Uranium Half-Life and Decay
“But thou, Bethlehem Ephratah, though thou be little among the thousands of Judah, yet out of thee shall he come forth unto me that is to be ruler in Israel; whose goings forth have been from of old, from everlasting.”
The half-life is a value which gives an indication of the rate of decay of radioactive isotopes. Radioactive decay occurs in an exponential, rather than linear way. Suppose an isotope, which we will call X, has a half-life of 1 year. If we have 32lb of X today, then in a year, we will have just 16lb – half of 32. In another year, however, we will lose only 8lb more—half of 16. The year after that, there will be 4lb left, and so on.
The term half-life is misleading. Half-life is a notional number, showing how long it would take for half a given radioactive material to decay. When we say that uranium-238 has a half-life of 4,500 million years, this figure is not a problem for creationists. We simply mean that uranium is decaying at a rate, whereby half of it would not decay until 1,500 million years had passed.
Uranium-238 decays into stable lead-206 by a 14 step process. Eight of these steps involves the release of an alpha particle, which is the nucleus of a helium atom. So, every atom of uranium that turns into lead will also yield 8 atoms of helium. An igneous rock should, therefore, contain 8 helium atoms for every one lead atom. Of course, it doesn’t. Helium can escape into the atmosphere. But this means that we can calculate the speed at which helium can leave radioactive rocks. Measuring this speed reveals that uranium must actually have decayed very much faster in the past than it does today.
We thank You, Lord, that You know all things. You are not taken in by human technology today. No true science can or will oppose Your word—though for a season, people sometimes think that they have disproved Your word. Help us to stand strong for You, and to believe all that You have told us. Amen.
Author: Paul F. Taylor
Ref: Humphreys, R. (et al), Radioactivity and the Age of the Earth, (ICR). Image: US DoE, Public Domain.