The Perimeter Institute turned into a major construction zone. But, it’s still fun to be here. And useful… I work very well with people over the Internet and the telephone, but some difficult issues are better discussed face-to-face.
Jan 282010
Jan 222010
Here’s a nice tennis ball, photographed from both sides:
It’s a big one, mind you, almost a thousand miles across. It’s Saturn’s moon Iapetus, famous because one side of it is significantly brighter than the other. The explanation, however, is more mundane than that offered in the book version of Clarke’s 2001: A Space Odyssey; the most recent hypothesis is that the discoloration is due to the thermal migration of ice.
Jan 222010
Wow. It took a long time (we’ve been working on this thing since 2007!) but the draft of our big Pioneer Anomaly review paper is finally out there.
Jan 212010
Just when you thought Climategate was bad enough already, here’s another little tidbit.
Back in 1999, New Scientist published an interview with Indian climate scientist Syed Hasnain about melting glaciers in the Himalayas. In this interview, Hasnain speculated that “all the glaciers in the central and eastern Himalayas could disappear by 2035 at their present rate of decline”.
Fast forward to 2007 and the (in)famous Intergovernmental Panel on Climate Change report, which states that “Glaciers in the Himalaya are receding faster than in any other part of the world and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at the current rate.” The source? A 2005 report by the World Wildlife Fund, which, in turn, quotes the New Scientist: “The New Scientist magazine carried the article ‘Flooded Out – Retreating glaciers spell disaster for valley communities’ in their 5 June 1999 issue. It quoted Professor Syed Hasnain, then Chairman of the International Commission for Snow and Ice’s (ICSI) Working Group on Himalayan Glaciology, who said most of the glaciers in the Himalayan region ‘will vanish within 40 years as a result of global warming’. The article also predicted that freshwater flow in rivers across South Asia will ‘eventually diminish, resulting in widespread water shortages’.”
So, it appears that a popular science magazine was the primary source for such a dramatic statement. The assertion that Himalayan glaciers might disappear by 2035 was never published in a peer reviewed journal. Worse yet, note how the statement became inflated over time: whereas the original article spoke of “all the glaciers in the central and eastern Himalayas”, the WWF translated this into “most of the glaciers in the Himalayan region”, and by the time this gloomy prediction got into the IPCC’s report, it read simply, “”Glaciers in the Himalaya”.
Now New Scientist is taking them to task, leaving many to wonder: is this really representative of the quality of the science on which dire global warming predictions are based?
For the record, while glaciers in the Himalayas may suffer from global warming, they’re not (yet) in danger of disappearing anytime soon. Certainly not by 2035.
Jan 122010
I just finished a neat little paper with John Moffat. Jordan-Brans-Dicke theory is a generalization of relativity theory, in which the gravitational constant becomes variable, and the resulting (scalar) field has kinetic energy. First described by Pascual Jordan in his 1952 book Schwerkraft und Weltall, it was perhaps the first serious, “modern” modification of Einstein’s gravity. Yet it is rejected in the solar system, because it predicts an observable parameter that is grossly out of whack with observation. Then again… in the original form, the scalar field arises as a result of changes in spacetime curvature, only indirectly responding to the presence of matter. If we add matter as a direct source, the picture changes. Even more interesting, if matter and curvature kind of cancel each other out, we get a (still variable, still dynamical) scalar field that’s just like a field in vacuum, and agreement with solar system observations is restored.
Incidentally, Pascual Jordan was one of the greatest 20th century German physicists. Unfortunately he was also an ardent Nazi, member of the NSDAP and an SA volunteer. This may have been the reason why he never received the Nobel prize. Goes to prove that politics and science are really not a very good mix.
Jan 012010
This is the year when the Soviet spaceship Alexei Leonov was supposed to fly to Jupiter, investigating the failure of the spaceship Discovery and the death of her crew nine years earlier. At least in one respect, Clarke’s vision will come true: after the Space Shuttle’s planned retirement later this year, the United States will be left without a manned launch capability, and American astronauts will be ferried to the International Space Station (alas, a mere few hundred kilometers above the Earth’s surface, not a billion kilometers from here like Jupiter) on board Russian spacecraft. Not exactly an inspiring thought, except perhaps to some Russians.
Dec 292009
There is a fascinating book published by the RAND Corporation, available at Amazon for a mere 81 US dollars. I am tempted to buy it. It must be a fascinating read. Readers’ comments at Amazon are certainly encouraging; while the book has some minor flaws, despite the lack of serious proofreading it is guaranteed not to contain any errors, and it helped at least one reader get to meet the woman who eventually became his wife.
Dec 172009
I’m reading an opinion piece in last week’s New Scientist, by Michael Le Page and Catherine Brahic. It’s titled, “Why there’s no sign of a climate conspiracy in hacked emails”. It is intended to reassure us that “Climategate” notwithstanding, we should trust the basic science. Yet I feel that it misses the point on all counts.
Take the title, for starters. While I am sure there are conspiracy nuts out there who view the hacked e-mails as a smoking gun, I think many more people see a more nuanced picture: the e-mails prove no conspiracy, but they do demonstrate contempt towards dissenters and the general public, not to mention the scientific process, and they do raise questions about the validity of the so-called “scientific consensus” on climate.
But it’s not just the title that’s deceptive. The authors raise five points, in the form of questions and answers. At least that’s how the article appeared in print; on-line, two of the questions were turned into unambiguous statements, according to which we are “100% sure” that the world is getting warmer and it’s because of greenhouse gases as the main cause. No, we are not 100% sure. If you want to assign a percentage, then take the data, fit the models, and show us a covariance matrix that tells us exactly how sure we are that a long-term trend is present. Leave this “100%” nonsense to political activists.
The print edition stuck to the question-and-answer form. “How can we be sure that the world really is warming?” they ask, but it’s a misleading question: of course the world is warming, the real question is, how much of that warming is due to short/medium/long term natural periodicities, and how much of it is due to a more sudden (e.g., linear, exponential, etc.) trend that may be due to human activity. Do we have enough data to distinguish unambiguously (never mind 100%, 1-sigma can do nicely) natural fluctuations from more direct trends?
Then they ask, “How do we know greenhouse gases are the main cause?”, and assure as that “The physics is clear: carbon dioxide is a greenhouse gas, greenhouse gases warm the atmosphere, and CO2 is accumulating in the atmosphere.” This is pure nonsense of course, since I could just as well say something like, “urine is a liquid, adding a liquid to the oceans increases ocean volume, I keep peeing into the ocean, hence cities will be swallowed by rising sea levels”. Their answer sounds more like an attempt to divert attention away from genuine questions, such as those concerning the effectiveness of CO2 as a greenhouse gas (CO2 is a very weak greenhouse gas; for instance, if rising CO2 levels somehow reduced the amount of water vapor in the atmosphere, the net effect would be global cooling), the accuracy of models describing the effects of CO2 in the atmosphere (I’ve read a paper, for instance, that questions the ability of widely used physics models to deal properly with the discontinuity of the atmosphere-surface boundary), or the “chicken-and-egg” question concerning the climate record, namely the extent to which CO2 caused warming trends or rising temperatures caused an increase in CO2 during past warm periods.
Their third question reads, “So why are scientists ‘fixing’ temperature data?”, which they answer by explaining that raw data almost always has to be manipulated to correct measurement problems or reconcile measurements made in different ways. True. But that is no excuse to discard the raw data. Not to mention that the data manipulation that caught so many people’s attention in the Climategate e-mails was not about fixing up raw data… it was about using two incompatible sets of data to change the appearance of a fitted curve, lest it gives the wrong impression to a scientifically illiterate audience. They do address this issue separately in the on-line version, but the explanation they offer raises its own questions: for instance, they say that “there has been no attempt to conceal this”, but how does that reconcile with the phrase, “hide the decline”, quoted from the hacked e-mails?
Lastly, their final two questions are about the attempts to suppress skeptical papers and attempts to prevent data from being released. We’re told that an independent inquiry is still ongoing, and in any case, the scientists may not have had the right to release the data. That’s a non-answer. You don’t need an independent inquiry to explain how it is acceptable to “redefine the peer review process” just to keep skeptical papers out, and as to the data, how about answering the question insofar as it concerns data that they did have the right to release?
All in all, I could have come up with much better arguments myself… instead of attempting to side-step the questions, I’d have tried to address them. Data were manipulated because a fit indeed gave a curve that would give the wrong impression to the uninitiated, and adding the instrumental data to the fossil temperature record seemed like an honest “trick” to avoid this. Skeptical papers were suppressed because those involved may genuinely believe in their science, may genuinely believe that many of the skeptics are motivated by something other than pure scientific curiosity (especially if they happen to be financed by, say, a friendly neighborhood oil company), and may genuinely believe that we just don’t have time for this nonsense while the planet is heading towards a global disaster. Data were withheld because otherwise, all the time in the world would not be enough to deal with clowns who take that data, ignorantly (or nefariously) manipulate it, and come up with nonsense conclusions. These explanations may not justify the actions taken, but they might be closer to the truth in the end… and supposedly, truth and integrity are the only real currencies that science has at its disposal. Currencies which will be needed badly in the coming decades, in order to convince the inhabitants of Earth not to trash their planet beyond repair… regardless whether or not CO2 leads to global warming.
Dec 072009
41,000 tons of CO2 is the amount of “CO2 equivalent” that the Copenhagen climate summit is expected to produce. No, it’s not the amount produced by Switzerland in a year, even though CNN’s Jack Cafferty said so, probably missing the phrase, “thousands of” in the column heading of Wikipedia’s statistics. But it IS the amount of CO2 some smaller or less developed countries, e.g., Slovenia, Lithuania, or Kenya produce in a day. Another way of looking at it is that during its 12 days, the climate summit will be responsible for about 0.004% of the entire world‘s CO2 output.
No need to worry, I am sure there is a neat “trick” that can be used to “hide” this embarrassing little data point, too, lest it dilutes the message about the coming climate disaster.
Nov 252009
I’m still trying to digest this… the meaning of recently released e-mails that suggest, to put it mildly, questionable behavior on behalf of some of the world’s leading climate researchers.
One e-mail that’s most hotly debated is about this:
This plot contains two types of data: long-term reconstructed temperatures from the fossil record, and shorter term instrumental temperatures. Now the trouble is, the smoothed curve (green) based on the reconstructed temperatures alone points slightly downward… no dramatic warming trend. In contrast, the instrumental temperatures show an upward trend. This apparent disagreement is purely a mathematical artifact; anyone who ever attempted to fit, for instance, a polynomial curve to some data knows that the fit tends to diverge near the ends of the data interval. But it wouldn’t look good on a report that is designed to influence world opinion and global policy to show a downward trend, would it. So there’s a neat “trick”: the apparent downward trend can be eliminated by using the instrumental temperatures to pad the reconstructed temperature data set, and produce an upward trend.
Note that this doesn’t mean that there is a downward trend. The planet may very well be warming, due to what people are doing to it. Unfortunately, the information content of manipulated graphs is zero, or less than zero even… they can generate skepticism towards genuine future results and delay a necessary public response.
There are many other questionable e-mails in the lot, including e-mails that suggest the hiding of data from freedom-of-information requests, e-mails that suggest efforts to block the publication of research by climate change skeptics, and at least one eyebrow-raising comment cheering at the death of a climate change skeptic, leading to calls for a researcher to resign.
I’m still digesting this, but it reinforces my conviction that phrases like “standard model” or “scientific consensus”, far from reassuring, should be a clear indication that the science might be shaky, and that an attempt is being made to substitute authority in place of convincing data and firm logic.
Nov 132009
Unlucky Friday the 13th it is not, at least not for NASA; they just announced that the much maligned LCROSS impact mission has, after all, found water on the Moon.
Does this mean that I might yet live long enough to see a permanent manned lunar base come into existence?
Nov 032009
Some Romanians are planning to fly a balloon to the Moon. OK, to be more precise, what they’re planning is the use of a stratospheric balloon as a launch platform for their attempt to win Google’s Lunar X Prize. It’s not as crazy as it sounds… the disadvantages of launching from an unstable platform like a balloon may be more than offset by the advantages of launching from an altitude that is above most of the Earth’s atmosphere.
Nov 032009
It looks like the Mythbusters tend to ignore air resistance.
In a recent episode, they claimed to have demonstrated that a horizontally fired bullet and a bullet that is simply dropped fall to the ground in the same amount of time. They were wrong. What they actually demonstrated is that air resistance causes the fired bullet to hit the ground more slowly.
Their argument would apply perfectly in a vacuum, as on the surface of the Moon, but not here on the Earth, where the bullet’s motion is governed not just by the laws of gravity, but also by the laws of a non-conservative force, namely air resistance. (Why is it non-conservative? Some of the bullet’s kinetic energy is converted into heat, as it travels through the air at high speed. Unless we also include the thermodynamics of the air into our equations of motion, the equations will not conserve energy, as the amount of kinetic energy converted into heat will just appear “lost”.)
The bullet’s velocity, v, can be written as v2 = vh2 + vv2, where vh is the horizontal and vv is the vertical component. The initial horizontal velocity is v0. The initial vertical velocity is 0.
Air resistance is proportional to the square of the bullet’s velocity. To be precise, acceleration due to air resistance will be
aair = κv2,
where κ is an unknown proportionality factor. (To be more precise, κ = ½cAρm, where c is the dimensionless drag coefficient, A is the bullet’s cross-sectional area, ρ is the density of the air, and m is the bullet’s mass.) The direction of the acceleration will be opposite the direction of the bullet’s motion.
The total acceleration of the bullet will have two components: a vertical component g due to gravity, and a component aair opposite the direction of the bullet’s motion.
The resulting equations of motion can be written as:
dvh/dt = –κvvh,
dvv/dt = g – κvvv.
Right here we can see the culprit: air resistance not only slows the bullet down horizontally, it also reduces its downward acceleration.
This is a simple system of two differential equations in the two unknown functions vh(t) and vv(t). Its solution is not that simple, unfortunately. However, it can be greatly simplified if we notice that given that vv << vh, v ≅ vh, and therefore, we get
dvh/dt = –κvh2,
dvv/dt = g – κvvvh.
This system is solved by
vh = 1/(κt + C1),
vv = vh[(½κt2 + C1t)g + C2].
Given
v0 = 1/(κt0 + C1)
we have
C1 = 1/(v0 – κt0),
which leads to
vh = v0/[κ(t – t0)v0 + 1],
or, if we set t0 = 0,
vh = v0/(κtv0 + 1),
Similarly, given vv(0) = 0, we get C2 = 0, thus
vv = gt(κv0t + 2)/(2κv0t + 2).
The distance traveled horizontally (sh) and vertically (sv) between t0 = 0 and t1 can be obtained by simple integration of the respective velocities with respect to t between 0 and t1:
sh = log(κv0t1 + 1)κ,
sv = g[κv0t1(κv0t1 + 2) – 2log(κv0t1 + 1)]/(2κv0)2.
The claim by the Mythbusters was that the time it took for the fired bullet to hit the ground was only ~40 ms more than the time it took for a dropped bullet to fall, which is a negligible difference. But it is not! Taking g ≅ 10 m/s2, it is easy to see that the time it takes for a bullet to fall from a height of 1 m, using the well-known formula ½gt2, is 447 ms; the difference measured by the Mythbusters is nearly 10% of this number!
Not only did the fired bullet take longer to hit the ground, the Myhtbusters’ exquisite setup allows us to calculate the bullet’s initial velocity v0 and drag coefficient κ. This is possible because the Mythbusters conveniently provided three pieces of information (I am using approximate numbers here): the length of the path that the bullet traveled sh ≅ 100 m), the height of the bullet at the time of firing (sv ≅ 1 m), and the time it took for the fired bullet to hit the ground. Actually, what they provided was the difference between the time for a fired vs. a dropped bullet to hit the ground, but we know what it is for the dropped bullet (and because it is never moving very rapidly, we can ignore air resistance in its case), so t1 = 447 + 40 = 487 ms. The solution is given by
κ = 0.0054 m–1,
v0 = 272.3 m/s.
Given a bullet cross-sectional area of A = 2 cm2 = 2 × 10–4 m2, an approximate air density of ρ = 1 kg/m3, and a bullet mass of m = 20 g = 0.02 kg, the dimensionless drag coefficient for the bullet can be calculated as c = 2κmAρ = 1.08, which is not at all unreasonable for a tumbling bullet. Of course the actual values of A and m may differ from the ones I’m using here, resulting in a different value for the dimensionless drag coefficient c.
Oct 282009
It appears that the test launch of NASA’s Ares I-X rocket was successful. This is very good news indeed.
Oct 152009
First, it was the multiverse. Then came Boltzmann brains. Now here’s another intriguing idea: the cancellation of the Superconducting Supercollider project in the 1990s and last year’s failure of one of the Large Hadron Collider’s magnets at CERN are just two manifestations of manifest bad luck brought about by the fact that the Higgs particle simply cannot be discovered; that its discovery at any time in the future propagates backwards in time, causing events that prevent its discovery in the first place.
An intriguing idea, though not precisely original, as something much like it was already published in the form of John Cramer‘s excellent science fiction novel, Einstein’s Bridge. And when I say intriguing, I mean intriguing… as the basis of a science fiction story. But as the basis of a scientific paper? Another adjective comes to my mind… appalling.
Sep 242009
There are certain areas of life where decades of computer expertise are quite useless, and even a reasonably thorough knowledge of theoretical physics is only of marginal use. Replacing the rotted subfloor around a leaky toilet is one such area.
Yet this is what I am presently engaged in. So far so good… using some rather evil, foul-sounding power tools, I managed to cut out much of a square hole around the drainpipe, I’m only having trouble with some corners where the power tools don’t reach. Unfortunately, I found out that the subfloor in this bathroom is actually an inch thick, as opposed to the standard, 5/8″ board that I already bought… oh well, it wasn’t a big expense anyway, and perhaps I can use that board for some other purpose later on.
For now, it’s back to Home Depot to get a piece of inch-thick wood and also some advice on cutting out those nasty corners. Maybe they can suggest a method that would be slightly more efficient than the hammer-and-chisel approach which I attempted, with some limited success.
While I’m at it, I shall also inquire as to whether it is possible for them to cut my boards to shape to fit around the drainpipe, so that I wouldn’t have to attempt such precision cutting using my fairly limited skills and perhaps less-than-adequate set of tools. Not to mention that I value my fingers, and prefer to have all ten of them in the right place and in full working order after I’m done with all this…
But for now, it’s rest time. I have this nasty tensor algebra program to tackle, but no matter how difficult it is, I sweat a lot less doing it than when I’m cutting a subfloor with a circular saw.
Sep 022009
If you’re a scientist or engineer, you don’t need to be a pacifist never to work for the military. J. Reece Roth, a 72-year old professor emeritus at the University of Tennessee, didn’t know this when he hired two graduate students (one from Iran, one from China) and when he took his laptop to China. His reward, for a lifetime of working hard and being a loyal citizen of the United States? Four years in prison.
Aug 252009
I’m reading the autobiography of Fred Hoyle, and I’ve been perusing Wikipedia for background, in particular, reading about the Jodrell Bank radio telescope and its founder, Sir Bernard Lovell.
This is how I came across a news item from earlier this year, according to which Lovell recently revealed that back in 1963, he has been targeted by Soviet assassins during a visit to the Soviet Union.
This sounds improbable except… even in recent years, Russian intelligence agents/agencies have been using novel methods in assassination attempts (e.g., radioactive polonium in the case of Litvinenko). Further, the rationale Lovell gives is quite plausible: back in 1963, when satellite-based early warning systems were not yet available, something like Jodrell Bank may very well have served either as an over-the-horizon radar or perhaps using the Moon as a reflector.
Lovell promises to reveal more posthumously. What can I say? Our curiosity can wait. I wish him many more happy and healthy years.
Aug 152009
I’m watching Cubers on the CBC, a documentary about the revival of interest in Rubik’s Cube, and a recent Rubik’s Cube solvers’ competition. What can I say… it takes me back.
I wouldn’t stand a chance competing in this crowd, but I did win the world’s first (as far as I know) Rubik’s Cube competition, held in Budapest in 1980. I completed my cube in 55 seconds, which wasn’t a very good time by my standards then (I often managed to solve the cube in well under 30 seconds) but it was enough to win.
These days, world class competitors solve the cube in 15 seconds or less. In addition to manual dexterity, such spectacular performances also require memorizing a large number of moves. And then I am not even going to mention the blindfold competitions, involving not just the “standard” 3×3×3 cube but the larger, 4×4×4 and 5×5×5 versions… such skills are hard to comprehend.
I can still solve my (3×3×3) cube without trouble (so long as I am allowed to use my eyes), but I only remember a relatively modest number of moves, which means that my solution is far from efficient. In other words… I am rusty. And my cube is sticky. Literally, it feels sticky on the outside (is the plastic decomposing?) and it’s a bit hard to turn. Still, on the third try, I managed to solve it in a minute an 45 seconds. Not bad, considering that I haven’t touched the thing in years.
Aug 012009
Canadian astronaut Julie Payette is safely back on terra firma. During the post-mission press conference, she described the environment in which the International Space Station has been constructed, i.e., space, as “one of the most hostile”.
But… is it?
The funny thing is, while the human body is not designed to survive in space, if you suddenly found yourself floating outside the ISS, you’d have several seconds of useful consciousness before passing out. Further, if you managed to get back in before too many seconds have passed, you might survive the experience with only minor wear and tear and no permanent damage. (Yes, that infamous scene in 2001: A Space Odyssey is scientifically plausible.)
Compare this to the bottom of the ocean. How long would you survive under a pressure of several hundred atmospheres? Or consider the crater of an active volcano. How many seconds of consciousness would you enjoy before your body is vaporized?
And then I have not even considered something like the surface of the Sun (not to mention its interior.) Talk about hostile!
The thing is, space is hostile alright, but we are creatures of the near vacuum: we can briefly survive in vacuum, even return from it without major injury. Even for our machines, it’s much easier to survive in space than it is to survive elsewhere. Perhaps this should be seen as encouraging… once we master the challenge of getting out of the Earth’s gravity well economically, living in space may not be as hard as it sounds.