A Memorial for my Refrigerator

When she was born, I was a boy.  I walked three blocks to my neighborhood school every day to attend the sixth grade.  My teacher's name was Ms. Skaros.  The Rubik's Cube had just been invented, and the hot new teen fashion style was "preppy."  My voice hadn't broken yet.  My "girlfriend" was Anne Schultz.
"The Wall" was still hugely popular, although "That Wall" had not yet been torn down.   The military action of the day in Afghanistan involved the U.S.S.R., not the United States.  Rambo had just tasted his First Blood.  The Officer was just becoming a Gentleman.
James Rockford could have put his $0.79/lb steak in this refrigerator.  The Muppet Show could have had one of these refrigerators in their green room.  The Talking Heads hadn't started making Stop Making Sense yet.
A handful of computers existed on the "Internet," although the web was still a decade to come.  The hot new computers were from IBM and the software was from Wordstar.  Microsoft Word hadn't been invented.  Pac Man was the video game craze.  Apple's new Lisa computers were a flop.
The big Packer's "B" was Bart, not Brett.  The Milwaukee Brewers took their only trip to the World Series.
Pioneer 11 had encountered Saturn three years before, paving the way for Voyager 2's first real close-up and color pictures of this ringed planet and its moons.  The controversy over how fast our universe was flying apart was starting to rage.
This is the world my refrigerator was born to in the year 1982.  Someone else purchased this refrigerator then to keep their vittles cold, and I inherited it.  Now it is time to move on to a more efficient and useful one.  May she rest in pieces at the landfill.

Parallel Theories

I happened to see "Parallel Universes," one of those History Channel shows where they bring together a bunch of astronomers and glitzy graphics to expound on some exotic topic. In this case, the topic of parallel universes. As usual, they pull out stacks of stock animations for fill, and interview real life astronomers to enhance the credibility of the show. Most of the water is carried by Michio Kaku, Max Tegmark, and History Channel mainstay Alex Filippenko. There are parts of the show which are quite interesting, and I grant that the show's producers have done a workman-like job of explaining very difficult topics.

Along the way they give a lesson on string theory of all things. More amazing to me is that they basically claim that string theory is accepted and is a wonderful description of the universe. Back in reality-ville, I can't think of an prediction by string theory that has been verified by observation. Strike that, I'm not aware of a single clear observational prediction made by string theory PERIOD! For that matter, many of the theories of the parallel universes described by the program ("level 1", "level 2", and so on) are described with such absolute certainty that the viewer might be fooled into believing that we already know they exist. We don't. The entire show is really on the borderline with fantasy science fiction.

These kinds of shows are cute, and at some level they build awareness of science in the general public, which is a good thing. On the other hand, their focus on the exotic and extreme topics is disappointing. Our universe is wonderful and beautiful enough by itself that it doesn't need to photoshopped and video toasted to death.

By taking marginal theories and pretending they are mainstream, History Channel is not really doing the public a service. And the professional astronomers who offer sound bites come out looking a little kooky. I wonder if they knew how much their interviews were going to be edited they would have done the show in the first place. There are several places where comical visual effects are used to make them look somewhat like buffoons.

(Except perhaps for Max Tegmark who comes off looking very serious but a little sickly.)

Putting snarkiness aside, I have this request:
Dear History Channel, overall the quality of your "Universe" shows is very high. Keep it that way by sticking to facts, and at the very least, noting where the show dips into speculative territory. Thanks.
(image credits: History Channel, excerpted for the purposes of commentary)

Pioneering Misinformation

Slashdot is running a story about a physics experiment to be performed with the Rosetta spacecraft,

...but the slingshot itself will allow ESA scientists to examine the trajectory for unusual changes seen in several other probes' velocities. An unaccountable variation was first noticed as excess speed in Pioneers 11 and 12, and has since been called the Pioneer Anomaly.

Uh, no, sorry, that would be Pioneer 10 and 11, not 11 and 12. I should know, I've done a little work on the subject.

The so-called flyby anomaly that would be measured with Rosetta is quite distinct from the "Pioneer Anomaly." Both are unexplained discrepancies between measured Doppler shift data and currently understood theory, but the Pioneer Anomaly pertains to unexplained gradual velocity shifts of spacecraft cruising through deep space, while flyby anomalies pertain to sudden impulses as a spacecraft swings by the earth. Both discrepancies have been observed. In all likelihood, these experiments are telling us that our models of the classical physical forces affecting these spacecraft are not complete. Perhaps, on the odd chance that there is "new physics" involved, both anomalies are related somehow. But they definitely not the same observed effect.

Thankfully the original ESA press release gets these points correct. The more subtle points seem to have gotten lost in translation on the way to publication in Slashdot.

Noctilucent Emissions

There's a new study suggesting that "noctilucent clouds" are caused by the plumes of space shuttle launches, which is somewhat ironic for me. For those that don't know, noctilucent clouds are the highest clouds found in the Earth's atmosphere. They are ice crystals floating high in the mesosphere, where large amounts of moisture are not typically found, and are usually only seen in twilight when the setting sun illuminates them against the dark sky. There is also evidence that these clouds are a modern phenomenon, within the past century, and so they may be related to human activity, or perhaps climate change.

Noctilucent clouds over Lake Saimaa. Photograph taken by Mika Yrjölä. Permission by Creative Commons Attribution 2.0 License (from Wikipedia).

Early studies have suggested that noctilucent clouds were caused by space shuttle launches. The space shuttle exhaust plume is composed mostly of water vapor. As the shuttle launches into orbit, it can dump significant amounts of water vapor into the upper atmosphere as it passes through it. More recent studies by Dr. Michael Kelley have added credence to that idea: shuttle launches in 2003 and 2007 produced corresponding noctilucent clouds.

NASA launched a satellite called AIM in 2007 to study noctilucent clouds. AIM stands for Aeronomy of Ice in the Mesosphere. AIM continues to study the phenomenon using several instruments, including two imagers and a meteoric dust measuring device.

The part I find ironic is that NASA launched a satellite to study a phenomenon caused... by the launch of NASA satellites!

OK, there are far more noctilucent clouds than can be entirely explained by shuttle launches, so this is not a complete exercise in navel-gazing. The shuttle-noctilucent connection was known before AIM was selected by NASA.

Update 2009-07-30: Added noctilucent cloud image from Wikipedia.

Solar Dud or Doozy?

There is some news in the past few days that the a few new sunspots are appearing, it may be that the next period of solar activity has begun. Will it be a dud or a doozy?

The sun has a quite regular cycle that repeats about every 11.5 years. Each cycle represents a reversal of the the sun's magnetic field -- magnetic north becomes south, south becomes north -- so it actually takes 23 years for the sun's magnetic field structure to return to its starting configuration.

During one of these 11.5 year cycles, the sun's magnetic field gets tangled and wound up in its circulating convective zone, located in the outer third of the sun. Once in a while, the magnetic field pokes out from the beneath the surface, and a sunspot appears. So sunspots are indicators of the how chaotic the magnetic field is within the sun.

Solar activity is a problem for us on the earth since the energetic particles ejected during solar storms can affect communications, power grids and the orbits of satellites. Being able to predict the the solar cycle, both timing and strength, is a valuable tool that can save lives and equipment. Unfortunately, predictions have been more of an art than a science.

I was really intrigued by a presentation at the 2005 AAS conference several years ago by Peter Gilman and Mausumi Dikpati, which claimed an improved method for solar cycle prediction. Their solar model showed that the solar convective zone had large scale circulations, almost like oceanic currents on earth. They also showed that it takes approximately three solar cycles for the solar flows -- which are almost like conveyor belts -- to make one circuit. Thus, they could train a reasonably accurate predictive model, based on the known solar activity from three cycles before (with the added benefit, that it produces predictions for about three cycles into the future as well). Their prediction was that the current solar maximum would be delayed by 6-12 months, but 30-50% more intense than the previous cycle. The "conventional" predictions were calling for the beginning of the cycle to begin in early 2007, while Dikpati and Gilman's group were calling for activity starting in the late 2007 to 2008 time frame.

Well at this stage, it's clear that both the conventional and new Dikpati/Gilman predictions were wrong, since we're past halfway into 2009 before any serious solar activity has appeared. But it's interesting that the onset of the cycle has indeed been delayed from its expected appearance, which indicates that perhaps there is something behind the Dikpati/Gilman model. The "conventional" prediction was recently revised, and now claims that the next cycle will be a dud -- weaker than usual. I've had a little harder time determining if the Dikpati/Gilman group has revised their forecast for the strength of the cycle.

Either way, I think it will be an interesting cycle to watch. I actually hope this solar cycle is an extreme -- either a dud or a doozy -- rather than an average one. Extremes are much better test cases for theories than boring average cases. While I have something to lose if this cycle is a strong one, at least it would be lost in advancement of science.

Multiplier Effect

Because of the developing economic crisis, I've been reading more economics blogs. My favorites are Econbrowser, hosted by Profs. Hamilton and Chinn; Macro-Man an anonymous but extremely incisive and hilarious day-trader^*; and Follow the Money by Brad Setser. Any other reader favorites?

One excellent post by Prof. Chinn has direct relevance to governmental policy initiatives to deal with the economic problems. Her post is based on work by Mark Zandi of Economy.com. The question is: given that the economy needs to be stimulated, what method of stimulation yields the largest economic benefit. The benefit here is expressed as the stimulus multiplier, which is the amount of increase in GDP per unit of stimulus. For example, if we simply gave every person in the country $1, each could go out and buy a McDonald's value menu item. But the benefit doesn't stop there because with the increased consumption, McDonald's has to hire more workers, who in turn consume more; purchase more supplies from its suppliers, who in turn hire more workers, etc. So in principle, a $1 stimulus package can have more than $1 benefit to overall production.

So which economic stimuli had the greatest benefit? The top three were:

• Temporarily Increase Food-stamps (multiplier 1.73)
• Extend Unemployment Insurance Benefits (multiplier 1.64)
• Increase Infrastructure Spending (multiplier 1.59)

The first two items have the obvious benefits of keeping people on their feet, but also provide an extra 64-73% advantage beyond the direct stimulus. Of course these benefits can only be temporary. On the other hand, the third item has the advantage of improving neglected infrastructure -- a long term "capital gain" -- while at the same time providing an extra 60% bang for our buck.

Now for the worst stimulus concepts:

• Make Bush Tax Cuts Permanent (multiplier 0.29)
• Cut Corporate Tax Rate (multiplier 0.30)
• Make Dividend Tax Cuts Permanent (multiplier 0.37)

Since these multipliers are less than unity, it means that for every dollar of tax break, the country's production actually goes down. Of course some small segment of the population may benefit from such tax cuts, but in hard economic times, it's not clear why they would deserve a benefit when the broad population and the overall economy do not. To be fair, a few of the tax cut concepts do a little bit better, most most are break-even at best.

Note that these tax cuts that are discussed most readily as the solution to the economic problems have some of the worst possible effects on the economy. In fact, a tax cut actually hinders production, compared to other stimuli. Dr. Chinn discusses some reasons this may be true.

What fascinates me is the question of whether the multipliers work in reverse. If reducing corporate taxes by $1.00 hobbles the economy by $0.70, then would raising taxes by $1.00 improve the economy by $0.30? As heretical as that sounds, it seems that while raising taxes will withdraw $1.00 from corporate coffers and hence from the economy, it enables the government to spend $1.00 on more needful and worthy areas (say, on stimuli that have a large multiplier!).

The situation is somewhat more complicated because each of the stimulus concepts have different time scales, so it would require a more delicate touch than brute force. But it would be nice if, in the political dialog about what to do next, actual economic data would be used rather than mindless rhetoric with zero substantiation.

Unstable Physical World

A very interesting paper just appeared on the arxiv.org preprint server. It presents the work of two different groups measuring the radiactive decay rates of two specific isotopes, Silicon-32 and Radium-226, who found some strange and intriguing results indeed.

Scientists believe we live in a universe where physical "laws" apply the same everywhere. It shouldn't matter whether we are on the earth, the moon, or the depths of outer space, the equations and theories should be the same. Radioactive decay is governed by the so-called "weak force," which is in principle a nuclear-scale force that shouldn't really care about the anything beyond the nucleus itself. So it is natural to expect that Silicon and Radium should decay radioactively at the same rate wherever we find it.

But that's not what was found by Jenkins et al. in their analysis. Taking data from two different laboratories, at Brookhaven National Laboratories in New York State and another in Germany, the authors found the decay rate goes up and down with an annual cycle. See this blog entry for a graph. The variations are less than a tenth of a percent over the course of a year for both radioisotopes.

The authors speculate that the effect is dependent on the distance between the sun and earth, which also has an annual periodic modulation as the earth moves in its orbit between perihelion and aphelion. Of course, this would violate our precepts about the physical laws governing radioactive decay. They further speculate that this may be due to a changes in the amount of solar neutrinos that reach the earth, which might somehow modulate the nuclear decay rates. Or, perhaps it is a variation in the "fine structure constant" with distance from the sun (the fine structure constant dictates the strength of the weak force).

However, if you look closely at the graph, you will see that the radioactive decay rates and the distance variations do not match up quite that well. In fact, the measurements lag the distance template by a few months. I can't imagine what force law could describe such an oddity, but it is definitely not a simple distance relationship.

An experimenter needs to be worried about subtle biases. Both of the experiments were done in the northern hemisphere. Perhaps there is some kind of earth-bound seasonal effect? For example, there could be seasonal temperature variations that affect the sensors. Or, it could be something even more subtle, like annual changes in the cosmic ray flux which affect detector dead-time. An interesting test would be to use a southern hemisphere lab where any seasonal biases would be reversed. There have been some other spectacular results which have been later retracted due to failure to account for equipment (mal)function. A famous example of this was the discovery of a 2000 Hz optical pulsar in Supernova 1987a, which later turned out to be electrical interference from another piece of equipment. These people are not dumb, it's just that the physical world can be more complicated than the ways we can control.

It's worth noting that this paper has apparently not yet been refereed. It's quite possible that during the refereeing process, a lot of these points will be addressed, or the conclusions of the paper might change. Until then, it's still a quite fascinating result!