Radioactive Half-Lives Not Affected by Earth/Sun Distance

The international symbol for radiation, which is also known as the trefoil.

The international symbol for radiation, which is also known as the trefoil.

Several years ago, data came out of Purdue University, indicating that the half-lives of some radioactive substances are affected by the distance between the earth and the sun. Despite the fact that most scientists thought there were problems with the experiment, the group continued to publish pretty convincing data supporting their case. Based on their data, I thought their conclusion was well-founded. However, it looks like they (and I) were wrong.

I first noted that there might be a problem with their conclusion over two years ago, when other researchers tried to duplicate their results using a more precise technique. They found small changes (significantly smaller than the Purdue group) and no indication that those changes were correlated with the distance between the earth and the sun. Since then, two more papers have been published that pretty much seal the case that the Purdue results were wrong.

The first paper comes from NIST, the National Institute of Standards and Technology. Since NIST is responsible for all sorts of standards, several of their groups monitor radioactive isotopes for extended periods of time. They are also concerned with precision, so their procedures are focused on making sure there are no outside influences acting on their experiments.

Their paper reports on the results of experiments carried out in 14 laboratories across the world. A total of 24 different radioactive isotopes were studied, including those that decay by alpha emission, beta emission, electron capture, and positron emission. Some experiments covered “only” 200 days, but others covered four decades! Eleven different experimental techniques were used. All of the experiments saw very small variations (less than one-hundredth of one percent), and none of them saw any correlation between those tiny variations and the distance between the earth and the sun. In addition, the variations were different from experiment to experiment, so the most likely explanation for them is variation in the instruments that were used.

While the NIST paper obviously makes a strong case that the Purdue results are not real, I think a more recent paper gives us the final word. The authors used the same detection technique as the Purdue researchers, but they performed the experiment in a sealed chamber that had constant pressure, humidity, and temperature. They studied five radioactive isotopes for over a year, and like the NIST teams, they saw only small variations that were not correlated with the distance between the earth and the sun. This indicates that whatever the Purdue researchers saw was related to changing weather conditions, not changing radioactive half-lives.

While it would have been exciting for radioactive half-lives to be dependent on the distance between the earth and the sun, it almost certainly isn’t the case.


  1. Jon says:

    Dr. Wile,

    You are one of the only bloggers that I can rely on to not spin or ignore results. Thank you for your humility and desire for honest understanding.

    I was curious about this remark: “This indicates that whatever the Purdue researchers saw was related to changing weather conditions, not changing radioactive half-lives.” Would the atmospheric conditions in this case be affecting the instruments, causing inconsistent results? If that is the case, it should be demanded that all dating isotope measurements take place on equipment in stable conditions.

    1. Jay Wile says:

      The detectors used in the Purdue experiment were filled with a gas, and they detect the presence of radioactivity by detecting ionization in that gas. The temperature will affect the pressure of the gas, and the humidity will affect how easily the gas is ionized. The exterior pressure can also have an effect at the “window” where particles enter. So yes, atmospheric conditions can play a role.

      Now, the level of these effects (even in the Purdue experiments) is relatively small, so when the precision doesn’t have to be extremely high (and it doesn’t for many experiments), the atmospheric effects aren’t worth controlling for. The Purdue team thought they had controlled for them by exposing the detectors to a constant level of radiation periodically and seeing that their response stayed the same. Obviously, they didn’t do that as well as they needed to.

      When it comes to dating, any effects like these should average out, because the time spans are very long. Even if the Purdue team was right, the variation they saw averages out over the course of a year. Thus, these kinds of effects aren’t important in radioactive dating.

  2. Tom Shipley says:

    Jay, what is the radioactive element that was used and was it the same as the previous experiement? What about the report claiming that a solar storm in 2008 was preceded by a spike in manganese-54 decay rates? Is there still perhaps some kind of solar connection regarding SOME radioactive materials but not others?

    1. Jay Wile says:

      The studies that found no solar influence studied all the isotopes that the Purdue group studied, and several others. The 2008 report about the solar flare was done by the Purdue group. Some of the NIST experiments were going on in 2008, and they saw nothing. Obviously, one can’t rule out some effect in some situations, but the entire issue started with the Purdue experiments, and right now, it seems that they were not adequately controlled.

  3. Vy says:

    Good to know. What of cavitation and lightning? The last thing I saw about that was an experiment by F. Cardone et. al many years ago.

    1. Jay Wile says:

      Cardone is still publishing. Here is his latest:
      Certainly, his results are interesting, but I am not sure what they mean. I do know that the Italian government was going to invest serious money in his work, but his detractors got that cancelled.

  4. Jake says:

    This probably doesn’t do anything to the idea that dark matter could accelerate radioactive decay, as the absence of seasonal variation in decay rates doesn’t imply an absence of seasonal variation in dark matter detection rates. That particular seasonal variation could be incredibly small, as it would come from the difference in our velocity relative to the dark matter flow as the earth goes around the sun. All it says is that the difference in apparent dark matter density due to the change in earth’s velocity is too small to observably affect decay rates. Changing decay rates appreciably would require hitting a region of space with a much greater dark matter density.

  5. Greg Gates says:

    I pastor a church in San Jose, CA.
    I recently read your blog and got a lot out of it. We have an usual number of engineers in our church so I this is an important topic for them. I used some of your material in a sermon.
    Please keep up the good work.

    1. Jay Wile says:

      God bless you, pastor!

  6. Francesco says:

    How do we address claims by Christians like Francis Collins, head of the Human Genome Project, who absolutely believe in biological evolution instead of creation because, according to them, what we see in the DNA across different living forms only makes sense in terms of evolution?

    1. Jay Wile says:

      I would say to him, as I have said to other Christian evolutionists who make that argument, that the DNA of organisms falsifies evolution. I have written about this in a few other blog posts (here, here, here, and here). Dr. Hunter also catalogs several ways DNA falsifies evolution.

  7. Francesco says:

    What do you think of Russell Humphreys’s cosmological argument? Do you know of better alternatives?

    1. Jay Wile says:

      Wikipedia’s discussion of his cosmology is not very good. I like his original approach in “Starlight and Time,” but I think Hartnett’s approach is better,

      1. Francesco says:

        Will check it out, thank you.

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