Oct 112013
 

Reader’s Digest recently conducted an interesting experiment: they “lost” 12 wallets, filled with about $50 worth of cash and sufficient documentation to locate the owner, in 16 cities around the world. The result: Finns in Helsinki are the most honest with 11 of the 12 wallets returned, whereas in Lisbon, Portugal, the sole wallet that was returned was, in fact, found by a visiting Dutch couple. Finns needless to say, are rejoicing: “we don’t even run red lights,” boasted a Helsinki resident.

So what can we conclude from this interesting experiment? Perhaps shockingly, almost nothing.

This becomes evident if I plot a histogram with the number of wallets returned, and overlay on it a binomial distribution for a probability of 46.875% (which corresponds to the total number of wallets returned, 90 out of 192), I get a curve that is matched very closely by the histogram. Unsurprisingly, there will be a certain probability that in a given city, 1, 2, 3, etc. wallets are returned; and the results of Reader’s Digest match this prediction closely.

So there is no reason for Finns to rejoice or for the Portuguese to feel shame. It’s all just blind luck, after all. And the only valid conclusion we can draw from this experiment is that people are just as likely to be decent folks in Lisbon as in Helsinki.

But how do you explain this to a lay audience? More importantly, how do you prevent a political demagogue from drawing false or unwarranted conclusions from the data?

 Posted by at 9:40 pm
Oct 112013
 

Is this a worthy do-it-yourself neuroscience experiment, or an example of a technology gone berserk, foreshadowing a bleak future?

A US company is planning to ship $99 kits this fall, allowing anyone to turn a cockroach into a remote controlled cyborg. Educational? Or more like the stuff of bad dreams?

For me, it’s the latter. Perhaps it doesn’t help that I am halfway through reading Margaret Atwood’s The Year of the Flood, sequel to Oryx and Crake, a dystopian science fiction novel set in a bleak future in which humanity destroys itself through the reckless use of biotech and related technologies.

A cockroach may not be a beloved animal. Its nervous system may be too small, too simple for it to feel real pain. Nonetheless, I feel there is something deeply disturbing and fundamentally unethical about the idea of turning a living animal into a remote control toy.

To put it more simply: it creeps the hell out of me.

 Posted by at 11:49 am
Sep 272013
 

It is now formally official: global surface temperatures did not increase significantly in the past 15 years or so.

But if skeptics conclude that this is it, the smoking gun that proves that all climate science is hogwash, they better think again. When we look closely, the plots reveal something a lot more interesting.

For starters… this is not the first time global temperatures stagnated or even decreased somewhat since the start of recordkeeping. There is a roughly 20-year period centered around 1950 or so, and another, even longer period centered roughly around 1890. This looks in fact like evidence that there may be something to the idea of a 60-year climate cycle. However, the alarming bit is this: every time the cycle peaks, temperatures are higher than in the previous cycle.

The just released IPCC Summary for Policymakers makes no mention of this cycle but it does offer an explanation for the observed stagnating temperatures. These are probably a result of volcanic activity, they tell us, the solar cycle, and perhaps mismodeling the effects of greenhouse gases and aerosols, but they are not exactly sure.

And certainty is characterized with words like “high confidence,” “medium confidence” and such, with no definitions given. These will be supplied, supposedly, in the technical report that will be released on Monday. Nonetheless, the statement that “Probabilistic estimates […] are based on statistical analysis of observations or model results, or both, and expert judgment” [emphasis mine] does not fill me with confidence, if you will pardon the pun.

In fact, I feel compelled to compare this to the various reports and releases issued by the LHC in recent years about the Higgs boson. There was no “expert judgment”. There were objective statistical analysis methods and procedures that were thoroughly documented (even though they were often difficult to comprehend, due to their sheer complexity.) There were objective standards for claiming a discovery.

Given the extreme political sensitivity of the topic, I think the IPCC should adopt similar or even more stringent standards of analysis as the LHC. Do away with “expert judgment” and use instead proper statistical tools to establish the likelihood of specific climate models in the light of the gathered data. And if the models do not work, e.g., if they failed to predict stagnating temperatures, the right thing to do is say that this is so; there is no need for “expert judgment”. Just state the facts.

 Posted by at 10:45 pm
Sep 272013
 

I’ve been hesitant to write about this, as skeptics will already have plenty to gripe about, I don’t need to pile on. And I swear I am not looking for excuses to bash the IPCC, not to mention that I have little sympathy or patience for skeptics who believe that an entire body of science is just one huge scam to make Al Gore and his buddies rich.

But… I was very disappointed to see plots in the latest IPCC “Summary for Policymakers” report that appear unnecessarily manipulative.

Wikipedia describes these as truncated or “gee-whiz” graphs: graphs in which the vertical axis does not start at zero. This can dramatically change the appearance of a plot, making small variations appear much larger than they really are.

To be clear, the use of truncated plots is often legitimate. Perhaps the plot compares two quantities that are of a similar magnitude. Perhaps the plot shows a quantity the absolute magnitude of which is irrelevant. Perhaps the quantity is such that “0” has no special meaning or it is not a natural start of the range (e.g., pH, temperature in Centigrade).

But in other cases, this practice can be viewed as misleading, intellectually dishonest (for instance, it is common for financial companies to manipulate plots this way to make their market performance appear more impressive than it really is) or outright fraudulent.

So here we are, the 2013 IPCC report’s summary for policymakers has been released in draft form, and what do I see in it? Several key plots that have been presented in truncated “gee-whiz” form, despite the fact that the quantities they represent are such that their absolute magnitudes are relevant, that their variability must be measured against their absolute magnitudes, and where zero is a natural start of the range.

I am presenting the original plots on the left and my crudely “untruncated” versions on the right:

This is not kosher, especially in a document that is intended for consumption by a lay audience who may not have the scientific education to spot such subtleties.

The document is still labeled a draft, with copy editing in particular yet to take place. Here’s to hoping that these plots (and any similar plots that may appear in the main report) are corrected before publication, to avoid the impression of trying to exaggerate the case for climate change. Scientists should be presenting the science objectively and leave the manipulation, even inadvertent manipulation, to politicians.

 Posted by at 10:22 pm
Sep 202013
 

Last week, it was all over the news: Voyager 1 has left the solar system.

Except that it really didn’t. Voyager 1’s trajectory is, and will continue to be, dominated by the Sun’s gravity for thousands of years. Voyager 1 is significantly closer to the Sun than Sedna (one of the icy dwarfs in the outer solar system) at aphelion. And then there is the hypothesized Oort cloud, a spherical cloud of planetesimals roughly a light year from the Sun. Voyager 1 will take thousands of years to travel that distance.

Of course, Voyager 1 is way outside the orbit of the outermost planet, Neptune. But that happened decades ago, back in the 1980s. By 1990, Voyager 1 was far enough from the Sun to be able to take its famous “family portrait”, a mosaic that covered six of the eight planets (Mars was too faint, while Mercury was too close to the Sun.)

So what exactly happened this month? Well, Voyager 1 crossed the heliopause, the boundary where the solar wind collides with the interstellar medium. It is also the location where magnetic fields are no longer dominated by the Sun.

So in this sense, Voyager 1 has indeed crossed into the interstellar medium. The particles its instruments sample are the particles found in interstellar space, not particles emitted by the Sun.

So it is a significant milestone, but it is somewhat misleading to suggest that “Voyager 1 has left the solar system”, which we heard so many times in the past several days.

 Posted by at 4:40 pm
Sep 202013
 

Grote_Antenna_WheatonThe world’s first parabolic radio telescope was, astonishingly, built in someone’s back yard.

I am reading about the radio telescope of American amateur radio enthusiast and amateur astronomer Grote Reber.

In 1937, Reber built a 9-meter parabolic reflector in his family’s back yard.

Reber was the first to make a systematic survey of the radio sky, not only confirming Jansky’s earlier, pioneering discovery of radio waves from the Milky Way but also discovering radio sources such as Cygnus X-1 and Cassiopeia A.

grote5

For nearly a decade, Reber was the only person in the world doing radio astronomy.

Reber had a long life. He spent his final years in Tasmania, one of the few places on Earth where occasionally, very low frequency radio waves penetrate the ionosphere and are detectable by a ground-based antenna.

 Posted by at 2:55 pm
Sep 172013
 

It has been known for some time: In the past decade, perhaps decade and a half, there was no significant global warming.

There are many explanations proposed for this slowdown/pause, and the actual cause is likely a combination of these: ocean surface cooling, natural climate oscillations, an unusual solar minimum, water vapor, aerosols, you name it.

Here is one problem with these explanations: These are the same ideas that were proposed, as alternatives to anthropogenic CO2, as causes behind the observed warming, by climate change “skeptics”, only to be summarily dismissed by many in the climate change community as denialist crackpottery.

Sadly, this may very well mean that climate skeptics will claim victory, and those inclined to listen to them will conclude that all this global warming hogwash was just some scam dreamed up by Al Gore and his cronies. Meanwhile, we tend to forget about other things that elevated atmospheric CO2 levels do, such as ocean acidification; not to mention other, equally threatening global environmental concerns, for instance species extinction occurring on a scale not seen since the day of the dinosaurs.

 Posted by at 7:43 pm
Sep 062013
 

Last December, I wrote a blog entry in which I criticized one aspect of the LHC’s analysis of the scalar particle discovered earlier this year, which is believed to be the long sought-after Higgs boson.

The Higgs boson is a scalar. It is conceivable that the particle observed at the LHC is not the Higgs particle but an “impostor”, some composite of known (and perhaps unknown) particles that behaves like a scalar. Or, I should say, almost like a scalar, as the ground state of such composites would likely behave like a pseudoscalar. The difference is that whereas a scalar-valued field remains unchanged under a reflection, a pseudoscalar field changes sign.

This has specific consequences when the particle decays, apparent in the angles of the decay products’ trajectories.

Several such angles are measured, but the analysis used at the ATLAS detector of the LHC employs a method borrowed from machine learning research, called a Boosted Decision Tree algorithm, that synthesizes a single parameter that has maximum sensitivity to the parity of the observed particle. (The CMS detector’s analysis uses a similar approach.)

The result can be plotted against scalar vs. pseudoscalar model predictions. This plot, shown below, does not appear very convincing. The data points (which represent binned numbers of events) are all over the place with large errors. Out of a total of only 43 events (give or take), more than 25% are the expected background, only 30+ events represent an actual signal. And the scalar vs. pseudoscalar predictions are very similar.

This is why, when I saw that the analysis concluded that the scalar hypothesis is supported with a probability of over 97%, I felt rather skeptical. And I thought I knew the reason: I thought that the experimental error, i.e., the error bars in the plot above, was not properly accounted for in the analysis.

Indeed, if I calculate the normalized chi-square per degree of freedom, I get \(\chi^2_{J^P=0^+} = 0.247\) and \(\chi^2_{J^P=0^-} = 0.426\), respectively, for the two hypotheses. The difference is not very big.

Alas, my skepticism was misplaced. The folks at the LHC didn’t bother with chi-squares, instead they performed a likelihood analysis. The question they were asking was this: given the set of observations available, what are the likelihoods of the scalar and the pseudoscalar scenarios?

At the LHC, they used likelihood functions and distributions derived from the actual theory. However, I can do a poor man’s version myself by simply using the Gaussian normal distribution (or a nonsymmetric version of the same). Given a data point \(D_i\), a model value \(M_I\), and a standard deviation (error) \(\sigma_i\), the probability that the data point is at least as far from \(M_i\) as \(D_i\) is given by

\begin{align}
{\cal P}_i=2\left[1-\Psi\left(\frac{|D_i-M_i|}{\sigma_i}\right)\right],
\end{align}

where \(\Psi(x)\) is the cumulative normal distribution.

Now \({\cal P}_i\) also happens to be the likelihood of the model value \(M_i\) given the data point \(D_i\) and standard distribution \(\sigma_i\). If we assume that the data points and their errors are statistically indepdendent, the likelihood that all the data points happen to fall where they fell is given by

\begin{align}
{\cal L}=\prod\limits_{i=1}^N{\cal P}_i.
\end{align}

Taking the data from the ATLAS figure above, the value \(q\) of the commonly used log-likelihood ratio is

\begin{align}
q=\ln\frac{{\cal L}(J^P=0^+)}{{\cal L}(J^P=0^-)}=2.89.
\end{align}

(The LHC folks calculated 2.2, which is “close enough” for me given that I am using a naive Gaussian distribution.)

Furthermore, if I choose to believe that the only two viable hypothesis for the spin-parity of the observed particle are the scalar and pseudoscalar scenarios (e.g., if other experiments already convinced me that alternatives, such as intepreting the result as a spin-2 particle, can be completely excluded) I can normalize these two likelihoods and interpret them as probabilities. The probability of the scalar scenario is then \(e^{2.89}\simeq 18\) times larger than the probability of the pseudoscalar scenario. So if these probabilities add up to 100%, that means that the scalar scenario is favored with a probability of nearly 95%. Not exactly “slam dunk” but pretty darn convincing.

As to the validity of the method, there is, in fact, a theorem called the Neyman-Pearson lemma that states that the likelihood-ratio test is the most powerful test for this type of comparison of hypotheses.

But what about my earlier objection that the observational error was not properly accounted for? Well… it appears that it was, after all. In my “poor man’s” version of the analysis, the observational error was used to select the appropriate form of the normal distribution, through \(\sigma_i\). In the LHC’s analysis, I believe, the observational error found its was into the Monte-Carlo simulation that was used to develop a physically more accurate probability distribution function that was used for the same purpose.

Even clever people make mistakes. Even large groups of very clever people sometimes succumb to groupthink. But when you bet against clever people, you are likely to lose. I thought I spotted an error in the analysis performed at the LHC, but all I really found were gaps in my own understanding. Oh well… live and learn.

 Posted by at 4:12 pm
Sep 032013
 

One of the giants of the golden era of science-fiction, indeed a co-author of one of the most influential science-fiction novels of all time, The Space Merchants, passed away yesterday, just a few weeks shy of his 94th birthday.

I think it would be a fitting tribute if a future space probe took his ashes to Venus and scattered it in the planet’s atmosphere.

 Posted by at 11:12 am
Jul 272013
 

I was watching RDI’s coverage of the memorial ceremony that was taking place last hour in Lac-Mégantic, the location of the horrific derailment a few weeks ago that claimed so many lives.

I was impressed by the size and beauty of Sainte-Agnés church where the mass was taking place, so I went to Google to find out more.

It was, of course, unsurprisingly difficult to find background material, as search results were dominated by recent articles about the disaster. But, after wading through some directory entries and such, I came across a true gem: the story of the “Electrical Priest”, Father Joseph-Eugene Choquette.

When he was not attending to his priestly duties, Father Choquette spent a fair bit of his time as an amateur scientist. And what an amateur he was!

Bringing a player piano to his church (and drawing the ire of his parishioners when they found out that it was not their vicar who was in secret a talented musician) was just one of his many pranks (perhaps an unintended one in this case). Apparently, he also liked to play with electricity, to the extent that visitors to his house were often shocked by a jolt of current when they touched a doorknob or sat down in a booby-trapped chair.

But Father Choquette was interested in more than mere pranks. He also experimented with telephony and electric lighting. Having installed a personal lighting system (powered by a dynamo hooked up to a windmill) that proved to be a success, he proceeded with a more ambitious plan: a generating plant to light the whole town. He remained directly involved with this project until his death; parishioners often found their vicar strapped to a pole 25 feet in the air, working on a faulty transformer.

When Father Choquette died, he left much of his equipment and collections to the Sherbrook and Saint-Hyacinthe Seminaries and to the Convent and College of Megantic. That was nearly a century ago. I wonder if any of his belongings still survive somewhere.

 Posted by at 1:10 pm
Jul 202013
 

I spent a part of yesterday afternoon speed-reading Konstantin Kakaes’s new e-book, The Pioneer Detectives. It’s a short book (still well worth the $2.99 Kindle price) but it reads very well and presents a fair picture of our efforts researching the origin of the anomalous acceleration of the Pioneer 10 and 11 spacecraft.

Yes, I was one of those “detectives”. (In fact, I still consider myself one, as I don’t believe our job is quite done yet; we still owe the community a detailed account of our research and an update of our Pioneer Anomaly review before we can move on with a clean conscience.) So I have an insider’s view of this very intriguing story.

I had a chance to talk with Kakaes at length when he visited me here in Ottawa last year. Over the years, I learned to be apprehensive when talking to journalists; often, the words they put in your mouth bear little resemblance to what you actually said to them when interviewed. I was relieved that this was not the case now: at no time did I feel compelled to cringe while reading the book.

So I really enjoyed Kakaes’s telling of our story. Indeed, I think I learned a thing or two about presenting a complex subject to a non-specialist audience. Kakaes, an accomplished science journalist, manages to do so without dumbing it down with excessive oversimplifications.

One person whose views may not be as favorable is the original discoverer of the Pioneer anomaly, John Anderson. I am told that Anderson is not fond of our results. Kakaes believes that this is because Anderson is “blinded by his desire to believe in something new, in something unexplained. He wants so badly not to know.” Yes, scientists are people, too, and the prospect that a discovery you made, once thought profound, may just be an engineering fluke is not an easy one to swallow. Kakaes does what a responsible journalist must do: he tries to paint an objective picture, which sometimes includes unflattering bits. Yet I think that John Anderson has more scientific integrity than Kakaes gives him credit for.

And to be perfectly honest, I am also disappointed with our own results. When I first read about the Pioneer anomaly (as an outsider, long before my involvement) it seemed to fit perfectly into the big scheme: namely that perhaps the same physics that was responsible for significant deviations from Einstein’s and Newton’s predictions on cosmological and galactic scales might also be responsible for a small but measurable deviation here in the solar system. This was a fantastic prospect!

Sadly, it was not to be. What once seemed like a revolutionary, paradigm-shifting result has been reduced to a small footnote in the history of gravitational physics. Yet I think that our story is nonetheless intriguing. Kakaes seems to think so, too, judging by his book. A book that I am happy to recommend.

 Posted by at 6:55 pm
Jun 092013
 

The other night, Curiosity was working late.

You walk around on the surface of a planet, and it is pitch dark. Suddenly, you spot a light on the horizon. It’s steady; it’s artificial. You conclude that it’s a sign of civilization.

And indeed it is. What you see is an artificial light… but it belongs not to a living creature but to a robotic explorer. One that was created by a civilization a couple of hundred million kilometers away. A civilization that only invented electric lighting just over two centuries earlier.

light-on-mars

I find it eerily beautiful to see an artificial light bathing the rocky surface of an alien planet.

 Posted by at 10:26 pm
May 242013
 

Physics blog sites are abuzz about Eric Weinstein and his Amazing New Theory of Everything. For a moment, I actually confused him with Eric Weisstein, well known in physics and math circles as the founder of Mathworld, which, in the pre-Wikipedia days, was the Internet’s pre-eminent mathematics encyclopedia (only to be hijacked for a while by an unscrupulous CRC press). No, Weinstein is someone else: he is a mathematical physicist turned economist. In any case, he is no dummy, nor does he appear to be a crackpot. He is outside of academia, but, well, so am I, so who am I to complain?

So Weinstein gets invited to Oxford to give a public lecture, and he talks, for the first time, about ideas he has been working on for the past twenty years, about unifying physics.

This is greeted by a headline in The Guardian that reads, “Roll over Einstein: meet Weinstein“. Others follow suit, and soon physics news and blog sites far and wide discuss… what, exactly? Well, no-one really knows.

That is because Weinstein has not published anything yet. Not even a non-peer reviewed manuscript on arxiv.org. This is pointed out in one of the few sensibly skeptical blog posts, written by Jennifer Ouellette on Scientific American’s blog site. Ouellette actually quotes a tweet by Sean Carroll: “Pretty sure Einstein actually wrote research papers, not just gave interviews to newspapers.”

Ouellette goes on to quote Oxford cosmologist Andrew Pontzen, who observes that these “shenanigans” have “short-circuited science’s basic checks and balances”. I couldn’t agree more. This is true even if Weinstein turns out to be right in the end.

Which is conceivable, since Weinstein is no crackpot. But it is much more likely that his theory will join many others, including Garrett “surfer dude” Lisi’s aesthetically beautiful E8 theory, that just don’t have much to do with observable reality.

 Posted by at 10:24 pm
Apr 252013
 

Twenty seven years ago tonight, an ill-prepared overnight crew at reactor #4 at the Chernobyl nuclear power station in the Ukraine began an unauthorized experiment, originally scheduled to run during the day, and designed to test how much power the reactor was able to supply while it was shutting down, keeping emergency systems powered while waiting for backup generators to kick in. Trouble is, this particular reactor type was known to have instabilities at low power even at the best of times. And these were not the best of times: the reactor was operated by an inexperienced crew and was suffering from “poisoning” by neutron-absorbing xenon gas due to prolonged low-power operations earlier and during the preparation for the test.

The rest, of course, is history: reactor #4 blew up in what remains the worst nuclear accident in history. A large area around the Chernobyl plant remains contaminated. The city of Pripyat remains a ghost town. And a great many people were exposed to radiation.

The number of people killed by the Chernobyl disaster remains a matter of dispute. Most studies I’ve read about estimate several thousands deaths that can be attributed to the accident and the resulting increased risk of cancer. But a recent paper by Kharecha and Hansen (to be published in Environ. Sci. Technol.) cites a surprisingly low figure of only 43 deaths directly attributable to the accident.

This paper, however, is notable for another reason: it argues that the number of lives saved by nuclear power vastly exceeds the number of people killed. They assert that nuclear power already prevented about 1.8 million pollution-related deaths, and that many million additional deaths can be prevented in the future.

I am sure this paper will be challenged but I find it refreshing. For what it’s worth, I’d much rather have a nuclear power plant in my own backyard than a coal-fired power station. Of course the more powerful our machines are, the bigger noise they make when they go kaboom; but this did not prevent us from using airplanes or automobiles either.

 Posted by at 9:34 pm
Apr 202013
 

It’s official (well, sort of): global warming slowed down significantly in the last decade and a half.

No, this does not mean that the climate skeptics were right all along. Far from it: their attacks on science, their ad hominem attacks on scientists, their conspiracy theories are all nonsense.

What it does mean, though, is that the climate alarmists were not exactly right either. Overstating the case did not help. Far from creating public support, it may have in fact fueled climate skepticism.

The basic science is not wrong. Take a gas like CO2 that is transparent to visible light but absorbs IR a little more efficiently. Pump it into the atmosphere. Visible sunlight still reaches the surface, but less heat escapes radiatively to space at night. So, the surface gets warmer. Simple. This much was known back in the 19th century, to people like Fourier in 1827, Tyndall in 1872, and last but not least, Arrhenius from Sweden who, in 1896, actually calculated the amount by which the Earth would warm up, or cool, if the amount of CO2 were to change in the atmosphere.

But the devil is in the details. The Earth’s atmosphere is not just a column of static, transparent air with various amounts of CO2. It is a turbulent thing, with many feedback mechanisms, some positive, some negative. The oceans play a big role. Foliage plays a big role. Changes in industrial practices, fewer particulates in the air, play a big role. And so on.

And we also know that the Earth’s climate is not exactly a fragile little thing. After all, it has been relatively stable over geological timescales, allowing life to flourish and evolve. So I always thought that it is rather preposterous to assume that a few hundred years of industrial pollution can do what geological upheavals, global catastrophes, and so on could not: tip the balance and cause a runaway effect.

So we are left with the basic questions. How much will the climate change in the foreseeable future? What are its effects on humanity? And what can we do about all this?

The answer, I fear, remains as elusive as ever. And ridiculous schemes like “carbon trading” don’t help either.

 Posted by at 10:40 pm
Apr 162013
 

There is another ambitious Mars project in the works: unlike Inspiration Mars, the Mars One project aims to send colonists to Mars, people determined to live out the rest of their lives on the Red Planet, with no return ticket.

Mars_One

I wrote about how I would be willing to risk a very dangerous, very uncomfortable 501-day flight to Mars and back. But staying there for good? Now that’s another matter. Leaving the Earth in the company of a dozen or so other people, knowing that from now on, those will be the only people you will ever see face to face? That you will never see a blue sky again, hear a bird sing, or swim in the sea?

Fortunately, this is not a choice I’ll ever have to make. Unlike Inspiration Mars, the Mars One project is not (to the best of my knowledge) looking for middle-aged couples as participants.

 Posted by at 3:29 pm
Apr 162013
 

In all the excitement (okay, I wasn’t that excited. But, I was busy) I almost forgot to celebrate an anniversary: it was 40 years ago on April 5 that Pioneer 11 was launched at Cape Canaveral.

In a recent Letter to the Editor published in the newsletter of the American Physical Society, a correspondent suggested that Pioneer 11 may still reveal some anomalous behavior. I do not believe this to be the case. While it is true that our investigation of Pioneer 11 was not as thorough as our investigation of Pioneer 10 (due, in part, to the fact that we have less Doppler data from Pioneer 11) there are no statistically significant inconsistencies.

This Letter also reveals two misconceptions about the anomaly. One is that if the anomaly is Earth directed, which would presumably be inconsistent with a thermal cause. This is not so: quite the contrary, since the spin axis and the Earth direction mostly coincide, an Earth directed anomaly is exactly what one would expect to see in case of a thermal cause. Second, I don’t think it is even relevant to say that “a new physics cause may still be possible”. Of course new physics is always possible. But before one can speculate about new physics, “old physics” must be excluded, i.e., there must be an incontrovertible demonstration that conventional physics cannot account for the observed phenomena. This is not the case for the Pioneer anomaly: conventional physics comfortably accounts for the anomalous acceleration. Sure, there are small discrepancies that are within the margin of error, but you don’t fish for new physics within the margine of error. That’s not the way science is supposed to work.

 Posted by at 9:55 am
Apr 102013
 

A few moments ago, my wife looked up through our skylight and lo and behold, saw a moving star.

Not just any moving star; it turned out to be the International Space Station, in all its still sunlit glory over the late evening Ottawa sky.

I once managed to capture the ISS through my cellphone; the picture turned out to be surprisingly good, even showing (I think) the somewhat rectangular shape of the station.

Anyhow, I hope Chris Hadfield is having a great time up there.

 Posted by at 9:45 pm