Stephen Hawking passed away over a month ago, but I just came across this beautiful tribute from cartoonist Sean Delonas. It was completely unexpected (I was flipping through the pages of a magazine) and, I admit, it had quite an impact on me. Not the words, inspirational though they may be… the image. The empty wheelchair, the frail human silhouette walking away in the distance.
This stunning young lady is none other than future First Lady of the United States, Barbara Bush, back in 1943.
Alas, Barbara Bush is no more. She passed away today after a prolonged illness.
She was genuine, she was funny, and she was noble. Her husband for more than 70 years, George H. W. Bush and Barbara Bush were clearly a loving couple until the very end.
And she even appeared on The Simpsons.
May she rest in peace.
Our oldest cat Kifli just turned 17.
One more year and he’ll be eligible to vote.
Well, that would be Victor Gabriel Toth, not me, but nonetheless, it is still creepy to see an obituary in the Ottawa Citizen containing, albeit with a minor spelling variation, my name.
I never met this Victor Toth, even though at one point, I was told, I might have been working just two floors above him at the Nortel building on Merivale Road, a building in which several floors were rented by Canada Post.
Well, Victor Toth, you had a long life and, I hope sincerely, a happy one. I hope your family is not so much grieving as celebrating your long life.
Then again, I also sincerely hope that I won’t be following in your footsteps anytime soon, as I have plenty more to do in this world before it’s my time to depart.
Yesterday, we said goodbye to our old car, a very nice Honda Accord that served us faithfully for four years.
The lease expired, so we opted to lease a new one. Another Honda Accord. (Incidentally, 2018 marks the 30th year that I’ve been purchasing Hondas, from this very same dealership.)
The old car was nice. The new car… Well, it’s amazing what even four years can mean these days when it comes to vehicle automation.
The level of automation in this vehicle is amazing. It can start itself, it can steer itself. It has full situational awareness, with radar all around. Apparently, it even monitors the driver for alertness (I’ll have to read up on exactly how it accomplishes that.) During the short drive home, it once applied the brakes when its adaptive cruise control was on and someone moved into the lane ahead of us. It was braking a little harder than I’d have preferred, though. And at one point, as the lane markings were a little ambiguous, it gently resisted my attempt to depart from what it thought was the correct lane.
In principle, it appears, this car has all the components for it to be fully autonomous, except that perhaps its array of sensors is not sufficient for it to be fully safe. But really, the only thing missing is the software. And even the way it is, it is beginning to feel more like a partner in driving than a dumb machine; a partner that also has a well-developed instinct for self-preservation.
Welcome to the future, I guess.
What can I say?
Shit. Hitting. Fan.
A couple of statements from the past 24 hours:
“If there is a strike by the Americans, then…the missiles will be downed and even the sources from which the missiles were fired.” – Russian Ambassador to Lebanon Alexander Zasypkin, on Hezbollah’s al-Manar TV.
“Russia vows to shoot down any and all missiles fired at Syria. Get ready Russia, because they will be coming, nice and new and “smart!” You shouldn’t be partners with a Gas Killing Animal who kills his people and enjoys it!” – United States president Donald J. Trump, on Twitter.
Suddenly, I have this almost irresistible urge to grab a shovel and start digging a fallout shelter.
While I still can.
A headline on Euronews caught my attention earlier today: Syria: A bigger role for the EU?
Good, thought I. The Russians might not like it though, thought I. But that’s okay, as a matter of fact, it might help bring rogue EU countries like Hungary in line, thought I. It might help presenting a united front against an increasingly ill-behaved Russia.
And then I caught myself, as I realized that I just rediscovered a truth that is as old as civilization itself: how conflict, the threat of war, or war itself can unite a people.
You know what? Much as I like the great European experiment, much as I cherish the fact that my once worthless Hungarian passport grants me European citizenship, if the price of keeping it together is more involvement in conflicts like Syria, it might not be worth it.
The recent discovery of a galaxy, NGC1052-DF2, with no or almost no dark matter made headlines worldwide.
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| Nature 555, 629–632 (29 March 2018) |
Somewhat paradoxically, it has been proclaimed by some as evidence that the dark matter paradigm prevails over theories of modified gravity. And, as usual, many of the arguments were framed in the context of dark matter vs. MOND, as if MOND was a suitable representative of all modified gravity theories. One example is a recent Quora question, Can we say now that all MOND theories is proven false, and there is really dark matter after all? I offered the following in response:
First of all, allow me to challenge the way the question is phrased: “all MOND theories”… Please don’t.
MOND (MOdified Newtonian Dynamics) is not a theory. It is an ad hoc, phenomenological replacement of the Newtonian acceleration law with a simplistic formula that violates even basic conservation laws. The formula fits spiral galaxy rotation curves reasonably well, consistent with the empirical Tully—Fisher law that relates galaxy masses and rotational velocities, but it fails for just about everything else, including low density globular clusters, dwarf galaxies, clusters of galaxies, not to mention cosmological observations.
MOND was given a reprieve in the form of Jacob Beckenstein’s TeVeS (Tensor—Vector—Scalar gravity), which is an impressive theoretical exercise to create a proper classical field theory that reproduces the MOND acceleration law in the weak field, low velocity limit. However, TeVeS suffers from the same issues MOND does when confronted with data beyond galaxy rotation curves. Moreover, the recent gravitational wave event, GW170817, accompanied by the gamma ray burst GRB170817 from the same astrophysical event, thus demonstrating that the propagation speed of gravitational and electromagnetic waves is essentially identical, puts all bimetric theories (of which TeVeS is an example) in jeopardy.
But that’s okay. News reports suggesting the death of modified gravity are somewhat premature. While MOND has often been used as a straw man by opponents of modified gravity, there are plenty of alternatives, many of them much better equipped than MOND to deal with diverse astrophysical phenomena. For instance, f(R) gravity, entropic gravity, Horava—Lifshitz gravity, galileon theory, DGP (Dvali—Gabadadze—Porrati) gravity… The list goes on and on. And yes, it also includes John Moffat’s STVG (Scalar—Tensor—Vector Gravity — not to be confused with TeVeS, the two are very different animals) theory, better known as MOG, a theory to which I also contributed.
As to NGC1052-DF2, for MOG that’s actually an easy one. When you plug in the values for the MOG approximate solution that we first published about a decade ago, you get an effective dynamical mass that is less than twice the visible (baryonic) mass of this galaxy, which is entirely consistent with its observed velocity dispersion.
In fact, I’d go so far as to boldly suggest that NGC1052-DF2 is a bigger challenge for the dark matter paradigm than it is for some theories of modified gravity (MOG included). Why? Because there is no known mechanism that would separate dark matter from stellar mass.
Compare this to the infamous Bullet Cluster: a pair of galaxy clusters that have undergone a collision. According to the explanation offered within the context of the dark matter paradigm (NB: Moffat and Brownstein showed, over a decade ago, that the Bullet Cluster can also be explained without dark matter, using MOG), their dark matter halos just flew through each other without interaction (other than gravity), as did the stars (stars are so tiny compared to the distance between them, the likelihood of stellar collisions is extremely remote, so stars also behave like a pressureless medium, like dark matter.) Interstellar/intergalactic clouds of gas, however, did collide, heating up to millions of degrees (producing bright X-rays) and losing much of their momentum. So you end up with a cloud of gas (but few stars and little dark matter) in the middle, and dark matter plus stars (but little gas) on the sides. This separation process works because stars and dark matter behave like a pressureless medium, whereas gas does not.
But in the case of NGC1052-DF2, some mechanism must have separated stars from dark matter, so we end up with a galaxy (one that actually looks nice, with no signs of recent disruption). I do not believe that there is currently a generally accepted, viable candidate mechanism that could accomplish this.