Our paper on the temporal behavior of the anomalous acceleration of Pioneer 10 and 11 is now published online by Physical Review Letters, and it is an Editor’s Suggestion, featured in Physical Review Focus.
Aug 192011
Aug 122011
I am reading a very interesting paper by Mishra and Singh. In it, they claim that simply accounting for the gravitational quadrupole moment in a matter-filled universe would naturally produce the same gravitational equations of motion that we have been investigating with John Moffat these past few years. If true, this work would imply that that our Scalar-Tensor-Vector Gravity (STVG) is in fact an effective theory (which is not necessarily surprising). Its vector and scalar degrees of freedom may arise as a result of an averaging process. The fact that they not only recover the STVG acceleration law but the correct numerical value of at least one of the STVG constants, too, suggests that this may be more than a mere coincidence. Needless to say, I am intrigued.
Aug 012011
First the first time in seven years (!), my main Internet connection is down, and will likely stay down until at least Tuesday. This being a long weekend, no telco technician is available until then, and they determined that the fault is likely a partial short in the physical circuit. Bloody hell.
Now I am scrambling to reroute everything to a backup server, provided courtesy of a good friend of mine. I asked him to only move around on tiptoes until Tuesday, and I am begging Murphy not to strike again until then…
Jul 222011
Human memory is far from perfect.
During the winter of 1988-1989, I was renting a small office on Ottawa’s Bank Street with my business partner John. We spent many a late night working on a difficult project, and it was one cold winter. I distinctly remember one night when the temperature dipped to −36 degrees Centigrade, and I not only had a hard time starting my car (only to rush back to the building to warm up and then run out to the car again after a few minutes in the hope that it would have warmed up a little by then) but its engine never reached its normal operating temperature during the 10 km drive home.
Except that it never happened. The -36°C, that is. The coldest historical temperature I can find for that winter is −27.2°C, which occurred in early March 1989; earlier, in January, it went down to −27.0°C one night.
I also distinctly remember that the first winter my wife spent here in Ottawa, she was renting a stall on the Byward Market and that on Christmas Eve day, the temperature never climbed above −24°C.
Again, never happened. On December 24, 1992, the high temperature was +2.7°C. Perhaps a year later, then? Yes, that was a cold Christmas Eve day, but not near that cold; the high temperature was -10.0°C.
Then there is that very cold winter in Budapest that I recall. It was brutal; my old Lada’s engine half froze. Eventually I managed to get it running without overheating, and then I spent half the night looking for a gas station that was selling antifreeze. Eventually I found one, way outside of Budapest. I do recall hearing on the radio that the temperature was -29°C. It wasn’t… according to the historical weather records that I can locate, the coldest night was on February 12, 1985, with a temperature of −24°C. Brutally cold by Budapest standards to be sure, but still 5 degrees warmer than what I remember.
At least I do know for a fact that today, the temperature reached +36°C. I think I owe an extra prayer of thanks to the gods of air conditioning.
Jul 192011
I found out that I am less squeamish than I thought.
I went out for a walk this morning, and in the middle of a sidewalk, I suddenly spotted a mouse. First I thought it was a small furry mouse toy, as it looked like a perfect little mouse, completely motionless. But then I realized it was the real thing, probably dead… but no, wait, it was still kicking. When I touched it with the toe of my shoe, it squeaked loudly and tried to crawl away… but even though I was trying to steer it towards the grass with my shoe, it didn’t get very far. I think it was badly injured, probably a broken leg or something. Eventually, fears of hantavirus and whatnot notwithstanding, I just grabbed it by the tail (loud squeaks followed) and threw it in the grass.
I mean, what was I supposed to do, step on the poor thing? Yes, I know, too much empathy is bad for your health, but apart from their size, mice are not that different from other mammals… they have hearts, lungs, a sizable brain, and the ability to feel fear and pain. In all likelihood, this poor critter has since been found by a cat, but at least it’s not expiring in the middle of a sidewalk half crushed to death when someone steps on it.
Yes, I avoided touching my face afterwards and washed my hands as soon as I got back home.
Jul 142011
Our paper on the analysis of extended Pioneer 10 and 11 Doppler data was just accepted by Physical Review Letters.
In it, we report that a data set roughly twice in size the data set that was analyzed previously continues to support the notion that a small anomalous acceleration is affecting both spacecraft. However, there is no reason to believe that the acceleration is in the direction of the Sun or that it is constant; on the contrary, the data seem to favor (albeit weakly) an Earth-directed, temporally decaying acceleration model.
Heat, emitted anisotropically, remains the prime suspect. The observed decrease in the acceleration appears more rapid than the rate of decay of the radioactive fuel on board. This is explained once we consider that much of the thermal acceleration would be due to electrically produced heat, and the amount of electricity available on board decreases much more rapidly. (The reason is that as the plutonium fuel cools, the thermocouples used to generate electricity become less efficient; the thermocouples also age.)
We also looked at some early data, taken when Pioneer 11 was cruising between Jupiter and Saturn. The possibility that the anomalous acceleration only began after Pioneer 10 and 11 passed the orbit of Saturn was much discussed in the literature. While we cannot exclude such an onset, its presence cannot be confirmed either (the early data is just too short in duration for a definitive conclusion). In any case, the shape of the onset curve very strongly suggests that it is, in fact, a modeling artifact: it is precisely what one would see if the Pioneer spacecraft’s solar pressure model was miscalibrated, which is a very likely possibility.
In the past few years, we also constructed a detailed thermal model of the Pioneer spacecraft, using recovered documentation and telemetry. We are busy preparing another report in which the results of this effort will be discussed.
Jul 072011
This morning my main server greeted me with an unexpected and unpleasant surprise: it no longer recognized its video card. This problem has happened before (removing and reinserting the video card fixed it) but this time around, I decided that rather than investing the time into fixing the old server, I should finally complete the setup of my new server, which has been in a half-finished state for months.
Well, to make a long story short, I am now writing this using the brand spanking new server, and just about everything works… but it was a pretty much non-stop 15 hours and I am tired like a horse. A few more hours to go tomorrow, fixing things like temperature sensor drivers or the UPS software.
Groan.
Jul 012011
Canada is 144 years old today. That is 12², or a dozen dozen. I am four dozen years old, and spent the last two dozen of these years here in Canada. Wonder what else is divisible by 12 this year.
Jun 042011
I am an atheist. To the best of my knowledge, there is no such thing as heaven, not even kitty heaven. That means that when a cat dies, it is truly dead.
That does not stop me from imagining, though, that in a sense, our two cats Marzipan and Tarka are still with us, perhaps watching our house while we sleep, as these cats do in a wonderful New Yorker cartoon titled Vigil:
May 232011
And then, there were only four. Cats, that is… our oldest cat, Tarka, our last 20th century cat and the last cat that actually knew our first cat, is no longer with us.
We adopted Tarka over 11 years ago, during the winter of 1999-2000. Shortly thereafter, she settled in a cardboard box that was already a few sizes too small for her. We still have that box.
Good bye.
May 072011
Tarka is our oldest cat and she is not doing very well. Her kidneys are failing.
The day before yesterday, her appetite suddenly vanished, and she became lethargic, urinating outside the litter box. I became rather worried, so yesterday I took her to the vet, who determined that in addition to the ailing kidneys, she may also be suffering from hyperthyroidism. They took a blood sample (we’re still waiting for the results), gave her some fluids, and some new medication, and sent her home.
What can you do? In an ailing organism, as one subsystem after another begins to fail, they struggle to keep up and compensate for the failures of one another. It’s like the ever narrowing flight envelope of a high altitude airplane; if you’re a little faster, the airplane breaks apart, if you’re a little slower, it falls out of the sky, and the difference between the two velocities becomes more marginal the higher the airplane flies. (This, combined with a faulty airspeed indicator, may have been one of the causes of the Air France tragedy two years ago.) So how do we keep Tarka flying true for at least a while longer?
I don’t know… yesterday, after I got her back home, she was doing better, eating more than the day before. But today, she hasn’t eaten anything yet and she’s even more lethargic. Is it time to get seriously worried yet? Another visit to the vet may accomplish little beyond exposing her to yet more stress.
Mar 172011
Today, a Home Hardware store just across the Rideau River here, one we visited frequently, went up in flames, along with several other businesses, as the whole building was demolished by firefighters combating a toxic column of smoke. I don’t yet know if my favorite barber shop, Lester’s, which is right next door, survived or not.
Feb 012011
Two weeks ago, I took a stray cat to the Humane Society. I thought it was the right thing to do; we already have five of them, no friend of ours wanted a cat, and this stray was obviously not going to do well outdoors (when we first saw him, he was eating some scraps off the pavement in the middle of a street frequented by city buses.) He was also young, healthy, and friendly, so we had every hope that he would be adopted.
Our hopes were in vain. Today, I found out that he was put down after contracting a viral respiratory infection and some secondary bacterial infection that did not respond to antibiotics.
All we have now is this last picture, courtesy of the Humane Society:
Well, that’s the end of one little life. Wasn’t worth much, I guess.
Not sure what to do next time. Would he have had a better chance outside in -30 Centigrade weather?
Damn.
Jan 252011
I just ran this on my main server:
$ uptime 08:13:32 up 365 days, 19:56, 4 users, load average: 0.07, 0.05, 0.06
Yes, this means I last rebooted this server one year and 20 hours ago. (What was I doing, rebooting at 4 in the morning?)
Mind you, it won’t run uninterrupted much longer. An updated server is waiting to take its place, so that I can then take this guy down, thoroughly clean it (removing one year’s worth of accumulated dust and cat hair) and upgrade it as well.
Jan 152011
This morning, I took this little guy to the Humane Society:
This young, unneutered tomcat showed up at our doorstep during the holidays, obviously homeless and hungry, but otherwise in good shape and friendly. We took care of him but the weather is getting colder, and spending much of his day in our tiny entry hall isn’t exactly a solution. We already have five cats, so adopting him was not a good idea.
On the way to the Humane Society, as the sun shone into the car, I noticed that he had blue-ish eyes. He was obviously part Siamese, but the blue eyes were news to me.
I hope he finds a good owner soon and lives a long and happy life.
Dec 242010
My Linux systems are all configured with an ages old program, fortune, giving me a “fortune cookie”, a random greeting or quotation from a database with thousands of entries, every time I log on.
This morning, I logged on to one of my Linux machines and I saw this quote from the immortal Sam Clemens, aka. Mark Twain:
“The difference between a Miracle and a Fact is exactly the difference between a mermaid and a seal.”
If I didn’t know any better, I’d be tempted to think that the computer has a twisted sense of atheist humor and chose this greeting after looking at the calendar. Not that Mr. Clemens was wrong!
Anyhow, although I am an atheist, I hope I am not twisted, so I just wish a Merry Christmas to all my family and friends, and indeed, all good people.
Dec 162010
It’s official: the work we are doing about the Pioneer Anomaly qualifies as popular science according to Popular Science, as they just published a featured article about it.
I admit that it was with a strong sense of apprehension that I began reading the piece. What you say to a journalist and what appears in print are often not very well correlated, as politicians know all too well. My apprehension was not completely unjustified, as the article contains some (minor) technical errors, misquotes us slightly in places, and what is perhaps most troubling, some of the work that it attributes to us was done by others (e.g., thermal engineers at JPL). These flaws notwithstanding (and this article fares better than most that appeared in recent years, I think), it is nice to have one’s efforts recognized.
Dec 132010
In the pre-Internet days, when I traveled to a city that I never visited before, the first thing I did was to buy a copy of the local newspaper, and then read the local pages and some of the classifieds.
Now, thanks to the Internet, I can time travel the same way, without leaving my chair. For instance, I can browse the pages of the Ottawa citizen from 1973, the year my Mom and I visited this fine city. Not sure what is weirder… how much has changed or how much remained the same.
Nov 212010
This sunset above an eerie landscape of orange-lit clouds looked much nicer to the naked eye than it looks in a picture:
Yes, it means that I am back home. As a matter of fact, I arrived back home some 2.5 hours early. My flight from Mexico City landed 15 minutes early in Toronto, and after dashing through the airport like crazy, I managed to make it to an earlier Ottawa flight… which had ONE (!) seat left. Talk about luck.
It was an interesting conference. Useful discussions, good people to meet. I had a chance to talk about MOG cosmology to a not altogether unfriendly audience.
Still, it’s good to be home. Sleep in my own bed and all that.
Nov 182010
This is John Moffat, talking about blogs, dark matter, and the Bullet Cluster:
It’s going to be my turn Friday. Of course I won’t be able to take a picture of me.