99 percent perspiration solves mystery of Pioneer Anomaly
Photo courtesy of NASA website.

I was just a kid when Pioneer 10 and 11 were launched to explore our solar system.  Now, I have children older than I was back in '73, and these probes have flown the asteroid belt, checked out Jupiter and Saturn, and are on their way out of the solar system.  However, they've been slowing down, and that's a mystery that has taken nearly a decade to solve.

NASA scientists first noticed the slowdown in the 80s, but passed it off as "a transient phenomenon resulting from dribbles of propellant left in the probe's lines, according to researchers." (Space News, July 23, 2012).  However, the craft kept on slowing, albeit slightly, and in 1998, they no longer expected the problem to stop.  Certainly, they couldn't do anything about it, but it did leave a question:  What was slowing them down?

They dubbed it the "Pioneer Anomaly" and went to far as to suggest that they were dealing with a new type of physics that contradicted Einstein's General Theory of Relativity.  how exciting would that be?

In 2004, Slava Turyshev of Jet Propulsion Laboratory decided to study the phenomenon.  He and his colleagues searched through the Pioneer probes' telemetry--43 gigabytes of information, much of it on on magnetic tapes that had to be converted as well as digitized files.  Eight years later, they published their discovery in Physical Review Letters.

It was heat.

Yep, that little bit of heat caused by electricity running through the systems of the Pioneer probes actually pushed back on the probes, causing them to slow.  Space News quotes Turyshev with saying it was like the photons of your car's headlights pushing back on your car. Apparently, however, when dealing with the speeds of the spacecraft and the distances and environment of space, that can have a noticeable, albeit very subtle, effect.

How mundane is this--and yet so awesome!  First, there's the simple idea that something so basic can have such a profound effect that we might even doubt General Relativity.  How much we don't know about the practicalities of space travel!

Secondly, think about all the work, all the minutia, data crunching, file conversion, etc. that went into figuring out something that in hindsight seems so ordinary.  Eight years!  I don't know about you, but I can get tired and bored just trying to find a coding problem on my website, and these guys went through 53 years' worth of data between the two probes.

My hat's off to you, Dr. Turyshev, and to all who worked so diligently on this mystery.  Next time I turn on my headlights, I'll think of you.

For more reading:

About the discovery:
About Pioneer 10 and 11:

**BTW, my apologies for not posting last Tuesday's space studies.  I'll discuss Doppler effects with the next lesson on Tuesday.

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