Dec 082012
 

One of my favorite photographs ever, in fact one that I even use on my Facebook timeline page as a background image, was taken by a certain Bill Anders when he was flying almost 400,000 km from the Earth. Anders was one of the first three members of our species who flew to another celestial body (albeit without landing on its surface; that came a bit later.)

Yesterday, I read a very interesting article about Anders, both his trip on board Apollo 8 and his life afterwards. The article also touched upon the topic of religion.

The message radioed back by the crew of Apollo 8 is probably the most memorable Christmas message ever uttered by humans. (Or maybe I am biased.) And yes, it starts with the words from Genesis, but I always viewed it the way it was presumably intended: as an expression of awe, not as religious propaganda.

The curious thing, as mentioned in the article, is that it was this trip around the Moon that changed the traditional Christian viewpoint of Anders about Earthlings created by a God in his own image.

“When I looked back and saw that tiny Earth, it snapped my world view,” Anders is quoted as saying. “Are we really that special? I don’t think so.”

Well, this pretty much sums up why I am an atheist. I’d like to believe that it’s not hubris; it’s humility.

 Posted by at 10:55 am
Nov 302012
 

An article we wrote with Slava Turyshev about the Pioneer anomaly and its resolution, at the request of IEEE Spectrum, is now available online.

It was an interesting experience, working with a professional science journalist and her team. I have to admit that I did not previously appreciate the level of professionalism that is behind such a “members only” magazine.

 Posted by at 3:22 pm
Oct 312012
 

I began this blog of mine a little over ten years ago, although it took a bit longer than that before I was able to bring myself around and actually call it a “blog”. (I originally called this a “Day Book”, a term I borrowed from Jerry Pournelle.)

In 2002, I wrote about Brian Herbert’s prequels to his father’s, Frank Herbert’s, Dune series of books.

In 2003, I introduced my Halloween cat. I wrote about Moscow schools banning Halloween. I wrote about electronic voting in Ontario using a Linux-based system, and about a stray cat in our neighborhood that may have been killed by the Humane Society.

In 2004, I wrote about Halloween cats (including our very first cat, Marzipan and his Halloween dance) and about the shutdown of Mirabel airport.

In 2005, I was wondering if Condoleeza Rice, with her glowing eyes, might actually be a Goa’uld System Lord from Stargate SG-1.

In 2006, it was time to celebrate NASA’s decision to reinstate the final Hubble repair mission after all.

In 2007, I was speculating about ant colonies and group consciousness.

In 2008, I had nothing to say. Fittingly, this was the last time I used my old, homebrew blogging engine.

After switching to WordPress, in 2009 I complained about daylight savings time. I still think that switching to daylight savings time is a ridiculous gimmick that does far more harm than good in a post-industrial society.

In 2010, I was complaining about snow in October.

2011 was a scary Halloween indeed: it was on that very day that the world’s population supposedly reached 7 billion. Also on that day, the debt-to-GDP ratio of the United States reached 100%. And there was a major snowstorm in New England.

And here comes 2012, the scariest Halloween yet since I started blogging: a good one third of Manhattan is still in darkness, large sections of New Jersey are ruined, millions are still without power, scores are dead, and the remnants of Sandy are heading in our direction, bringing rain, cold, perhaps even some snow.

But for what it’s worth, Happy Halloween to all!

 Posted by at 12:07 pm
Sep 272012
 

Earlier this morning, I came across the following headline on Google News: “Fewer crashes when docs report bad drivers, study finds“.

The headline almost made sense. Yes, bad drivers cause crashes, indeed the main reason why modern operating systems crash these days is bad third-party drivers. So being able to identify and report a bad driver kind of makes sense, but how would you do that? And what does it have to do with your docs? Did the author mean perhaps that a document, say, an HTML page, could display a warning about a bad driver instead of invoking the driver (e.g., to display video) and risk crashing the browser or the computer?

Then, about three tenths of a second later, I realized that the headline was about road accidents and medical doctors.

 Posted by at 5:40 pm
Sep 272012
 

Once again, I was doing something dangerous: despite being a programmer, I chose to carry not just a screwdriver but also some power tools.

Two weeks ago, I had a plumbing crew remove our old bathtub. It was way overdue:

It took them no more than a couple of hours to reduce the bathtub to this:

And by mid-afternoon, they were done. The new bathtub was installed. Actually, let me emphasize: ONLY the new bathtub was installed:

From this point on, I was on my own. It was by choice: I dislike having workmen in my house and in any case, these are skills that, I think, are well worth learning.

Having never done tiles (or for that matter, sheet rock) before, I was taking things slowly. (Hey, I am also just a few months shy of fifty, somewhat overweight, and I usually spend my days in an armchair sitting in front of a computer.) Even so, a few days later, I was done with all the preliminary work: notably, the installation of tile backer drywall:

The plastic sheets were put in there so that we could use the bathroom even while it was still under construction.

Next came the tiles. The tricky bit (for me anyway) was to cut tiles around the faucet and other fixtures. I was able to cut pretty decent holes using a tile cutter bit in my “Roto-ZIP” tool:

And thus it came to be that a little less than two weeks after the plumbers left, the tiling was done:

There was, of course, still more work to do. First, I had to wait a few days for the adhesive to set before grouting the tiles. Once I completed the grouting successfully, I had to wait another few days before I could spray the new grout with sealant. It was only at this point, namely today, that I sealed the edges of the tile using silicone. Finally, once the fixtures were reattached, the job was at last done:

Needless to say, I am mighty proud of myself. In fact, I’ll probably be insufferably proud for the next few days (that is, unless the tiles start popping off, in which case my insufferable pride will rapidly turn into an overwhelming sense of embarrassment.) There is still a little bit of cleaning up to do, and eventually, repaired bits of wall around the tiles will need to be repainted. I may apply a bit of paint for protection, but the real paintjob will have to wait; I am considering replacing the vanity (the sink definitely needs to be replaced) and I am also considering replacing the floor tiles, which are old and have developed a few minor cracks over the years.

But not this year. For now, I prefer to return to my regularly scheduled programming job and put down my screwdriver.

Phew!

 Posted by at 5:32 pm
Sep 132012
 

Busy celebrating our 20th wedding anniversary yesterday, I forgot that there was another important anniversary on September 12: it was fifty years ago yesterday that a certain John F. Kennedy uttered the words, “We choose to go to the Moon. We choose to go to the Moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win, and the others, too.” And with those words, an astonishing sequence of events took place, and before the 1960s came to an end, two Americans indeed landed on the Moon… a technological feat the like of which the world has not seen since 1972, when the last of the Apollo Moon shots took place.

 Posted by at 7:52 am
Sep 122012
 

My wife and I have been married for exactly twenty years today. I hope the next twenty years will be at least as much fun for both of us as the first.

 Posted by at 9:49 pm
Sep 122012
 

That the main function of the post office is to deliver letters may be obvious to many, but apparently it wasn’t obvious to a postal employee today when my wife tried to mail an oversize letter to Hungary. It would be about $30 surface, or $60 air mail, said the young employee to my wife who was so surprised at first, she was unable to respond. Thankfully, a senior clerk overheard the conversation and eventually came to her colleague’s rescue, explaining to her that a letter is not a parcel. Actual cost? $4.20, for a letter weighing between 50 and 100 grams. Though I am seriously beginning to wonder if at least half that price is due to the inefficiencies of inept postal employees…

 Posted by at 5:26 pm
Sep 062012
 

Nature had a nice editorial a few days ago about the Pioneer Anomaly and our research, titled “…and farewell to the Pioneer anomaly” (so titled because in the print edition, it is right below the obituary,  titled “Farewell to a pioneer”, of Bernard Lovell, builder of what was at the time the world’s largest steerable radio telescope at Jodrell Bank).

Farewell, yes, though I still hope that we will have the wherewithal to publish a longer article in which we provide the details that did not fit onto the pages of Physical Review Letters. We ought to update our review paper in Living Reviews in Relativity, too. We need to prepare for the release of the data used in our analysis. And, if possible, I’d like to spend time tackling some of the open questions we discuss near the end of our last paper, such as analyzing the spin behavior of the two spacecraft or making use of DSN signal strength measurements to improve the trajectory solution.

First things first, though; right now, my priorities are to a) earn money (which means doing things that I actually get paid for, not Pioneer) and b) get ready to have our upstairs bathtub replaced (the workmen will be here Monday morning), after which I plan to do the wall tiles myself (with fingers firmly crossed in the hope that I won’t mess it up too badly.)

Yes, sometimes such mundane things must take priority.

 Posted by at 11:26 am
Aug 102012
 

It was over thirty years ago, back in 1979-1980, that I first earned money from a software development contract. My first assignment? Aircraft simulation, specifically tabulating the minimum safe take-off distance of TU-154 aircraft at Budapest airport under various loads and weather conditions.

Alas, the Hungarian national airline, MALÉV, is no more. But as of today, I became the proud owner of a MALÉV TU-154 B-2, with the original MALÉV markings.

No, not the real thing, I’m not that rich (and even if I were that rich, I’d not be spending my money on obsolete Russian aircraft), just a beautiful diecast model. Still, it’s a nice reminder.

 Posted by at 6:15 pm
Jul 202012
 

I completely forgot: four days ago was the 25th anniversary of my arrival in Canada as a landed immigrant. I never had a reason to regret my choice… in fact, politics of the day notwithstanding, I appreciate this country more than ever.

 Posted by at 12:47 pm
Jul 202012
 

I just came across a photograph of a building that looks like one of the abandoned edifices in the ghost city of Prypiat, right next to the Chernobyl nuclear power station. Indeed, the picture appeared in a Facebook blog that features many pictures from Prypiat… but this wasn’t one of them.

Instead, the picture was taken in Hungary, on the south shore of Lake Balaton. The building is an abandoned hotel that before the collapse of Communism served as a resort, owned by the Hungarian Industrial Association. I spent nights at that resort. In particular, I spent nights in this very building shown in the picture.

What I found most striking is that the building looks exactly the same as it did 30-odd years ago (except for the decay, of course). It was apparently never modernized. Never really renovated. Presumably, it was privatized some time after 1989, served as a hotel for a while, and then it was abandoned… but it still looks exactly the same (insofar as I can remember) as it did back in the late 1970s.

I guess I now have a better appreciation of how residents of Prypiat feel when they come across present-day photographs of their once proud town. It is an eerie feeling.

 Posted by at 10:42 am
Jul 182012
 

Having been told by a friend that suddenly, there is a spate of articles online about the Pioneer anomaly, I was ready to curse journalists once I came across the words: “a programmer in Canada, Viktor Toth, heard about the effort and contacted Turyshev. He helped Turyshev create a program …”.

To be clear: I didn’t contact Slava; Slava contacted me. I didn’t “help create a program”; I was already done creating a program (which is why Slava contacted me). And that was the state of things back in 2005. What about all the work that I have done since, in the last seven years? Like developing a crude and then a more refined thermal model, independently developing precision orbit determination code to confirm the existence of the anomaly, collaborating with Slava on several papers including a monster review paper published by Living Reviews in Relativity, helping shape and direct the research that arrived at the present results, and drafting significant chunks of the final two papers that appeared in Physical Review Letters?

But then it turns out that journalists are blameless for a change. They didn’t invent a story out of thin air. They just copied the words from a NASA JPL press release.

And I am still trying to decide if I should feel honored or insulted. But then I am reminding myself that feeling insulted is rarely productive. So I’ll go with feeling honored instead. Having my contribution acknowledged by JPL is an honor, even if they didn’t get the details right.

 Posted by at 4:15 pm
Jul 152012
 

An anniversary I completely forgot about (no, not my wedding anniversary; I’d never forget that!) It was in May 2002, just a little over ten years ago, that I began my Day Book, a term I borrowed from Jerry Pournelle as the word “(we)blog” was not invented yet.

It took me a while to get used to the word “blog”. To be honest, I hated it at first. Later, I told myself to accept the inevitable. Society changes. Culture changes. Language changes. I can either go with the flow or choose to be left behind, prematurely condemning myself to being a grumpy old man. And it’s way too early for that.

 Posted by at 1:06 pm
Jul 102012
 

I once had a profound thought, years ago.

I realized that many people think that knowing the name of something is the same as understanding that thing. “What’s that?” they ask, and when you reply, “Oh, that’s just the blinking wanker from a thermonuclear quantum generator,” they nod deeply and thank you with the words, “I understand”. (Presumably these are the same people who, when they ask “How does this computer work?”, do not actually mean that they are looking for an explanation of Neumann machines, digital electronics, modern microprocessor technology, memory management principles, hardware virtualization techniques and whatnot; they were really just looking for the ON switch. Such people form an alarming majority… but it took me many frustrating years to learn this.)

I am not sure how to feel now, having just come across a short interview piece with the late physicist Richard Feynman, who is talking about the same topic. The piece is even titled “Knowing the name of something“. I am certainly reassurred that a mind such as Feynman’s had the same thought that I did. I am also disappointed that my profound thought is not so original after all. But I feel I should really be encouraged: perhaps this is just a sign that the same thought might be occurring to many other people, and that might make the world a better place. Who knows… in a big Universe, anything can happen!

 

 Posted by at 9:05 am
Jun 152012
 

Our latest Pioneer paper, in which we discuss the results from the Pioneer thermal model and its incorporation into the orbital analysis (the conclusion being that no significant anomalous acceleration remains once thermal radiation is properly accounted for) made it to the cover of Physical Review Letters. I am very grateful that I was given the opportunity to participate in this research, and I am very proud of this work and our results.

 Posted by at 11:35 am
Apr 122012
 

Our second short paper has been accepted for publication in Physical Review Letters.

I have been involved with Pioneer 10 and 11 in some fashion since about 2002, when I first began corresponding with Larry Kellogg about the possibility of resurrecting the telemetry data set. It is thanks the Larry’s stamina and conscientiousness that the data set survived.

I have been involved actively in the research of the Pioneer anomaly since 2005. Seven years! Hard to believe.

This widely reported anomaly concerns the fact that when the orbits of Pioneer 10 and 11 are accurately modeled, a discrepancy exists between the modeled and measured frequency of the radio signal. This discrepancy can be resolved by assuming an unknown force that pushes Pioneer 10 an 11 towards the Earth or the Sun (from that far away, these two directions nearly coincide and cannot really be told apart.)

One purpose of our investigation was to find out the magnitude of the force that arises as the spacecraft radiates different amounts of heat in different directions. This is the concept of a photon rocket. A ray of light carries momentum. Hard as it may appear to believe at first, when you hold a flashlight in your hands and turn it on, the flashlight will push your hand backwards by a tiny force. (How tiny? If it is a 1 W bulb that is perfectly efficient and perfectly focused, the force will be equivalent to about one third of one millionth of a gram of weight.)

On Pioneer 10 and 11, we have two main heat sources. First, there is electrical heat: all the instruments on board use about 100 W of electricity, most of which is converted into heat. Second, electricity is produced, very inefficiently, by a set of four radioisotope thermoelectric generators (RTGs); these produce more than 2 kW of waste heat. All this heat has to go somewhere, and most of this heat will be dissipated preferably in one direction, behind the spacecraft’s large dish antenna, which is always pointed towards the Earth.

The controversial question was, how much? How efficiently is this heat converted into force?

I first constructed a viable thermal model for Pioneer 10 back in 2006. I presented results from custom ray-tracing code at the Pioneer Explorer Collaboration meeting at the International Space Science Institute in Bern, Switzerland in February 2007:

With this, I confirmed what has already been suspected by others—notably, Katz (Phys. Rev. Letters 83:9, 1892, 1999); Murphy (Phys. Rev. Letters 83:9, 1890, 1999); and Scheffer (Phys. Rev. D, 67:8, 084021, 2003)—that the magnitude of the thermal recoil force is indeed comparable to the anomalous acceleration. Moreover, I established that the thermal recoil force is very accurately described as a simple linear combination of heat from two heat sources: electrical heat and heat from the RTGs. The thermal acceleration \(a\) is, in fact

$$a=\frac{1}{mc}(\eta_{\rm rtg}P_{\rm rtg} + \eta_{\rm elec}P_{\rm elec}),$$

where \(c\simeq 300,000~{\rm km/s}\) is the speed of light, \(m\simeq 250~{\rm kg}\) is the mass of the spacecraft, \(P_{\rm rtg}\sim 2~{\rm kW}\) and \(P_{\rm elec}\sim 100~\rm {W}\) are the RTG heat and electrical heat, respectively, and \(\eta_{\rm rtg}\) and \(\eta_{\rm elec}\) are “efficiency factors”.

This simple force model is very useful because it can be incorporated directly into the orbital model of the spacecraft.

In the years since, the group led by Gary Kinsella constructed a very thorough and comprehensive model of the Pioneer spacecraft, using the same software tools (not to mention considerable expertise) that they use for “live” spacecraft. With this model, they were able to predict the thermal recoil force with the greatest accuracy possible, at different points along the trajectory of the spacecraft. The result can be compared directly to the acceleration that is “measured”; i.e., the acceleration that is needed to model the radio signal accurately:

In this plot, the step-function like curve (thick line) is the acceleration deduced from the radio signal frequency. The data points with vertical error bars represent the recoil force calculated from the thermal model. They are rather close. The relatively large error bars are due primarily to the fact that we simply don’t know what happened to the white paint that coated the RTGs. These were hot (the RTGs were sizzling hot even in deep space) and subjected to solar radiation (ultraviolet light and charged particles) so the properties of the paint may have changed significantly over time… we just don’t know how. The lower part of the plot shows just how well the radio signal is modeled; the average residual is less than 5 mHz. The actual frequency of the radio signal is 2 GHz, so this represents a modeling accuracy of less than one part in 100 billion, over the course of nearly 20 years.

In terms of the above-mentioned efficiency factors, the model of Gary’s group yielded \(\eta_{\rm rtg}=0.0104\) and \(\eta_{\rm elec}=0.406\).

But then, as I said, we also incorporated the thermal recoil force directly into the Doppler analysis that was carried out by Jordan Ellis. Jordan found best-fit residuals at \(\eta_{\rm rtg}=0.0144\) and \(\eta_{\rm elec}=0.480\). These are somewhat larger than the values from the thermal model. But how much larger?

We found that the best way to answer this question was to plot the two results in the parameter space defined by these two efficiency factors:

The dashed ellipse here represents the estimates from the thermal model and their associated uncertainty. The ellipse is elongated horizontally, because the largest source of uncertainty, the degradation of RTG paint, affects only the \(\eta_{\rm rtg}\) factor.

The dotted ellipse represents the estimates from radio signal measurements. The formal error of these estimates is very small (the error ellipse would be invisibly tiny). These formal errors, however, are calculated by assuming that the error in every one of the tens of thousands of Doppler measurements arises independently. In reality, this is not the case: the Doppler measurements are insanely accurate, any errors that occur are a result of systematic mismodeling, e.g., caused by our inadequate knowledge of the solar system. This inflates the error ellipse and that is what was shown in this plot.

Looking at this plot was what allowed us to close our analysis with the words, “We therefore conclude that at the present level of our knowledge of the Pioneer 10 spacecraft and its trajectory, no statistically significant acceleration anomaly exists.”

Are there any caveats? Not really, I don’t think, but there are still some unexplored questions. Applying this research to Pioneer 11 (I expect no surprises there, but we have not done this in a systematic fashion). Modeling the spin rate change of the two spacecraft. Making use of radio signal strength measurements, which can give us clues about the precise orientation of the spacecraft. Testing the paint that was used on the RTGs in a thermal vacuum chamber. Accounting for outgassing. These are all interesting issues but it is quite unlikely that they will alter our main conclusion.

On several occasions when I gave talks about Pioneer, I used a slide that said, in big friendly letters,

PIONEER 10/11 ARE THE MOST PRECISELY NAVIGATED DEEP SPACE CRAFT TO DATE.

And they confirmed the predictions of Newton and Einstein, with spectacular accuracy, by measuring the gravitational field of the Sun in situ, all the way up to about about 70 astronomical units (the distance of the Earth from the Sun).

 Posted by at 11:10 am
Apr 082012
 

I have no delusions about my abilities as a graphic artist, but hey, it’s from the heart. Happy Easter, everyone!

As to why we choose to celebrate the gruesome death on the cross and subsequent resurrection of a young man some 2,000 years ago, one whose sole crime was that he was preaching love and understanding among neighbors, with bunny rabbits laying gaudy-colored eggs and such nonsense, I have no idea. But then, I am just the clueless atheist here, so what do I know?

I only wish more people actually listened to that young man’s message, instead of choosing hatred and violence. The world would indeed be a better place.

 Posted by at 9:37 am
Mar 012012
 

Maxima is an open-source computer algebra system (CAS) and a damn good one at that if I may say so myself, being one of Maxima’s developers.

Among other things, Maxima has top-notch tensor algebra capabilities, which can be used, among other things, to work with Lagrangian field theories.

This week, I am pleased to report, SourgeForge chose Maxima as one of the featured open-source projects on their front page. No, it won’t make us rich and famous (not even rich or famous) but it is nice to be recognized.

 Posted by at 9:35 am