One in a series of letters to my son that I wrote to strengthen him as he began his high-school years
Your science textbook asserts an age of 4.5 billion years for Earth. Your book cites radiometric dating as the basis for that age. But beware! The complicated science and math behind radiometric dating lend an appearance of precision and authority that is far from deserved.
1. That 4.5 billion years comes from outer space
It's true. We get the 4.5 billion years from space. A man named Claire Cameron Patterson was the first to compute a 4.5 billion-year age for Earth. He did that by measuring radioisotopes in a rock from outer space—the Canyon Diablo meteorite.
Why a rock from outer space? Here's the explanation from the current (24 December 2010) Wikipedia article Age of the Earth:
"Most geological samples from Earth are unable to give a direct date of the formation of Earth from the solar nebula because Earth has undergone differentiation into the core, mantle, and crust, and this has then undergone a long history of mixing and unmixing of these sample reservoirs by plate tectonics, weathering andhydrothermal circulation."
In other words, Earth rocks have changed so much during the supposed billions of years as to be unreliable; the assumptions underlying radiometric dating won't hold.
There are two problems with the above logic: 1) The logic is circular. Notice the mention of "long history". Patterson assumed an old age before having made the measurements to establish it. 2) It's just plain silly on its face to measure something not from Earth. When you're sick, I take your temperature, not the dog's.
2. Your book describes the wrong dating method
Your book introduces the 4.5 billion-year age, and immediately follows-up with a description of potassium-argon dating. However, potassium-argon dating is not the basis for Patterson's 4.5 billion-year age. Patterson relied upon uranium-lead dating. I have no idea why your book's authors chose to support a uranium-lead date by describing the potassium-argon method.
3. Potassium-argon dating is not cut-and-dried like your book suggests
Lava from Mount Saint Helens' eruption in 1986 has been measured at 335,000 years of age using the potassium-argon method. (Read Steven A. Austin's paper: Excess Argon within Mineral Concentrates from the New Dacite Lava Dome at Mount St. Helens Volcano). That result is an over one-million-percent error! (1,295,733% to be exact).
I remember the Mount Saint Helens eruption. And I know with certainty that I am not 335,000 years old. Why would any thinking person put their faith into a dating method that is one-million percent wrong in dating a recent, known event?
4. Radiometric dating is not done blind
A reliable dating method should yield a correct answer without knowing the answer ahead of time. Yet radiometric dating labs often ask for an estimated age, or for indication of age such as the rock layers involved. For proof, just look at the Sample Submission Form used by the University of Georgia's Center for Applied Isotope studies. Look at the bottom of page 1, in the section on sample information. You'll see a field for "Est. Age".
Imagine the following conversation:
Geologist: I have a rock. I'd like to know how old it is.
Lab technician: Excellent! I have a reliable method for determining age.
Geologist: Good. How do we begin?
Lab technician: First, you tell me how old you believe your rock to be.
Geologist: I believe my rock is 5-10 million years old.
Lab technician: Then I show your rock to be 7.5 million years old.
Geoligist: Uh, er,...
Lab technician: That'll be $5000.00 please.
Would you pay the $5000? Or is the word "scam" running through your mind?
5. Radiometric dating rests on assumptions that are increasingly questionable
Radiometric dating requires that: 1) you know the initial composition of a rock sample, 2) the sample was never contaminated, and 3) the decay rate never changes. Andrew Snelling's article Radiometric Dating: Problems with the Assumptions goes into detail on indications that these assumptions are flawed.
6. Geologists know better
Geologists know about the problems in radiometric dating. They don't accept radiometric dates at face value. Here's what a geologist really does:
- Work out the age of a rock by looking at how and where the rock is found in the field.
- Send the rock for radiometric testing.
- Ignore or explain-away any results that disagree with the estimated age from Step 1.
Tas Walker's article explains in more detail: The way it really is: little-known facts about radiometric dating.
7. Evidence abounds for a young Earth
Son, your textbook ignores evidence for a young earth. But the evidence is there! The evidence is all around us. There is not enough sodium in the sea for an old earth. There is not enough sediment in the oceans for an old earth. Our magnetic field is decaying too fast. And my favorite of all: there is too much helium. Read about these and other evidences in D. Russell Humphrey's paper: Evidence for a Young World.
Radiometric dating as it's currently practiced flies in the face of abundant evidence for a young Earth. Radiometric dating rests upon assumptions that are crumbling under scrutiny. Don't let the imposing math and science of the method sway you into believing that radiometric long ages are true.