Students ask: “Does radioactive dating prove that Earth is billions of years old?”

The 10th-grade California textbook, Biology by Miller & Levine, uses radioactive dating as confirmation of evolutionary time. “[Radioactive dating] could have shown that Earth is young. If that had happened, Darwin’s ideas would have been refuted and abandoned. Instead, radioactive dating indicates that Earth is about 4.5 billion years old—plenty of time for evolution by natural selection to take place.”1 What does radioactive dating really show?

Radioactive dating uses radioactive elements in rocks, elements which transform into other elements (decay) over time, to estimate their ages. Here’s how it works: First, the parent-daughter element ratio is discovered. This is the number of parent elements (original radioactive element) to daughter elements (what the parent element turns into). The time it takes for this to occur is estimated using a half-life, the time it takes for half of the remaining parent elements to turn into daughter elements. The radioactive “clock” is then reversed to the time when the rock supposedly formed, and an age-date is obtained.2

However, this method makes 3 big assumptions in order to work:

  1. The amount of daughter elements in the original rock is known.
  2. No parent or daughter material was added or removed from the sample over time.
  3. The rate of decay is constant; it never happened faster or slower in the past.3

Since these are all unknowns, we cannot use radioactive dating as an ‘absolute dating’ method. In addition, radioactive dating has been shown to yield incorrect dates for rocks of known age. For example, volcanic rocks formed at Mt. Saint Helens during the 1980s have registered radioactive ages at 0.5-2.8 million years old!4 If we can’t trust radioactive dates for rocks of known ages, why should we accept dates for rocks of unknown ages?


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Also, different dating methods often give conflicting results. For example, radioactive dating of rock samples taken from the Cardenas Basalt of Grand Canyon produced the following results:

METHOD                                           ISOCHRON “AGE”

Potassium-Argon                             516 million years

Rubidium-Strontium                        1,111 million years

Samarium-Neodymium                  1,588 million years4

Lastly, there is evidence that decay rates have not always been constant. Using the uranium-lead dating method, scientists dated zircon crystals in granite at 1.5 billion years old, however, these same rocks contain a large amounts of helium (a daughter element of uranium decay which escapes quickly over time) which indicates an age of only 6,000 years!6,7  This means that 1.5 billion years of radioactive decay must have occurred in only 6,000 years!

Obviously, radioactive dating has not proven to be a reliable method for dating rocks. Instead of relying on man’s fallible ideas (such as millions of years of evolution), we ought to trust what God’s Word says about science and history.

Free resources for further research:

Chapter 3: The Age of the Earth, Dating Methods, and Evolution

Does Radiometric Dating Prove the Earth is Old? 

ICR: Doesn’t Radioisotope Dating Prove Rocks Are Millions of Years Old?

Video: Radiometric Dating


1Miller, Kenneth R., and Joseph S. Levine. Miller & Levine Biology. Boston, MA: Pearson, 2006. 466. Print.

2Tarbuck, Edward J., and Frederick K. Lutgens. Earth, an Introduction to Physical Geology. Upper Saddle River, NJ: Prentice Hall, 2005. 284-90. Print.

3Snelling, Andrew A. Earth’s Catastrophic Past. Vol. 1. Dallas, TX: Institute for Creation Research, 2009. 800. Print.

4Ibid, p. 841.

5Ham, Ken. The New Answers Book 1: Over 25 Questions on Creation/Evolution and the Bible. Green Forest, AR: Master, 2006. 118. Print.

6Morris, John D. The Young Earth. Green Forest, AR: Master, 2011. 53. Print.

7Snelling, 2009, p. 846.