Discovery News | August 25, 2010
By Ian O'Neill

When probing the deepest reaches of the Cosmos or magnifying our understanding of the quantum world, a whole host of mysteries present themselves. This is to be expected when pushing our knowledge of the Universe to the limit.

But what if a well-known -- and apparently constant -- characteristic of matter starts behaving mysteriously?

This is exactly what has been noticed in recent years; the decay rates of radioactive elements are changing. This is especially mysterious as we are talking about elements with "constant" decay rates -- these values aren't supposed to change. School textbooks teach us this from an early age.

This is the conclusion that researchers from Stanford and Purdue University have arrived at, but the only explanation they have is even weirder than the phenomenon itself: The sun might be emitting a previously unknown particle that is meddling with the decay rates of matter. Or, at the very least, we are seeing some new physics.

Many fields of science depend on measuring constant decay rates. For example, to accurately date ancient artifacts, archaeologists measure the quantity of carbon-14 found inside organic samples at dig sites. This is a technique known as carbon dating.

Carbon-14 has a very defined half-life of 5730 years; i.e. it takes 5,730 years for half of a sample of carbon-14 to radioactively decay into stable nitrogen-14. Through spectroscopic analysis of the ancient organic sample, by finding out what proportion of carbon-14 remains, we can accurately calculate how old it is.

But as you can see, carbon dating makes one huge assumption: radioactive decay rates remain constant and always have been constant. If this new finding is proven to be correct, even if the impact is small, it will throw the science community into a spin.

Interestingly, researchers at Purdue first noticed something awry when they were using radioactive samples for random number generation. Each decay event occurs randomly (hence the white noise you'd hear from a Geiger counter), so radioactive samples provide a non-biased random number generator.

However, when they compared their measurements with other scientists' work, the values of the published decay rates were not the same. In fact, after further research they found that not only were they not constant, but they'd vary with the seasons. Decay rates would slightly decrease during the summer and increase during the winter.
 

Experimental error and environmental conditions have all been ruled out -- the decay rates are changing throughout the year in a predictable pattern. And there seems to be only one answer.

As the Earth is closer to the sun during the winter months in the Northern Hemisphere (our planet's orbit is slightly eccentric, or elongated), could the sun be influencing decay rates?

In another moment of weirdness, Purdue nuclear engineer Jere Jenkins noticed an inexplicable drop in the decay rate of manganese-54 when he was testing it one night in 2006. It so happened that this drop occurred just over a day before a large flare erupted on the sun.

Did the sun somehow communicate with the manganese-54 sample? If it did, something from the sun would have had to travel through the Earth (as the sample was on the far side of our planet from the sun at the time) unhindered.

The sun link was made even stronger when Peter Sturrock, Stanford professor emeritus of applied physics, suggested that the Purdue scientists look for other recurring patterns in decay rates. As an expert of the inner workings of the sun, Sturrock had a hunch that solar neutrinos might hold the key to this mystery.

Sure enough, the researchers noticed the decay rates vary repeatedly every 33 days -- a period of time that matches the rotational period of the core of the sun. The solar core is the source of solar neutrinos.

It may all sound rather circumstantial, but these threads of evidence appear to lead to a common source of the radioactive decay rate variation. But there's a huge problem with speculation that solar neutrinos could impact decay rates on Earth: neutrinos aren't supposed to work like that.

Neutrinos, born from the nuclear processes in the core of the sun, are ghostly particles. They can literally pass through the Earth unhindered as they so weakly interact. How could such a quantum welterweight have any measurable impact on radioactive samples in the lab? 

In short, nobody knows.

If neutrinos are the culprits, it means we are falling terribly short of understanding the true nature of these subatomic particles. But if (and this is a big if) neutrinos aren't to blame, is the sun generating an as-yet-to-be- discovered particle?

If either case is true, we'll have to go back and re-write those textbooks.

Source: Stanford University