava, the strontium comes from one source, and would indeed have had the same Sr-87/Sr-86 ratio throughout when the rock layer was formed. The most obvious reason for the correlation of these ratios is that this is the point when the lava that created this formation was flowing, with strontium from one source spread throughout the lava. So this must be the date of the lava flow. This procedure yields ages of many millions of years.  What other explanation is there? Could God have scattered these elements in the rocks at different concentrations, using a different Sr-87/Sr-86 ratio at each point depending on the local Rb-87 content, so that it looks like the rocks existed through millions of years of decay? Wouldn't that be deceptive?
We have looked at only one method of dating rocks. There are more than 40 radiometric dating methods. Scientists usually do more than one test on a rock formation, and find excellent correlation between the dates found. With so many different methods--each based on different principles--and with each arriving at the same answer, isn't that strong evidence that the dates found are correct?
Even if you do not understand the concepts, there are thousands of scientists that do. And there is a scientific consensus that radiometric dating is valid, and that these rocks are many millions of years old.
It is important to understand that there are animal fossils under these rocks. Now you agree with me that these fossils were formed from the remains of animals, don't you? And you surely must agree that the rocks on top of those animal fossils must have been deposited after those animals had lived. So the rocks on top of the fossils--the rocks that we evaluate with radiometric dating--could not have been formed when the earth was first formed. They must have been formed later. If we were to suggest that God deliberately manipulated the elements to change the apparent date, it would mean that he did it when the volcano that formed those rocks erupted many years after the earth began. Did God manipulate the data hundreds of times throughout the ages as these various rocks solidified? I cannot imagine God doing that, can you? Surely he would not be bothered with deliberately manipulating the data every time a volcano erupts.
I can only come to one of two conclusions. Either those rocks are many millions of years old, or God used extremely elaborate means to make the rocks look old. The deception would be so subtle that nobody could have possibly been fooled by it until scientists had reached the modern understanding of radioactivity. Could God have deliberately faked all of these components of all of these rocks, just so we would arrive at the wrong answer when we tried to date them years later? That doesn't seem likely to me. If we rule out deliberate deception, I am left with believing that the rocks are old.
Some have proposed that these rocks are not the work of God, but of the devil. Okay, suppose that a volcano erupts in Hawaii. Do a host of demons swarm over the lava to manipulate the elements and make it look old? Science cannot seem to detect such demons. Besides, if demons are doing that, shouldn't the rocks from recent volcanoes date to millions of years old? Rocks from recent volcanoes do not yield old ages when tested. Have the demons forgotten to manipulate the elements? Okay, we could postulate that these demons worked only in the distant past. But then I need to ask why there is so much volcanic rock down there if the earth is 6000 years old. Yes, we could postulate that another swarm of underground demons was down there causing volcanoes. Then I would ask why we find no mammals or people in the older layers. Again, we could postulate yet another host of demons, who chased all of the mammals away from the early volcanoes. We could continue to postulate yet another demon for every problem with this hypothesis. Do you see how throwing all of these demonic entities into the solution makes it all implausible? Every time we add yet another demon to fix a flaw in the theory, the whole theory becomes less likely. William of Occam discovered long ago that simple explanations are usually more likely to be true than explanations that require multiple ad hoc explanations. Once we start multiplying entities--once we add one demon after another to explain each detail--we could prove anything. We could state, for instance, that the earth was flat, and could propose a different demon for every evidence to the contrary. If that is acceptable, no idea could then be proven false. We would know nothing. So scientists look for the simplest explanations, the ones that do not need multiple ad hoc assumptions.
The simplest explanation is that the rocks look old because they are old.
How old is the earth? Rocks on the earth have been dated as old as 4 billion years. Many meteorites have been dated, and we consistently find an age of about 4.5 billion years. Evidence indicates that the meteorites and the earth were formed at about the same time, about 4.5 billion years ago.
Perhaps you are not into the study of radioactive elements and exponential decay. How about counting? You can certainly do that. If you were to cut down a tree and count 100 rings, you would know that this tree was 100 years old. We can do a very similar thing with the polar ice caps. The ice builds up another thin layer every year. People have drilled down through the ice and counted the layers. They find more than 50,000 distinct layers before they begin to fade together. Doesn't that prove that the earth is more than 6000 years old?
Years ago, organizations like the ICR had convinced me that the earth was young. They used arguments that sounded good when I heard only one side. They told me, for instance, that the earth's magnetic field was decreasing. They said that the magnetic field must have started out strong several thousand years ago, and decreased since then. That sounded convincing to me. Since I, who knew little about the earth's magnetic field, was convinced by their argument, did that prove that the argument was correct? Of course not. The real test of a scientific proposal is not the ability to convince the general public, but the ability to convince those that understand the relevant data. Those that understood recognized that the claim for a constantly decreasing magnetic field was false, for it did not account for all of the components of the earth's magnetic field, and did not recognize the evidence that the magnetic field has been fluctuating throughout earth history. Those who understood the earth's magnetic field were not convinced with this young-earth argument. You may hear arguments from the young-earth crowd that sound impressive. Please understand that scientific-sounding arguments that convince the general public do not prove a concept is true. An idea should be considered scientific only if it stands up when those who understand the science involved analyze it and accept it. That is the real test.
I conclude that the universe is very old. We can see distant starlight. We can dig up old fossils and date rocks to billions of years. And a lot can happen in a billion years.
1. Measurements throughout history have shown that the speed of light is constant (see The Decay of c-Decay by Robert P. J. Day). Observations of distant objects show that the speed of light was the same for billions of years (see Dealing with Creationism in Astronomy by W.T. Bridgman). The speed of light is so reliably constant, that the meter is officially defined as the distance that light travels through a vacuum in a specified fraction of a second. (see Is the Speed of Light Constant?)
4. The science of isochrons involves much more than what I discuss here. In practice, scientists plot the Sr-87/ Sr-86 ratio against the Rb-87/ Sr-86 ratio on a graph and use the slope to determine the age based upon these principles. For more details, seeIsochron Datingby Chris Stassen.
CopyrightÓMerle Hertzler 2002, 2004, 2006. All rights reserved.