Nov 082023

Sometimes it feels… so pretentious.

Here I am, saying all sorts of clever things in my blog. I once declared blogs to be write-only media, my way of shouting at the world without the world saying anything in return, but that kind of ceased being true when I decided, eons ago, to share my blog posts on social media, where a few friends at least reacted occasionally.

So who do I think I am, proclaiming my wisdom to the world, really?

For instance, a few days ago I thought I’d blog about the first precision clock arriving in America centuries ago, and promptly failing, leading to a better understanding of how the gravitational acceleration on the surface of the Earth may change with geographic location. But is there anything I can add to the subject other than what’s in the article I am citing?

Or take this report from earlier today, about Singapore’s Prime Minister expressing very much the same concerns that I have about the world experiencing a moment of danger not unlike the moments before the Great War. OK, so I blog about it. Is there anything I can add other than, hey, look, I am ever so clever, even Singapore’s PM shares my views!?

I suppose I feel most comfortable blogging about my actual research or my work. These are subjects that I can address with some competence.

Or maybe just blog about cats. They know how to be wise and silent, after all.

Meanwhile, in the world of humans…

F-15s strike weapons facility in Syria

By Lauren C. Williams and Jennifer Hlad

ABOARD A MILITARY PLANE—Two U.S. F-15 fighter jets attacked a weapons storage facility in eastern Syria on Wednesday, in what Defense Secretary Lloyd Austin called a “precision self-defense strike” in response “to a series of attacks against U.S. personnel in Iraq and Syria by the [Iranian Islamic Revolutionary Guard Corps]-Quds Force” and related groups.

So I must now follow my cats’ example and resist the urge to blog about how the US and Iran might already be at war…

 Posted by at 9:51 pm
Nov 012023

A few minutes ago, I checked Google News on my phone and lo and behold, there was a link to Universe Today, a new article discussing my latest manuscript on multiple gravitational lenses.

I knew that this was in the works, as the author approached me with some questions earlier in the day, but I didn’t expect it to appear this quickly, and, well, seeing it on my phone like this was a nice surprise.

Had the author asked, I’d have happily granted permission to use one of my generated images or animations involving multiple lenses.

Meanwhile, my paper on a four-satellite configuration used to detect deviations from Newtonian gravity was published by Astrophysics and Space Science, one of the Nature journals. I am officially permitted (in fact, encouraged) by Springer to share the link to an online read-only version of the published paper.

 Posted by at 1:25 am
Oct 122023

I’m doing more work on gravitational lensing. In particular, the little ray tracing model that I developed can now use actual astronomical images as sources. Here’s a projection of a nice spiral galaxy as it would be seen through a pair of non-coplanar, imperfectly lined up lenses:

Somehow, I suspect, no astronomer would recognize (at least not without a spectral analysis) that these are four images of the same rather nice-looking galaxy, NGC-4414:

These lensing examples also demonstrate how difficult it is to reconstruct either the original view, or the mass distribution of the lens itself, when all we see is something like the first image above.

 Posted by at 9:35 pm
Oct 082023

I am simulating gravitational lenses, ray tracing the diffracted light.

With multiple lenses, the results can be absolutely fascinating. Here’s a case of four lenses, three static, a fourth lens transiting in front of the other three, with the light source a fuzzy sphere in the background.

I can’t stop looking at this animation. It almost feels… organic. Yet the math behind it is just high school math, a bit of geometry and trigonometry, nothing more.

NB: This post has been edited with an updated, physically more accurate animation.

 Posted by at 5:35 pm
Oct 052023

I don’t know much about attosecond light pulses but my wife and I did note that one of the recipients of this year’s physics prize was a physicist who studied just a year ahead of Ildiko at ELTE (Eötvös University). She doesn’t recall if she ever bumped into Ferenc Krausz, though.

And of course one of the recipients of the Nobel prize in physiology or medicine was Katalin Kariko, for her groundbreaking work in mRNA vaccines. Well-deserved indeed! I actually know (a little bit) more about mRNA vaccines than about attosecond physics, which might seem odd, considering that physics is my home turf, and organic chemistry is like an alien landscape. But the generation of ultrashort photon pulses is a very specialized field of study, to which I never paid much attention.

Anyhow, Kariko and Krausz are now added to that long list of scientists who were born, and studied in, Hungary, but who eventually ended up abroad, where they did the bulk of the work that earned them this recognition.

 Posted by at 7:03 pm
Oct 032023

Here’s my phone screen as of a few minutes ago:

That’s in Centigrade of course.

What can I say? OK, our balcony thermometer only shows 28.3 C. Even so… not exactly typical early October weather for Ottawa.

 Posted by at 5:08 pm
Sep 292023

I’ve been meaning to mention this: A few days ago, the sample capsule of the OSIRIS-REx mission returned safely to the Earth, carrying inside a sample taken from the asteroid Bennu.

This is a remarkable achievement, the first* successful sample return of its type. I wonder what we will learn from the material that was obtained, but I’m sure it will reveal some intriguing secrets, especially about the history and formation of the solar system.

Love the way the capsule was sitting on the ground, upright, not even tilted. Could it be more picture perfect than this?

I am also mildly (but pleasantly) surprised that I have not heard any panicmongering about a capsule bringing back extraterrestrial microbes or whatever. OK, I wasn’t specifically looking but still. It’s a relief.

* I don’t know what possessed me when I wrote “first”; granted, OSIRIS-REx brought back a lot more material, supposedly, but the first successful such missions were the two Hayabusa missions of the Japanese Space Agency.

 Posted by at 6:09 pm
Sep 292023

OK, not exactly a surprising result but still, a fantastic experimental achievement: Yes, Virginia, antimatter falls downward.

Why is this important? Well, we kind of knew that it was inevitable. I mean, if antimatter were to fall upward, it’d have meant that our entire understanding of gravitation is wrong. That even our understanding of special relativity is probably wrong.

So it was a rather safe bet that antimatter follows the same geodesics as normal matter and falls downward.

But physics, lest we forget it, is ultimately not about erudite speculation. It is about experiment and observation.

And this amazing experiment achieved the almost impossible: it observed antihydrogen atoms in a vertical vacuum chamber at cryogenic temperatures and, as expected, most of those hydrogen atoms ended up at the bottom.

 Posted by at 12:33 am
Sep 162023

My friend John Moffat has a finite quantum field theory that, I think, deserves more attention than it gets.

The theory is nonlocal (then again, so is quantum physics to begin with). However, it does not violate causality. So its nonlocality is a mathematical curiosity, not a physical impossibility.

The essence of the theory is present in the form of its “nonlocal field operator”. Given, e.g., a scalar field in the form \(\phi(x),\) the field is transformed as

$$\tilde\phi(x)=\int d^4x’f(x-x’)\phi(x’).$$

Now if we just used the Dirac delta-function \(f(x-x’)=\delta^4(x-x’),\) we’d get back \(\phi(x).\) But what if we use some other function, the only restriction being that \(f(x)\) must be an entire function, which is to say, unambiguously defined without poles or singularities over the entire complex plane?

Well, then, assuming again that \(f(x)\) is an entire function, we can integrate iteratively in parts, until we arrive at an expression in the form,

$$\tilde\phi(x)={\cal F}(\partial_x)\phi(x),$$

where \({\cal F}(\partial_x)\) is a derivative operator, typically some power series in the form \(\lambda_i\partial_x^i\), acting on \(\phi(x).\)

Why is this good for us? Because this field redefinition can suppress high-energy divergences in the theory, essentially doing away with the need for renormalization, which, of course, is a Big Claim indeed but I think John’s theory works.

John’s first substantive papers on this topic were titled Finite quantum field theory based on superspin fields (J. W. Moffat, Phys. Rev. D 39, 12 (1989)) and Finite nonlocal gauge field theory (J. W. Moffat, Phys. Rev. D 41, 4 (1990)). Unfortunately these papers predate so only the paywalled versions are available. They are beautiful papers that deserve more recognition. More recently, John wrote another paper on the subject, collaborating with a student. One of these days, I’m hoping to spend some time myself working a bit on John’s theory because I believe it has merit: The theory appears to remain causal despite the nonlocal operator, and by doing away with the need for renormalization, it makes canonical quantization almost trivially possible. I keep wondering if there is, perhaps, a catch after all, but if that’s the case, I have yet to find it.

 Posted by at 1:37 pm
Sep 122023

I gave a talk on the Solar Gravitational Lens in Montreal back in July, using the above title.

Video of the talk is now available online, courtesy of the Interstellar Research Group.

I just listened to it myself and I didn’t cringe too much hearing my own voice or watching myself, which is probably a good sign?

 Posted by at 12:31 am
Aug 232023

Chandrayaan-3 landed safely on the Moon, cementing India’s position as a space superpower.

What can I say? Congratulations! Not sure who the gentleman is in this image that I saw on Twitter, but he certainly looks happy.

 Posted by at 12:48 pm
Aug 212023

Russia’s first probe to the Moon in nearly half a century, Luna-25, has crashed.

It would be easy to react to the news with glee, with schadenfreude. We are, after all, talking about a crash that denied a propaganda opportunity to Putin’s Evil Empire (maybe not quite as evil as Stalin’s regime but more evil, to be sure, than the USSR ever was in my lifetime).

But space exploration transcends, always transcended, national boundaries. Our petty squabbles look pretty… well, petty from the Moon. Chances are, if human beings are still around with an advanced technical civilization a millennium from now (or, if our machine descendants are still around) they’re far more likely to remember Armstrong’s first step on the Moon than Russia’s attack on Ukraine, the Cold War, or even WW2.

So this crash is sad news, Putin or no Putin. I hope India’s probe, Chandrayaan-3, is more successful. Fingers crossed. Things are looking good for now but it has yet to accomplish a tricky landing.

 Posted by at 11:57 pm
Aug 182023

And then there is this. The rate of increase in atmospheric methane has been rising since the mid-2000s. The curve is becoming ever steeper.

Surprisingly perhaps, it’s not from natural gas producers, industry, or vehicles. Not even cow farts.

It’s apparently in large part coming from tropical wetlands. Climate change is still indirectly responsible as it is the changing climate that changes the vegetation that, in turn, results in more methane production. But the consequences of this rise in methane levels can dwarf anything CO2 will do. A “termination-level” event, they call it, which sounds alarming and it should be: even though it does not mean our immediate termination, it may mark the termination of an epoch, just as in the past, when similar rises in methane events marked the end of the ice ages. Except that there’s no ice age at present.

 Posted by at 5:47 pm
Aug 182023

Yellowknife is not a large city by Ontario standards, but it is the capital city and the largest community in the Northwest Territories of Canada, with over 20,000 inhabitants.

And it is about to be evacuated entirely today, because of the imminent wildfire threat.

Yes, it’s a faraway place but it is still incredibly scary that tens of thousands of Canadians are uprooted, some taking their cars, some boarding evacuation buses or flights, fleeing their homes, traveling through landscapes that are like warzones, with burned buildings and burnt-out vehicles often in sight.

No, I won’t rant about climate change. There can be other contributing reasons behind this unprecedented wildfire season, though I bet climate change is by far the most significant contributor.

I wonder what prompted N.W.T. authorities to take this drastic step. I may be wrong but I have a feeling that the devastation in Maui was a wake-up call, and they wanted to avoid a similar disaster. Having said that, I sincerely hope that Yellowknife will be spared and its inhabitants can return in a few days.

 Posted by at 2:43 am
Aug 112023

Here’s a sunflower, which grew in a large planter right here on our driveway, as photographed by my beautiful wife just the other day (before Ottawa got an incredible deluge of rain):

If you look closely, there’s a bumblebee in the flower. May there be more! I keep reading about the crisis pollinating insects face worldwide, sometimes accompanied by tragic images of entire beehives, dead. Pollinating insects play an essential role in nature, including our food supply. And they seem to be in serious trouble. Climate change, habitat loss, reckless use of insecticides, whatever the reason, it might be a good idea to take this problem seriously before it is too late. (Just don’t turn it into politics please. It’s a real crisis, not fodder for virtue-signaling by wannabe liberals or progressive-bashing by wannabe conservatives.)

 Posted by at 5:38 pm
Aug 062023

I don’t usually like climate panicmongering but this chart that I came across today is… Well, see for yourself.

These are ocean temperatures, by the way. Oceans are supposed to be large, stable reservoirs of heat. Which they probably are, except that surface temperatures also reflect changing patterns like changing ocean currents.

This massive deviation from the 20+ year average (more than four sigmas!) is difficult to comprehend. What it says about the changing climate, I have no idea, but it is unlikely to be good news.

If only we stopped making this political. OK, well, it is of course political in the sense that we need to make collective, i.e., political decisions on how we manage Spaceship Earth. But it should not be political in the sense that the facts are not political, and the proposed solutions should be weighed by their feasibility, efficacy and social impact, not political palatability.

And for heaven’s sake, stop the dumbed down oversimplifications. Next time I hear about someone emitting “carbon”, I’ll scream. Carbon is solid at room temperature. Carbon is not carbon dioxide, just as hydrogen is not dihydrogen oxide. I have yet to see anyone drinking liquid hydrogen… or emitting carbon. Perhaps the first step to take is to give people a more decent education in the sciences so that they actually understand what carbon dioxide is, what it does in the atmosphere, what “four sigma” means, and what things like heat reservoirs are in a climate system? Is that really too much to ask? Am I being a silly elitist or something?

 Posted by at 7:59 pm
Jun 262023

The next time (it happens often) I hear someone complain about scientific ‘orthodoxy’ that is used to ‘stop innovation’ and prevent ‘new entrants from entering’ the field (or equivalent words), I’ll remind them that these were exactly the words used by Stockton Rush, defending the design of his ill-fated submersible Titan.

Of course the consequences are far less deadly when the subject is purely theoretical, like fundamental particle physics or general relativity. But that does not validate nonsensical arguments.

Orthodoxy is adherence to tradition or faith. Science and engineering are about testable and tested knowledge, which is the exact opposite. What folks like Stockton describe as orthodoxy is simply knowledge that they do not possess (maybe because it takes too much of an effort to learn) or knowledge they purposefully ignore because it contradicts their preconceptions or expectations.

My condolences to the families of Rush and his passengers on Titan. But foolishness has its consequences. Sometimes deadly ones.

 Posted by at 10:33 am
May 312023

I just finished uploading the latest release, 5.47.0, of our beautiful Maxima project.

It was a harder battle than I anticipated, lots of little build issues I had to fix before it was ready to go.

Maxima remains one of the three major computer algebra systems. Perhaps a bit (but only a bit!) less elegant-looking than Mathematica, and perhaps a bit (but only a bit!) less capable on some friends (exotic integrals, differential equations) than Maple, yet significantly more capable on other fronts (especially I believe abstract index tensor algebra and calculus), it also has a unique property: it’s free and open source.

It is also one of the oldest pieces of major software that remains in continuous use. Its roots go back to the 1960s. I occasionally edit 50-year old code in its LISP code base.

And it works. I use it every day. It is “finger memory”, my “go to” calculator, and of course there’s that tensor algebra bit.

Maxima also has a beautiful graphical interface, which I admit I don’t use much though. You might say that I am “old school” given my preference for the text UI, but that’s really not it: the main reason is that once you know what you’re doing, the text UI is simply more efficient.

I hope folks will welcome this latest release.

 Posted by at 8:54 pm
May 232023

In the last several years, we worked out most of the details about the Solar Gravitational Lens. How it forms images. How its optical qualities are affected by the inherent spherical aberration of a gravitational lens. How the images are further blurred by deviations of the lens from perfect spherical symmetry. How the solar corona contributes huge amounts of noise and how it can be controlled when the image is reconstructed. How the observing spacecraft would need to be navigated in order to maintain precise positions within the image projected by the SGL.

But one problem remained unaddressed: The target itself. Specifically, the fact that the target planet that we might be observing is not standing still. If it is like the Earth, it spins around its axis once every so many hours. And as it orbits its host star, its illumination changes as a result.

In other words, this is not what we are up against, much as we’d prefer the exoplanet to play nice and remain motionless and fully illuminated at all times.

Rather, what we are against is this:

Imaging such a moving target is hard. Integration times must be short in order to avoid motion blur. And image reconstruction must take into account how specific surface features are mapped onto the image plane. An image plane that, as we recall, we sample one “pixel” at a time, as the projected image of the exoplanet is several kilometers wide. It is traversed by the observing spacecraft that, looking back at the Sun, measures the brightness of the Einstein ring surrounding the Sun, and reconstructs the image from this information.

This is a hard problem. I think it is doable, but this may be the toughest challenge yet.

Oh, and did I mention that (not shown in the simulation) the exoplanet may also have varying cloud cover? Not to mention that, unlike this visual simulation, a real exoplanet may not be a Lambertian reflector, but rather, different parts (oceans vs. continents, mountain ranges vs. plains, deserts vs. forests) may have very different optical properties, varying values of specularity or even more complex optical behavior?

 Posted by at 12:06 am
May 052023

I got sent a link about an interesting, newly published book on the memoirs of Charles-Augustin de Coulomb. He was, of course, the French officer, engineer and physicist most famous for the Coulomb law that characterizes the electrostatic interaction.

As I occasionally receive e-mails from strangers about their self-published tomes or tomes published through vanity publishers of questionable credibility, I have come to the habit of dismissing such e-mails without paying them much attention. I am glad I paid more attention this time because this book is interesting, valuable, and genuine.

It is available as a matter of fact as a free PDF download from the authors but hey, I just bought the paperback. It was for some reason deeply discounted on Amazon Canada, so with free Prime shipping, all I am paying is the princely sum of $3.15. These days when even “cheap” paperback novels often cost 20 bucks if not more, how could I resist?

Of course it also helped that I looked at the PDF. I am sure the book has flaws (all books do) but it looks like a serious scholarly publication delivering real value to physicists and science historians both.

In fact, it is fascinating to see how modern, how advanced scientific thinking was already evident more than a quarter millennium ago. It makes me appreciate even more just how much of our collective human effort was needed to get from these early experiments to the present era of ubiquitous computer networks running amazing software that now mimics human intelligence, all powered by the same electricity that Coulomb was exploring.

 Posted by at 9:46 pm