# Radioactivite decay variance due to distance from the sun?

1. ### Whyisthat21

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Hello! I'm not entirely sure this is very "scientific", but I have an idea that I would like some feedback on. I remember reading an article related to radioactive decay varying with the rotation and distance from the sun on Phys.org a few years back (http://phys.org/news202456660.html) and was pretty intrigued by the idea. They state the fluctuation is roughly a "tenth of a percent", which is pretty uneventful in the large scale of daily life. In a seemingly unrelated story about the Pioneer Anomaly (http://phys.org/news/2012-07-source-anomaly.html) I had a theory that could possibly be tested. Perhaps radioactivity is more variable than we understand since we have a pretty steady distance from the sun, and also are under the influence of the heliosphere at all times. My question or idea or hypothesis is: could we use the data from either the temperature, power output, or maybe the deceleration effect of the radioactive thermoelectric generators on board the viking spacecraft(s) to calculate any statistically significant fluctuations in the decay rates near the edge of the solar system? And would it be useful? Just a thought I've had for a while; I thought maybe someone had some input or solid reasoning that will get this out of my 'hypothesis box'.

18,156
Staff Emeritus
This was discussed here when it first came out.

At the time, I said:

I still believe that. The fact that in 6 years nobody has been able to duplicate the effect is also strong evidence that this was another Fischbach Fluke.

As for Pioneer and Voyager, this would predict a ~5% effect in the power output. I suspect, but do not know, that this would be detectable, particularly since there are four probes.

### Staff: Mentor

They would need a poor power monitoring if 5% more or less energy would not be seen in some way. As an example, in 2008, NASA quoted the electric power as 285W for Voyager 1 and 287W for Voyager 2. They don't write it explicitly, but that looks like they see a difference between the two values so at least the electric power is known to 1% or better.

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