This was the view from my window late last night, before I went to sleep:
Now this is a perfectly normal way for our street to appear, say, in January… but April 7?
Really, people, if the rest of the world doesn’t care, I am all for global warming.
Sometime last year, I foolishly volunteered to manage new releases of the Maxima computer algebra system (CAS).
For the past several weeks, I’ve been promising to do my first release, but I kept putting it off as I had other, more pressing work obligations.
Well, not anymore… today, I finally found the time, after brushing up on the Git version management system, and managed to put together a release, 5.38.0.
Maxima is beautiful and incredibly powerful. I have been working on its tensor algebra packages for the past 15 years or so. As far as I know, Maxima is the only general purpose CAS that can derive the field equations of a Lagrangian field theory; for instance, it can derive Einstein’s field equations from the Einstein-Hilbert Lagrangian.
I use Maxima a lot for tensor algebra, though I admit that when it comes to integration, differential equations or plotting, I prefer Maple. Maple’s ODE/PDE solvers are unbeatable. But when it comes to tensor algebra, or just as a generic on-screen symbolic calculator, Maxima wins hands down. I prefer to use its command-line version: Nothing fancy, just ASCII art, but very snappy, very responsive, and does exactly what I want it to do.
So then, Maxima 5.38.0: Say hi to the world. World, this is the latest version of the oldest (nearly half a century old) continuously maintained CAS in existence.
Not sure how it happened, but it appears that I was a successful political animal today. Kevin McCarthy, House leader in the U.S. Congress, held a question-and-answer session on Quora today, and my question (about Obama’s SCOTUS nomination) turned out to be the top question, which he answered first. Not sure if that is a good thing… after all, I remember all too well the saying, “it’s better to be unknown to the gods than to be loved by them.” Predictably, the answer was a party line answer with very little information content, but still.
Tempting fate a little further, I also created an updated version of an infographic that compares the truthfulness of presidential candidates. Despite her reputation as untrustworthy, and much to my surprise I admit, Hillary Clinton is still pretty much on top (same number of true/mostly true answers as Sanders and Kasich, but fewer untruths).
Not that this will stop Trump’s supporters from voting for him. They’ll just declare Politifact biased and full of lies or whatever.
Yesterday, I went to see my barber. When I found the shop open, I was delighted that he kept his promise: he planned to retire at the end of last year, but on my last visit, he told me that he’d be keeping the shop open for a while longer. (Yes, it’s been that long since my last haircut. I don’t like haircuts, but when even my wife notices that I am beginning to look like Albert Einstein, I remind myself that you first have to match Einstein’s output as a physicist before you’re allowed to look like him.)
When I entered the shop, I noticed that it was under renovation. But the sign said that it was open! In fact, it was a brand new electronic sign that advertised the business hours. I didn’t see a soul in sight so I hollered, “hello?” and a young, brown-skinned man soon emerged. He assured me that the shop was indeed open for business, so I made the requisite leap in logic and realized that Michel, the old barber, must have retired after all. I asked the young man if he was going to be my new barber.
Soon, I learned a little bit about Paulos the barber. He came to Canada from Ethiopia about five years ago with his brother. Since then, they managed to sponsor several family members. Paulos is a lean, tall 41-year old man, though he looks much younger. He told me that he found the shop advertised on Kijiji and decided to go for it. He told me of his plans to hire 2-3 additional barbers, and create a much more welcoming shop with Wi-Fi and a coffee machine. I took a closer look at his hours: He is keeping the shop open, for now all by himself, from 9 AM until 8 PM every weekday, and until 6 PM on Saturdays.
Meanwhile, Paulos finished my haircut. When I asked him how much I owe, he told me that it’s whatever I used to pay Michel. So I paid the same amount, with tip, that I used to pay.
As I left the barber shop, I was shaking my head. Damn immigrants, I thought. They have the audacity to come to this country in search of a better life. And the cheek! Never mind making a living, working extra long hours, they actually plan to create jobs! How dare they.
And the cultural rift. It is hard to find a pair of countries more culturally different than Ethiopia and Canada. Yet he has the chutzpah to do this… finding his place in Canadian society, taking over a business from a retiring French Canadian gentleman and daring to be successful.
What a horrible thing that these immigrants are doing. What hubris… instead of being on welfare and being a burden on society, they dare to make this country better, enrich it with their hard work, contribute to its colorful multiculturalism. It is absolutely intolerable. Just what is this place coming to?
Our long-serving Member of Parliament, Mauril Bélanger, was the recipient of an unprecedented honor today: He was named honorary Speaker of the House.
Unfortunately, we could not hear Mr. Bélanger speak. That is because he is suffering from ALS, or Lou Gehrig’s disease (its most famous sufferer alive is the physicist Stephen Hawking), which is rapidly progressing; since his initial diagnosis last fall, he lost the ability to speak, so it was his iPad that was speaking for him.
The illness also ended his dream of becoming Speaker of the House, which explains the honor that has been bestowed on him today.
I have a lot of respect for Mr. Bélanger. Over the years, I wrote to him a few times with my concerns, and on more than one occasion I received a personal response, either in the form of a latter or, in one case, in the form of a telephone call. In short, Mr. Bélanger appeared to take the idea of representing his constituents very seriously.
He may have lost the ability to speak but he has not yet lost all his mobility. Although he needed some help, he was able to walk into the Chamber on his own two feet.
It was a moving moment, and I am glad I caught it on the CBC. Thank you, Mr. Bélanger.
The other day, I saw this media photo of a SpaceX rocket that was readied for launch:
The photographer’s choice to include the No Photography sign in this picture reminded me of a No Photography sign I saw a few years ago in Budapest, at a construction site in the vicinity of the US embassy:
These signs are ridiculous. You don’t see them often in democracies; they were very frequently encountered in the former Soviet Bloc. Which once made me wonder… all a Western spy had to do was to drive around the country and mark the location of No Photography signs in order to get a fairly accurate map of all the communist regime’s sensitive installations.
In the era of the ubiquitous smartphone with HD camera, not to mention more advanced gadgets like Google’s Glass or even toy drones with HD video, these signs are pitifully pointless.
Here is a spectacular photograph of the Moon made last night by my good friend David Ada-Winter in light-polluted New Jersey:
David explains: “I took this picture of the Moon using the so-called Sunny 16 rule, the essence of which is the following: On a clear day, with an aperture of 16, the exposition time must be the reciprocal of the ISO value. In the case of this picture, the ISO was 200, so the exposition time was 1/200 with an aperture of 16. In front of my telescopic lens, I also used a doubler that extended the focal length to 800 mm. The picture itself was made with the Canon Rebel t2i camera, which has a crop factor of 1.6, allowing the Moon to appear even larger in the image.”
Apparently, David’s wife disapproves of his pricey hobby. I’m tempted to remind her that other men of David’s age often acquire even pricier hobbies, which usually involve brightly colored sports cars and lightly clad ladies…
This is what greeted me earlier this morning when I looked at my outdoor thermometer:
Brrrr. And tomorrow it’s supposed to get even colder. Where is that global warming that we were promised?
I’ve become a calendar boy.
Or to be more precise, an illustration in a paper that my friend and colleague, Eniko Madarassy and I published together early last year in Physical Review D found its way to the 2016 calendar of the American Physical Society.
Now if only it came with perks, such as getting a discount on my APS membership or something… but no, in fact they didn’t even bother to tell us that this was going to happen, I only found out today when I opened my mailbox and found the calendar inside. Oh well… It was still a nice surprise, so I am not complaining.
It is nice to have a paper accepted on the penultimate day of the year by Physical Review D.
Our paper in question, General relativistic observables for the ACES experiment, is about the Atomic Clock Ensemble in Space (ACES) experiment that will be installed on board the International Space Station (ISS) next year. This experiment places highly accurate atomic clocks in the microgravity environment of the ISS.
How accurate these clocks can be depends, in part, on knowledge of the general relativistic environment in which these clocks will live. This will be determined by the trajectory of the ISS as it travels through the complex gravitational field of the Earth, while being also subject to non-gravitational forces, most notably atmospheric drag and solar radiation pressure.
What complicates the analysis is that the ACES clocks will not be located at the ISS center-of-mass; therefore, as the ISS is quite a large object subject to tidal accelerations, the trajectory of the ACES clocks is non-inertial.
To analyze the problem, we looked at coordinate transformation rules between the various coordinate systems involved: geocentric and terrestrial coordinates, coordinates centered on the ISS center-of-mass, and coordinates centered on ACES.
One of our main conclusions is that in order for the clock to be fully utilized, the orbit of the ISS must be known at an accuracy of 2 meters or less. This requirement arises if we assume that the orbits are known a priori, and that the clock data are used for science investigations only. If instead, the clock data are used to refine the station orbit, the accuracy requirement is less stringent, but the value of the clock data for scientific analysis is also potentially compromised.
It was an enjoyable paper to work on, and it is nice to end the year on a high note. As we received the acceptance notice earlier today, we were able to put the accepted version on arXiv just in time for it to appear on the very last day of the year, bearing the date December 31, 2015.
Happy New Year!
It has become a habit of mine. On Christmas Eve Day, I like to offer my best wishes to all my friends, members of my extended family, and indeed to all good people on this Earth with the words of the first three human beings in history who left our planet and entered orbit around another celestial body: The astronauts of Apollo 8, who accomplished their historic mission at the end of one of the most tumultuous years since World War 2, 1968.
And as they emerged from the dark side of the Moon and reestablished radio contact with the Earth, they greeted their fellow humans by quoting from the Book of Genesis. They then finished their broadcast with these unforgettable words: “And from the crew of Apollo 8, we close with good night, good luck, a Merry Christmas and God bless all of you – all of you on the good Earth.“
Here is the Weather Network’s forecast for today that was made a couple of days ago:
No, they weren’t lying. Here is what my thermometer showed just a few minutes ago:
And it’s already less than what it was; the temperature dropped from 16.4 to 16.2 degrees Centigrade in the past half hour.
May not be impressive for a place like Dubai or Mumbai but lest we forget, I live in Ottawa, supposedly the second coldest capital city on Earth.
Needless to say, we are not going to have a white Christmas this year.
The reason for my trip to China was to participate in the 3rd workshop on the TianQin mission.
TianQin is a proposed space-borne gravitational wave detector. It is described in our paper, which was recently accepted for publication in Classical and Quantum Gravity. The name, as typical for China, is poetic: it means a zither or harp in space or perhaps (sounds much nicer in English) a celestial harp. A harp that resonates in response to continuous gravitational waves that come from binary pulsars.
Gravitational waves are notoriously hard to detect because they are extremely weak. To date, we only have indirect confirmation of gravitational waves: closely orbiting binary pulsars are known to exhibit orbital decay that is consistent with the predictions of Einstein’s gravity.
Gravitational radiation is quadrupole radiation. It means basically that it simultaneously squeezes spacetime in one direction and stretches it in a perpendicular direction. This leads to the preferred method of detection: two perpendicular laser beams set to interfere with each other. As a gravitational wave passes through, a phase shift occurs as one beam travels a slightly longer, the other a slightly shorter distance. This phase shift manifests itself as an interference pattern, which can be detected.
But detection is much harder in practice than it sounds. Gravitational waves are not only very weak, they are also typically very low in frequency. Strong gravitational waves (relatively speaking) are produced by binaries such as HM Cancri (aka. RX J0806.3+1527) but even such an extreme binary system has an orbital period of several minutes. The corresponding gravitational wave frequency is measured in millihertz, and the wavelength, in tens or hundreds of millions of kilometers.
There is one exception: inspiraling neutron star or black hole binary systems at the very end of their lives. These could produce detectable gravitational waves with frequencies up to even a kilohertz or so, but these are random, transient events. Nonetheless, there are terrestrial detectors such as LIGO (Laser Interferometer Gravitational-wave Observatory) that are designed to detect such events, and the rumor I heard is that it may have already happened. Or not… let’s wait for the announcement.
But the continuous waves from close binaries require a detector comparable in size to the wavelength of their gravitational radiation. In short, an interferometer in which the laser beams can travel at least a few hundred thousand kilometers, preferably more. Which means that the interferometer must be in space.
This is the idea behind LISA, the Laser Interferometer Space Antenna project. Its current incarnation is eLISA (the “e” stands for “evolved”), a proposed European Space Agency mission, a precursor of which, LISA Pathfinder, was launched just a few days ago. Nonetheless, eLISA’s future remains uncertain.
Enter the Chinese, with TianQin. Whereas eLISA’s configuration of three spacecraft is designed to be in deep space orbiting one of the Earth-Sun Lagrange points with inteferometer arm lengths as long as 1.5 million kilometers, TianQin’s more modest proposal calls for a geocentric configuration, with arm lengths of 150,000 km or so. This means reduced sensitivity, of course, and the geocentric orbit introduces unique challenges. Nonetheless, our colleagues believe that it is fundamentally feasible for TianQin to detect gravitational waves from a known source with sufficient certainty. In other words, the primary mission objective of TianQin is to serve as a gravitational wave detector, confirming the existence of continuous waves emitted by a known binary system, as opposed to being an observatory, usable to find previously unknown sources of gravitational radiation. Detection is always easier: in radio technology, for instance, a lock-in amplifier can be used to detect the presence of a carrier wave even when it is far too weak to carry any useful information.
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| Theoretical sensitivity curve of the proposed TianQin mission. |
The challenges of TianQin are numerous, but here are a few main ones:
Indeed, some of the accuracy requirements of TianQin exceed those of eLISA. This is a tall order for any space organization, and China is no exception. Still, as they say, where there is a will…
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| Unequal-arm Michelson interferometer. |
One thing that complicates matters is that there are legal barriers when it comes to cooperation with China. In the United States there are strong legal restrictions preventing NASA and researchers at NASA from cooperating with Chinese citizens and Chinese enterprises. (Thankfully, Canada is a little more open-minded in this regard.) Then there is the export control regime: Technologies that can be utilized to navigate ballistic missiles, to offer satellite-based navigation on the ground, and to perform remote sensing may be categorized as munitions and fall under export control restrictions in North America, with China specifically listed as a proscribed country.
The know-how (and software) that would be used to navigate the TianQin constellation is arguably subject to such restrictions at least on the first two counts, but possibly even the third: a precision interferometer in orbit can be used for gravitiational remote sensing, as it has been amply demonstrated by GRACE (Gravity Recovery And Climate Experiment), which was orbiting the Earth, and GRAIL (Gravity Recovery And Interior Laboratory) in lunar orbit. Then there is the Chinese side of things: precision navigation requires detailed information about the capabilities of tracking stations in China, which may be, for all I know, state secrets.
While these issues make things a little tricky for Western researchers, TianQin nonetheless has a chance of becoming a milestone experiment. I sincerely hope that they succeed. And I certainly feel honored, having been invited to take part in this workshop.
Hello, Guangzhou. And hello world, from Guangzhou. Here is what I see from my hotel window today:
It is a very interesting place. Today, I had a bit of a walk not just along the main urban avenues, full of neon and LED signs and modern high-tech stores, but also in some of the back alleys, complete with street vendors, stray dogs, and 60-70 year old crumbling buildings, some abandoned. In short… a real city with a real history.
For what it’s worth, I am here on account of a conference about a planned space-borne gravitational wave detector called TianQin.
Fourteen years ago, I embarked on a small hobby project: A compiler for an ultra-simple programming language I called W, a language specifically designed to produce short 16-bit DOS programs. It has the distinguishing characteristic of having neither keywords nor types. The only data type on which it operates is a 16-bit machine word (hence the name, W).
I then wrote a few pages about this language that are still featured on my Web site.
Today (not for the first time) my project was rediscovered. Apparently not everyone realized that this was an old project (I now changed the configuration of the project page to make sure its creation date is visible.) The link went a little viral, as it was featured on both Reddit and Y Combinator. Which explains why, when I woke up this morning, I saw my server under a far heavier load than usual.
It was interesting to look at the comments on these two sites. Some liked what I have done. Others were critical, not sure why; it was a hobby project, after all, I wasn’t trying to win any accolades. But there was one particular comment on Reddit, by user MarshallBanana, that I really liked:
“What a bastard, making something for himself for fun. He sure deserves some shit for that.”
Today, someone sent me a link to a YouTube video of an old Hungarian language television program that featured one of our Commodore 64 computer games, Save Me Brave Knight.
Except that the program featured a lot more than just the game: It also featured Viktor Zámbó and myself talking about the game. (I am second from the right; Viktor Zámbó is on the right.)
I remembered this program vaguely, but I couldn’t even recall its title. My past attempts to search for it were in vain; in fact, I doubted that it even made it online.
But here it is, the two of us, being interviewed at length (starting at 16:48) about the art and craft of game programming.
Wow.
I’m saving a copy of this video on the odd chance that it is removed or muted by YouTube for copyright reasons.
Here is a perfectly ordinary object. A paperclip.
But this particular paperclip has a bit of history.
It was attached to a typewritten document dating back to the early 1980s. It was written by some young Hungarian researchers who were entrusted with cataloging the manuscript collection of Hungarian Communist Politburo member Gyorgy Aczel. Aczel was arguably the best educated in the Politburo. He was also known as the architect the “three T-s” cultural policy of the goulash communist state. The T-s stood for “Trusted, Tolerated and Treasonous”. The second category represented works of art and literature that received no support from the state, but if they survived in the open market, they were tolerated and not censored. It was the existence of this category that allowed a cultural life in Hungary that was thriving relative to other East Bloc states.
As a young “star” programmer, I was asked to help this team with developing a manuscript database application (for the Commodore 64, no less). I was paid well, too. And on account of this assignment, I even met Mr. Aczel in person on one or two occasions. Yes, lucky me and all.
All of these are now memories from a distant past but somehow, one set of documents managed to stay with me inside a file folder over all these years. And yesterday, when I came across that folder, I decided to scan the sheets, and to do so, I removed this paperclip.
This paperclip was last handled by someone in 1984 or so, probably in the home of Mr. Aczel in the 13th district of Budapest, in a rental apartment building.
If only objects could speak and tell their stories.
I finished this weeks ago but never had the time to post. My previous attempt to hack a Rogers cable decoder was only partially successful, so I gave it another try, with better results.
By “hack”, I don’t mean illegally obtaining cable signals or anything like. I was simply looking for a way to get composite video and stereo audio out of the “free” cable boxes that Rogers provides, as opposed to just a plain RF signal on channel 3. The reason is pretty mundane: I’ve been using a dual-tuner TV card in my computer for years, which allowed me to record one program while watching another. The transition by Rogers to full digital cable messed this up: the TV card has only one RF input, so it is impossible to attach two decoders that could supply two signals simultaneously. But the TV card does have two independent composite video inputs. So if only the decoders had the corresponding output…
Well, they do, sort of: the only problem was that the audio was an undecoded (multiplexed) stereo signal. To decode it, I first built a standard stereo decoder circuit, but that was before I learned that the NTSC standard for stereo also includes noise suppression.
Hence my second attempt, using an appropriate chip.
Once again, I used a custom printed circuit board of my own design, and once again, it worked like a charm. The only fly in the ointment is that this larger board no longer fits inside the original decoder casing without some “plastic surgery”; so chances are that if it ever comes to returning these boxes to Rogers, I’ll be paying for them instead. Oh well.
Even as I hope that the wheels are indeed falling off Mr. Harper’s election bus, I am trying to do my part by listing more of the Harper government’s shenanigans on catsforharper.ca.
The idea is simple. Harper likes cats. He should have more time to play with cats. And he should atone for his political sins by adopting lots of shelter cats.
The site is growing, by the way; I still have a ways to go through my list of political sins so new topics are added daily, sometimes several times a day.
I am disappointed, however, with my Canadian friends: So few of you registered and “voted” on catsforharper.ca! I honestly hoped it would be more popular. But then, there is still time… 8 more days until Election Day. And I hope most sincerely that after October 19, I can safely retire the site, as Mr. Harper will no longer be in a position to do any more political damage.
I received a very polite invitation to be an “academic editor” to a scholarly journal.
Sounds good, right? To be sure, I am promised no monetary compensation, indeed, I’d still have to pay (albeit at a discount) to have my papers published in the same journal (not that I have any plans to do so). Still… it’s an honor, right?
Too bad it’s one of the many predatory journals of a predatory publisher. A journal that publishes just about anything so long as the author pays the (often hefty) publication fee. There are now thousands of such journals around the world, maintaining a parasitic existence, leeching off both crackpots and third-world researchers who don’t know any better and try to pad their resumes with a seemingly legitimate publication record.
So why am I ever so slightly hesitant? Well… on two (maybe three?) occasions in recent weeks, I received requests from the same journal to referee papers. I indicated that I was not available, but also that, judging by the abstracts that were shared with me, those papers should have been rejected by the editor and never sent out to referees in the first place.
And now here I am, being asked to work as a volunteer editor for the same journal. Should I accept it, in the hope that I would be given the editorial autonomy to reject papers up front, in the hope of improving the journal’s standards?
Probably a bad idea.