Pioneer Anomaly is no longer anomalous

Thanks to funding from the Planetary Society, of which I am a proud member, the “Pioneer Anomaly” has been definitively resolved. Physics has prevailed over speculation.

Over the past 20 years, some people, including a few scientists, have looked at oddities in the trajectories of the Pioneer 10 and 11 spacecraft and proposed that our understanding of gravity was flawed. Now we have a much more mundane explanation that requires no exotic new theories.

Due to the structure of the spacecraft, they radiate more heat in some directions than others. That produces a very small force that, when added to the gravity of known solar system bodies, leads to exactly the trajectories that have been observed.

It took a lot of detailed sleuthing to get the necessary data, but the result is satisfying, even though it disappoints some who were hoping for a breakthrough that might lead us to resolving some perplexing issues in physics. [See the prologue and concluding sections of Physics: Decade by Decade by Fred Bortz (Twentieth-Century Science set, Facts on File, 2007).]

Details at Bruce Betts’ entry at the Planetary Society’s blog.

4 thoughts on “Pioneer Anomaly is no longer anomalous

  1. This is one of the more fascinating articles i’ve ever read, although it’s fascination for me is part of my own personality.

    I was never very good at calculus because I was mathematically very sloppy. I understood the theory, but I kept making simlpe mathematical errors and always got the wrong answer. But one of the things about calculus – trends over time, trends over a large range of input values – is how little an error it took to create such a large discrepancy in the answer.

    Everybody remembers Jeff Goldblum delivering the line from Jurassic Park about the “butterfly effect”; for many people that shallow dip into science was their first and at least most memorable thought experiment of their whole life. “Oh, a butterfly flaps it’s wings and creates a hurricane” – they don’t even understand it, but they’re fascinated by it. For those of us who read James Gleik’s “Chaos” and knew about Lorenz and his strange attractors, and all the other things mankind has learned about our universe and the math that describes it, that “Butterfly Effect” moment was when we connected the arcane esoteric mathematics we didn’t understand to the world we were standing on that, until that moment we thought we did understand.

    It was a moment that made me appreciate that no matter how much I know, there’s always more to learn, and the more you know, the easier it is to learn more.

    I look at this story – Pioneer 10 and 11 were both launched when I was a young child, and they were the first space probes I remember that brought us the images of the outer planets – the big ones, Jupiter, and Saturn, that held so much fascination for young kids like me.

    And now as a middle-aged adult, it still just delights me to think that those man-made machines are still out there somewhere. For almost my entire life, they’ve been moving at a speed that is unattainable by any vehicle here on Earth, and they’ve never stopped moving throughout that entire time. All the vacations I’ve taken, all the semesters of school, no matter what I was doing that was the focus of my mundane life, Pioneer 10 and 11, have done principally one thing and just kept doing it: Move really fast away from the Earth.

    It was Pioneer that took the “Family Photo” of the planets from the outer limits of the solar system, that gave me, (at least and I assume so many others) a completely new perspective of our place in the Cosmos. Thank you Carl Sagan for the foresight to take that series of photos.

    I was born in 1967, not long before the very first images were ever taken of the Earth itself. Think of the “Earthrise” photo of Apollo 8, or the “Blue Marble” photo of Apollo 17.

    Pioneer gave us the photo that inspired Sagan’s moving essay entitled the Pale Blue Dot.

    And here it is now, a working, practical example of “the butterfly effect”. A miniscule effect of heating – as i understand it, the sun heats the craft and that heat, when it radiates from the craft back out into space, has an effect on it’s tragectory. Measured instantaneously, the effect is so small that it’s not only negligible, but barely even measurable or detectable. But compounded over thirty years or more, it’s effect cannot be ignored.

    There are so many lessons in this one story.

    At least to a guy who thinks a lot, albeit about things that most people think aren’t worthy of their time or consideration. I’m the guy in between the rocket scientists who can make these machines that do such extraordinary things, and the average American who’s attention is measured in nanoseconds and only captured by shiny objects and loud noises.

    I am captivated by the fascination that science provides, (if you care enough just to pay attention and learn what it offers) frustrated that I wasn’t better at the math so that I could have made my career from investigating and building upon such curious matters.

    A little push, applied over forty years – each instant of it so subtle that it can barely be comprehended, nevermind measured – and that slight effect compounded over decades is ultimately is so significant it can’t be ignored.

    That’s deep stuff.

    I often have arguments with religious people who belittle science; they disparage it and only talk pejoratively about all the things that go wrong, or all the unforseen consequences that science brings. And yet those same people are comfortably immersed in – completely dependent on – so many other scientific benefits that they comfortably ignore, if they ever even knew about in the first place.

    All those things are made possible by the kind of minds that have the capacity and the tenacity to investigate something like “the Pioneer Anomaly”.

    This is a great article, I’ll be telling this story for years to people who will roll their eyes at me and say I’m nuts to be interested in something so silly.

    But “silly” is in the mind of those pondering it.

    In my mind, this is a fascinating tale of curiosity, committment, and validation of the scientific method.

    The answers are out there for those who don’t stop looking.

    I’ve never read this blog before. Fred Bortz, whoever you are, thank you for writing this.

  2. It wasn’t pioneer that took the family photo, it was Voyager.

    see what I mean about being sloppy with a short attention span?

    Sorry about that.

  3. In no way do I belittle science! It is an investigation of a fascinating world of complexity far beyond what has yet been discovered. It is short-sighted to belittle all “religious” people because of the fear and short-sightedness of a few. It is not in science that we disagree but in philosophy. I am a Christian ever discovering the wonders of our world and worlds beyond our own, and these are evidence of a Creator whose intelligence and design is evident in what He has created. I value and esteem scientists who open windows and doors for me. The facts will eventually reveal what is True, and that may be beyond our short lives which do not enter oblivion just because our bodies die. That claim is merely a claim till we come to know it for ourselves. In the mean time, it would be advisable to avoid “straw man” logical fallacies to denigrate or to belittle science-honoring fellow human beings with whose philosophies we disagree.

    • Heather, “Information sponge” is not belittling you or disparaging all religious people. S/he is speaking of some particular religious people that s/he has interacted with.

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