While looking for a good online Pb isotope evolution curve, I stumbled across the Planetary Science Research Discoveries site. It is an archive of popular science explanations of research papers in the planetary science and cosmochemistry field.
I've read a bunch of these articles, and they are brilliant. This is great, because I've been wanting to summarize some of these topics, but now I have found that people much more eloquent that I have already done so. All I need to do is link them.
So, here are some lovely writeup on:
Dating the earliest solar system condensates
Galactic migration and presolar grains
Gas giant migration hypothesis for the late heavy bombardment
I'm happy to field questions about any of these, although my ability to answer questions about orbital modelling is fairly limited.
Disclaimer: Geoff Taylor has collaborated with the scientists I work for and has visited our lab. None of these articles relate to that research.
Sunday, April 29, 2007
While looking for a good online Pb isotope evolution curve, I stumbled across the Planetary Science Research Discoveries site. It is an archive of popular science explanations of research papers in the planetary science and cosmochemistry field.
Friday, April 27, 2007
Disclaimer- this was the post I was working on before Mrs. Lemming went into labor. I apologize for any change of tone halfway through. But seeing how she was attacked by lawyers this week, I’m gonna dedicate this post to the writer of Retrospectacle. Ms. Shelley Batts, this parrot’s for you.
The American sweetgum (liquidambar styraciflua) is a deciduous coastal plain tree that grows from around New York City down the Atlantic seaboard well into the Deep South. It is notorious for its sweet gum balls, which are spiky, hard, inch-sized fruit which are painful underfoot and remarkably resistant to rot, predation, conflagration, or any other means of destruction. We had a big sweet gum tree in the house where I grew up, and after raking them into the compost heap, we could find layers where they would remain years after everything else rotted away. If not raked up, they would inevitably get frozen into the dog’s fur in winter, or get picked up by the lawnmower and accelerated (undamaged, of course), into my shins. It was a family joke that they were so indestructible that after the sun burned out and blasted the Earth’s atmosphere and biota to a crisp, the sweetgum balls would remain, the only biological object refactory enough to survive the inferno and bear testament to the former presence of life on the planet.
Of course, that was an American view of the balls. Here in Australia, they are considered bird candy.
Liquidambar (as they are locally known, to differentiate them from eucalypt “gum” trees) are a relatively common decorative tree planted in Victoria, southern NSW, and here in Canberra. And as this picture above shows (taken by me, with my own camera, not borrowed from any journal via the fair use provision), gang gangs love to eat sweet gum balls.
Unlike sulphur crested cockatoos or galahs, gang gangs are not well adapted to agriculture. They don’t flock to developed areas, and they avoid human contact. Unlike most parrots, I’ve never seen them eat any nuts, birdfood, or fruit. But every autumn, as the foreign deciduous leaves fall and reveal the sweetgum balls, gang gangs fly in from the surrounding native forests to feast on the most indestructible seed pod North American trees have to offer.
Wednesday, April 25, 2007
The European Southern Observatory has released a press release claiming to have found a possible terrestrial planet in the habitable zone around the red dwarf Gliese 581.
Rampant speculation has ensued.
I’ll give the facts as I see them, but since I’m not an astronomer I may need to be corrected.
The radial acceleration method measures the pull exerted on the host star by an orbiting planet. These measurements can be done extremely precisely. Since they rely on the law of gravitation, they can detect smaller masses if you have a small star and a close planet.
The wobble that is detected gives the orbital period (which, given the mass of the star, yields the orbital distance), and the amplitude, which is dependent on the mass of the planet and the geometric configuration.
The reported mass is a minimum mass- that is, it is the mass if, from the exoplanet’s POV, our sun lies in the plane of that exoplanet’s ecliptic. Otherwise, the actual mass is greater than this minimum mass by 1/cos X, where X is the angle between our sun and their ecliptic. Fancy spherical geometry* thus suggests that the actual mass is unlikely to be more than 30% higher than the minimum mass.
So this new exoplanet probably has an actual mass between 5.5 and 7 or so Earth masses.
The mass, and the orbital period are all we can actually determine at this point in time.
There have been reports of a planetary radius. As far as I can tell, these assume a terrestrial (or icy) composition, with a little bit of gravitational self-compression thrown in.
Obviously, such assumptions are speculative- the terrestrial planets in our own system don’t even have the same bulk composition as each other. Neither do the icy moons.
The presence or absence of water is also speculative. It is worth noting, however, that on Earth, most of the water is believed to have been added late in planetary formation. The late veneer hypothesis suggests that volatiles and highly siderophile elements were added to the Earth late in its formation from impacts of outer solar system objects. While our solar system has several gas giants to gravitationally deflect bodies inwards, no such giant planets exist in the Gliese 581 system outward of planet c (planet b is only 8 earth masses- compared to 318 earth masses for Jupiter).
Additionally, spectroscopic attempts to identify water in other exoplanet- the hot jupiters HD 209458 and HD 189733- failed to identify water in the atmosphere of either planet. This is despite theorists claiming that it had to be there.
Of course, an unusual result shouldn’t be surprising. Ever since we went to the moon, the rule of thumb for planetary exploration is that they have been stranger than anything we could hypothesize. So my guess is that Gliese 581c will adhere to this rule.
At the moment, all we can do is guess about this planet’s composition. But hopefully, the Terrestrial Planet Finder (recently bloged at green gabbro), if funded, will be able to image it, and determine the IR spectra. The key fact about this new discovery is that if the TPF gets flown, it now has one definite target to analyze. And since the signal for this planet was 3 times the LOD, hopefully more will follow.
Of course, if there is anyone living there, and they look out towards the galactic rim, this is what they will see:
Orion is to the left, the Pleadies are to the right, and somewhere in this picture is our sun. Can you find it?
* I've only estimated this, feel free to quantitatively set me straight.
Saturday, April 21, 2007
I am currently on a two week unpaid sabbatical known as “paternity leave”. The purpose of this break is to keep Mrs. Lemming sane and happy, and one of the major components is addressing the nappy question.
Above are the various options available. There is the basic cloth nappy, the disposable nappy, and the hi-tech eco-yuppy excrement management system that got sent to us from the US. It is my job to experimentally determine the best use for all of our shit-stopping assets before I go back to work. If anyone’s interested, I can do a more extensive description of the bonuses or deficiencies of each, possibly including some semi-quantitative data. Or, I can get cracking on the lead isotopic evolution post. Any requests?
I admire Sciencewoman’s ability as a scientist, her honest in blogging, and her generosity in sharing her work / motherhood juggle under difficult circumstances. However, I suspect that we disagree on politics. She recently posted pictures of baby clothes in support of the pro-censorship group Momsrising, whose philosophy seems to include teaching their daughters that the correct response to having their feelings hurt is to get the offender fired.
In the interest of expressing diverse political viewpoints between science bloggers, here is my response.
Note that I used computer effects, since I can’t afford to politicize my daughter’s entire wardrobe.
Friday, April 20, 2007
Sean has a nice post at cosmic variance on the difference between science and math.
Thermochronic has talked a bit more about the politics of reviews. I have news as well. Last Monday, I was asked to review a paper. On Tuesday, I got the paper. On Wednesday, Mrs. Lemming went into labor, and I haven’t glanced at anything but the “please complete by” date since.
So I don’t really know what I am going to say yet, but I think I’ll sign it. One the one hand, I don’t like advocating actions I’m not willing to take. Also, as a technician, I don’t live and die by the whims of publishing. I’m actually paid to keep machines running and samples processed. If I end up on the blacklist of an infamous Topeka ubergeologist, it doesn’t really effect my job performance.
Mostly, though, my experience in science is that I’ve never gotten anywhere simply by not stuffing up. All of my jobs, degree acceptances, etc. have come from taking a gamble and pulling something just a little bit crazy off. I’ve never gotten anywhere via the normal channels. So at this point in my career, rattling cages, taking risks, and stirring pots is second nature to me.
Sciencewoman is the amazing researcher/ mother. See her posts on taking a baby to the field and seminars.
I just finished my contribution to a paper during the little one's nap. This is the data reduction/writeup that I was going to do last Wednesday evening.
Chronology of evil media empires: does anyone know how many hours passed between NBC firing Imus and then airing the psychopath tapes? We don’t get that much American news over here, and I’ve been preoccupied. But I'm disgusted enough to trade any NBC shares I might own in for part of some tobacco company.
There were a couple of other really good science blog posts last week while we were in hospital, but I can’t remember where. Any tips/ suggestions?
Thursday, April 19, 2007
Consider this my Frink Tank tribute:
For those who don’t get it:
If you don’t know what vegemite is, hang out with more Australians; it is a cultural subtlety not learnable from a book.
If you don’t know what meconium is, look it up on the web.
If you don’t know what the white soiled bit of fabric is, you need to spend less time in disposable, consumerist culture.
If you understand all of this, but still aren’t amused, that just means that you have taste. If that is the case, stay away from vegemite.
Take a close look at the print on her jumpsuit. And that, my friends, is about as close as we are going to get to geology this week. I hope to post on the lead isotopic evolution of the Earth soon- it is timely, as lead isotopes are used for studying pregnancy and lactation.
But I need to review a paper and write my section of another and prepare a talk for next month. And then there’s the nappies and bellytime and snuggles.
LLLL is one week old today.
Tuesday, April 17, 2007
I’ll try to keep this short, since I should really be sleeping, but I just wanted to mention that my heart goes out to the victims and the families of all the people wounded or killed in Blacksburg yesterday. I haven’t read what the rest of the blogosphere has said on this matter. Even before I was a dad I didn’t have time for political blogs, and people who spin tragedies for their own agendas piss me off. But I will say this:
There has been some questioning, at least in the Australian media, about the the shooter. In many of these cases, there is a lot of interest in the criminal- his motives, his upbringing, his personality. The media, and possibly the public, seems to have a lot of questions about these sorts of people.
These questions do not have interesting answers.
The short answer is that the people who commit murder are losers. People with emotional maturity and deep character- interesting people- adapt and survive instead of killing people. A few years ago, I was talking to a friend of mine who is a professor of criminal law, and who researches murder cases for a living. He pointed out that in most of the cases he studied, the victims were more interesting than the perpetrators. But you don’t need to talk to professors to know this; a bestselling Australian author has reached the same conclusion.
Joe Cinque was the victim of the Australian National University’s most famous murder case. Back in the drug-addled good-old-days of the mid 90’s, a few bright, young, anti-conservative law students had a party where they discussed whether or not they were good enough at their chosen field to beat a murder rap. Two of these students proceeded to test the hypothetical, by drugging then poisoning one of their boyfriends.
Both students beat the murder charge; the girlfriend of the victim got manslaughter, and her accomplice walked out of court a free woman. Author Helen Garner spent 5 years researching the case and writing the book. In the process, she found that even though the murderers were some of the most ambitious, intelligent young minds the country had to offer, their emotional immaturity and selfishness actually made them far less interesting than the victim, Mr. Cinque. The book is Joe Cinque’s Consolation, and is available here.
So if the TV talking heads and radio chatbackers are incessantly speculating about the Va Tech murderer, simply turn it off and read Ms. Garner’s book. By the time you finish it, some of the bereaved from this latest tragedy may be wanting to share their stories, and the stories of the victims will almost certainly be more interesting and moving than those of the assailant.
Friday, April 13, 2007
The universe contains something on the order of 10,000,000,000,000,000,0,00,000 stars. Around these stars orbit an mind-boggling number of planets, moons, dwarf planets, and other heavenly bodies. They must host innumerable life forms, exotic features. These surely include biomes and civilizations that dwarf our understanding and imagination. But in all that vast expanse of space, time, and complexity, there is nothing beautiful enough to hold a candle (standard or otherwise) to my daughter.
Little Lovely Lab Lemming was born so recently that her light cone has yet to reach Voyager 1. But when the rest of existence can detect her utter cuteness, I’m sure they’ll be as smitten as I am.
Life is beautiful.
Monday, April 09, 2007
Karri trees are the tallest species of Eucalypt native to Western Australia. As a valuable, fast-growing timber resource, they have been logged since at least the end of the 19th century. Despite growing in the wetter, cooler, more temperate regions of the state, Karri forests are fire prone. Prior to the invention of the airplane, fire spotting in Karri country was tricky. Since the trees can be more than 80 meters (250 feet) tall, you need a pretty big tower to see over them. Unless you build a treefort.
In the early 20th century, almost a dozen fire towers were built in the tops of high standing karri trees for fire spotting. Two of these towers still exist, and are open to the public. One of them is still functional. In addition, during the bicentennial (1988), a replica tree tower was built in Warren National Park. At 74 meters, this is not only the highest tree tower, it is the tallest fire tower of any kind (if Wikipedia can be trusted) currently standing. From the top, you can see lots of other really tall trees, and the roof of the visitor’s center far below.
Unlike the original towers, this new tree has a rest platform a third of the way up. This gave me a steady location from which to photograph the patient and lovely Mrs. Lemming, who scampered down in a fraction of the time of her acrophobic husband.
Tip for would-be tree climbers: Don’t wear sandals. Any slight nervousness can combine with warm summer temperatures to cause the soles of the feet to sweat. This reduces the coefficient of friction on the foot/sandal interface, reducing stability and increasing the anxiety that generates this perspiration. I think climate guys call that positive feedback. I just found it to be unnerving.
Sunday, April 08, 2007
Friday, April 06, 2007
A while back AmI, Dr. Shellie, James and CJ commented on various problems with the review system, and more recently Yami McMoots had a complaint about reviews of funding applications. All are worth a read. However, I disagree with the suggestion by Yami and AmI (I really need a better handle for her, BTW) that a double blind process would solve some of these problems. I think double blinding would make abusive reviews easier, and a fully attributable review system would be preferable.
The first problem with a double-blind system is that for many geology and planetary applications, the anonymity of the authors is laughably fragile. Suppose, for example, that I were to write a paper using SHRIMP or laser ICPMS results (those are the instruments that consume 90% of my time). Assuming my methods section adequately describes these unique systems, then the anonymous reviewers will be able to determine which research group I am a part of. Combining that with the subject matter and/or field area will give them a pretty good idea of who the authors are likely to be.
For planetary science, the situation is even worse. Suppose a reviewer gets a paper on recent UV spectrometry results from Jupiter. The only UV spectrometer within 500 million km of Jupiter is on the New Horizons spacecraft, and the science team for that mission is posted on the internet. Double blind quickly becomes single blind if the reviewers decide they want to know whose paper they have. At least with a fully attributable system, everybody has the same level of transparency.
Finally, the most common complaint about “bad” reviews is not the amount of criticism. Rather, it is generally the lack of science on which that criticism is based. Most people get over fair but harsh reviews; rather it is the inane, mean-spirited (and always anonymous) reviews that are really frustrating. If reviews were signed, and included in supplementary material archives, then the cost to one’s reputation for writing such reviews would be substantially higher than it would be under a partially or totally blind system.
Of course, it’s easy for pudknockers like
us me to complain about this sort of behavior and suggest theoretical fixes. I have absolutely no power to implement such suggestions. We can swamp Google’s hard drives with quibblings about the best sort of review system, but it won’t mean diddlysquat until a statistically meaningful number of journal editors switch to various systems and compare the results. And they aren’t likely to change.
After all, the powers-that-be have spent considerable time and effort schmoozing in smoke-filled rooms in order to make the connections and handshakes necessary to game the review process. It is only natural for them to want to preserve the advantage bought with Cuban tobacco and intellectual kickbacks. But there is a change that would open the process without making life difficult for the kingpins of the scientific establishment.
Department heads could require tenure applicants to include a collection of signed reviews as part of their tenure portfolio. This would illuminate the applicant’s standing in his or her field of research, and more importantly, it would cost the Haupt-professors nothing- the work and risk would be borne by the associate professors and lecturers. And it would actually make life easier for editors, as many fields are currently suffering from a shortage of willing reviewers. Of course, the follow-on effect would be to decrease the proportion of anonymous reviews, in a way that benefits science as a whole. So everybody wins.
Wednesday, April 04, 2007
Three minutes before sundown, to be exact, while the sun was making all the hilltops pink and pretty.
I read that it was possible under good viewing conditions, and a few weeks ago the Bad Astronomer posted about spotting Venus in the daytime. Canberra is dry and 600 meters high, and this time of year the star is just north of straight up at sundown. So, I went out last week to line it up with a telephone pole. Then I went out progressively earlier each clear day to try and spot it. Sunday I caught it 5 minutes after, and yesterday was brisk and clear high pressure, with just a few high wispy clouds to focus on. I tried half an hour before with no luck, but at 5:52, it was right where it should be, twinkling between the wisps of cloud 8.7 light years below.
I had a brief look for Canopus, which is just a bit south of due up, but it is substantially dimmer, and I haven’t lined any landmarks up. Still, it is cool to confirm that the stars are still there during the day, even if they can't quite shine through the fuzzy blue atmosphere.
Tuesday, April 03, 2007
There was a tsunami warning on the radio this morning. Evidently the Solomon Islands event triggered the regional network, so all the boffin-to-yobbo communication networks sprung into action. Since Canberra is 100 km inland and 600 meters above sea level, I didn't pay it much attention, but evidently the wave height on the coast was 10-20 cm.
Not exactly a city-destroying wave of doom, but better to try the new system on one of these than a M 9.5 monster or a caldera collapse on the Kermedec. The main problem was that in Sydney, all the tourists flocked down to the shoreline to see why all the ferries stopped and the harbor was cleared. Go figure.
I haven't had a chance to find the USGS report, or to look up relief agencies, but a NZ or Australian news search should get you to the latter.
Monday, April 02, 2007
The obesity epidemic in America has reached relativistic proportions, with some overweight citizens gaining so much weight that they distort the space and time around them. As the photo below demonstrates, the largest Americans are now capable of gravitationally lensing their suburban environments.
According to the surgeon general, this represents a disturbing new trend in the fattening up of America. All previous dietary guidelines and predictions have been based on Newtonian physics. Researchers never imagined that people could shovel enough food down their gullets to perturb the space-time continuum. This recent development shows that it is actually possible for human fat cells to gravitationally collapse into degenerate matter.
Naturally, fat groups are outraged. “This is just another facile ploy to blame individuals of stellar mass,” said Julius Gloop, spokesperson for Fat Pride. “We are being victimized by an anomalous law of physics, a law that doesn’t even have the decency to abide by the Standard Model.” Mr. Gloop then struck out at the term “degenerate matter”, claiming that such base and unsubstantiated slurs were not conducive to a healthy debate of American’s eating habits.
“Degenerate to whom? To chemists? To plasma physicists? Obviously this sort of electron shell elitism serves only to denigrate the working poor who can’t afford gym memberships and organic cranberries.” Mr. Gloop then demonstrated that this so-called degeneracy was a boon, as his weight gain actually reduced his pant size, due to the effects of gravitational self-compression. Some physicists found this trend worrying, however.
“There is a practical limit to the amount of weight a person can gain,” said professor Alfred Gauntly of Queanbeyan State University. There comes a point where the carbon and oxygen atoms in fat cells get so close together that they undergo a runaway fusion reaction, producing a spectacular nuclear explosion known to astronomers as a supernova.” The effect of one of these explosions on a typical suburban mall would be rather disruptive. But where some scientists see danger, others see opportunity.
“For years, science has been trying to find a way of rapidly transferring mass in order to measure gravity waves,” countered professor Max Higglebotham of the Nebraskan Oceanography Institute. By compressing some of the relativistically obese into a critical mass, we could create those conditions in the lab, thus testing fundamental theories of gravity.” Indeed, until the widespread adoption of junk food and sedentary living in the western world, scientists did not have the means to grow PhD students who not only blocked out the light, but actually made it bend out of their way. Now these students are in hot demand. “The only problem,” said professor Gauntly, “Is finding ways to maintain their mass during a 6 year PhD program, where all they can afford to eat is Raman noodles.”
Hat tip to cosmic variance for the link to the lensing site.