The Cassini spacecraft shines radio waves towards its large moon Titan on some of the craft’s dozens of close flybys of Titan. The Cassini RADAR experiment measures the reflected radio waves to produce a radio wave picture. Check out this newly released RADAR view of Titan’s fancifully named Xanadu region. Titan may have seeping creeks or rivers and possibly lakes of liquid methane (also known as natural gas - the stuff cow’s produce and that you use to cook spaghetti) in the dark, smooth areas in Xanadu.
Archive for July, 2006
Titan’s Xanadu Seen by Cassini’s Radar
Thursday, July 20th, 2006Slippery Slope Fallacy
Wednesday, July 19th, 2006The Bush administration is invoking the slippery slope argument in its opposition to legislation expanding federal funding of stem cell research. There are numerous sources pointing out that the slippery slope argument is a logical fallacy (just google slippery slope fallacy for a sampling). The slippery slope argument goes like this: if we allow destruction of stem cells for research we will eventually allow vivisection and live human transplants. Or: if we outlaw guns then we will have to outlaw knives. Or: if we legalize gay marriage we’ll have to legalize polygamy. One doesn’t need a degree in logic, philosophy, or law to throw the slippery slope argument out the window.
Here’s one way to see that the slippery slope argument is no argument at all. Every law we have is a matter of degree and would be subject to the slippery slope argument. Here are some examples.
(1) We let people drive 75 mph on the interstate, but this does not oblige us to let them drive 80 mph. Conversely, if you wish, we limit the speed of driving to 75 mph, but this does not force us to limit the speed 70 mph.
(2) Some drugs require prescriptions, some don’t; some are illegal. None of these restrictions puts us on a slippery slope.
(3) We have a federal minimum wage, but it hasn’t changed in almost a decade. Hardly a slippery slope to a higher minimum wage.
(4) We let 16-year-olds drive. Not 15-year-olds.
(5) We lowered the voting age to 18, but no further. No sliding down a slope to toddlers in the voting booth.
(6) You can buy a gun, but not an anti-aircraft weapon. You can carry your gun, but not into a school.
Our entire society is based on drawing lines. The idea that moving the line results in an avalanche down a slippery slope until the line is completely gone is simply absurd. In fact, I cannot think of a single law that does not involve drawing a line across a slippery slope and defining one side as legal and the other as illegal. Legal gay marriage will not oblige legalizing polygamy any more than it will oblige legalizing marriage between people and box turtles. What mythic force pushes anyone down the slippery slope? The U.S. Senate passed the legislation expanding stem cell research funding by a 63-37 vote today (short of the supermajority needed to override Bush’s promised veto). If that were to become law, how exactly would we be forced, or even tempted, to expand it further? If a precedent doesn’t work, we change it. If stem cell research were somehow found to be disastrous, it would be just as easy (even easier, in fact) to reverse this legislation. And Bush did allow limited federal funding of stem cells in 2001 anyway. Why didn’t the slippery slope argument apply then?
Stem Cells and Bush
Tuesday, July 18th, 2006With the U.S. Senate debating legislation to expand federal funding for stem cell research, George W. Bush is threatening his first veto. Bush opposes using “federal taxpayer dollars to support and encourage the destruction of human life for research.” Yet he has spent over $300 billion federal taxpayer dollars to actually destroy human life in Iraq. And if destroying a handful of cells constitutes the destruction of human life, why is he not proposing legislation to criminalize stem cell research and the destruction of unused embryos from in vitro fertilization? Because he is hypocritically pandering to his right-wing base while trying to avoid complete alienation of the vast majority of Americans who favor stem cell research.
Ode to Eccentricity
Monday, July 17th, 2006It seems like scientists have a different meaning for perfectly ordinary words. To an astronomer, for example, “eccentricity” does not mean an inclination to strange behavior. Nor does “inclination” refer to a tendency. There are also the anomalies: true anomaly, mean anomaly, and eccentric anomaly. None of these are anomalous or eccentric. And don’t get me started on wakes. “Eccentricity” is one we deal with all the time. It simply describes how much an object’s orbit differs from a circular orbit. I have noticed an interesting trend among my younger colleagues the last few years: they pronounce “eccentric” either “eh-sentric” or “ee-sentric”. Call me old-fashioned, or maybe eccentric, but I can’t stand by and see a perfectly good double-c get the s-treatment. This ode is dedicated to the eccentrics.
Ode to Eccentricity
by Josh Colwell
“Eccentricity” has two c’s
like “occipital” and “accidentally”.
“Eccentricity” has two c’s
sandwiched between two short e’s.
Syllablically speaking,
If one can do such a thing,
That’s an “ek” then a “cen”:
Two c’s: no redundancy.
To skip one of those c’s
While maybe a breeze
Fills the ears and the brain with a bit of a quease.
Do our cars A-celerate when we step on the gas?
Only acceleration allows us to pass.
Howard Hughes’ bottled pee
Was no sign of E-centricity.
But we don’t need to rely on our O-cipital lobes,
Don’t take it from me,
Check the OED
The word is pronounced “EK-sen-TRISS-ity”
While soft c sounds may be palatable,
“E-centricity” is just not A-ceptable.
Wordplay
Sunday, July 16th, 2006This charming movie looks at the crossword puzzle culture in the United States through the annual American Crossword Puzzle Tournament held at the Marriott hotel in Stamford Connecticut. For someone like me who can spend the better part of a day working on the Sunday New York Times puzzle (not even the toughest one of the week), it was a bit alarming to see people racing through these puzzles in a matter of minutes. The competition itself reminded me of my days playing the Star Trek Customizable Card Game in several ways. The first similarity is the mere existence of such a tournament, though I admit a crossword puzzle tournament is probably less surprising to most people than a Star Trek Customizable Card Game tournament. Second was the impressive dedication of the top contenders to being scarily good at the game (or puzzle solving). A third similarity is the occasional agonizing mistake ruining a top contender’s chances. The charm of the movie is built on the shared passion of a wide variety of people for something as simple but devilishly complicated as a crossword puzzle. Jon Stewart is hilarious as a New York Times crossword puzzle addict. In one scene, we see Stewart, Bill Clinton, and the Indigo Girls working on the same puzzle, and we sense the thrill of the coded connection between the puzzle author and his victims - er, audience.
Zidane Can’t Have it Both Ways
Friday, July 14th, 2006In his first interview with the media since the World Cup final, French soccer hero Zinedine Zidane told Canal Plus that he wanted to apologize to children and those who teach them because “il y a des choses il faut pas faire” (there are things that shouldn’t be done). Presumably his apology was because he didn’t want children to think they should do as he did and physically attack a player who had verbally assaulted him. But when pressed on the question of his own personal regret, he said he did not regret it because “that would mean he (Matarazzi) had the right to say what he said”. Of course, Matarazzi did have the right to say what he said, although maybe it would have been a foul if an official had heard it. Furthermore, not head-butting someone who says something offensive does not mean endorsement of the offensive words. If Zizou really wants children to not do things “il faut pas faire” then he should admit that he shouldn’t have done it. Period. Sadly, it seems that the French media does not want him to regret what he did, because that would place all the responsibility on their national hero and remove it from the Italian trash-talker. The French interviewer portrayed it as a pre-meditated act to restore his family’s honor. To me it looked like someone successfully goaded into losing his temper.
Superman Returns
Friday, July 14th, 2006Bryan Singer brings Superman back to the big screen with a shiny new movie that tips its hat to the Christopher Reeve Superman of the seventies. Brandon Routh’s Clark Kent is uncannily reminiscent of Reeve. “Truth, Justice, and the American Way” has been replaced by “Truth, Justice, all that stuff” - a recognition, perhaps, that these days the “American Way” would be regarded by the rest of the world as starting wars and torturing prisoners. The movie has a number of nice set pieces. The opening airplane disaster is gripping in spite of its absurdity. (But what’s the meaning of the remark that only one network is covering the launch of a new sub-orbital commercial space plane? The comment has no function in the movie, so it must be a commentary on something, but I can’t figure out what.) Kevin Spacey brings a nice mix of humor, evil, and egomania to Lex Luthor. Sadly, the script does not give Lex much intelligence. His evil plan is stupid. Destructive, yes, but it’s hard to imagine how it would do him much good, even if it worked out. This lessens the impact of the final third of the movie.
A Prediction About Saturn’s Rings
Thursday, July 13th, 2006One of the cool things I’ve done with data from Cassini is analyze self-gravity wakes in Saturn’s rings. These are long, finger-likeshaped clumps of particles in the rings (a few tens of meters across and perhaps 100 or more meters long) that are the result of the particles running into each other and trying to accrete through gravity, but getting pulled apart by tides from Saturn. We published a paper earlier this year (Geophysical Research Letters, Vol. 33, L07201, doi:10.1029/2005GL025163 for those interested in the gory details) using our first measurements of Saturn’s A ring to derive the size and shape of the clumps in the ring. I have used that model to predict what we will see with our next measurement on July 25, 2006. You can see the prediction (purple curve) here. The other curves on the plot show the range of values from different measurements to date. Once I get the data I will post a comparison of the observation with the prediction. This is a fun opportunity to see the scientific method in action:
1. Observations by Cassini led to a theorymodel (the theory was proposed more than 30 years ago and has been developed by a number of researchers since then; we developed a particular mathematical model based on that theory and applied it to Cassini data;) of self-gravity wakes;
2. Application of that theorymodel to the data produced a prediction for a future observation;
3. July 25 comes the test of the theorymodel which will either confirm or refute the theory.
My guess is that there will be good, but not perfect, agreement between prediction and observation. This would then lead to some modification of the self-gravity wake parameters that I have previously calculated. We will be back at step 1 with an improved model of the ring. Check out the prediction and check back in a couple of weeks to see how well I did.
Tation vs Tion
Thursday, July 13th, 2006Following on the “fragmentation” post, can you come up with words that, like fragmentation, segmentation, documentation, and regimentation get the extra “ta” but do not have roots ending in “ment” (like fragment, document, etc.)? Post them here as comments. I have thought of two so far.
The Trouble with Fragmentation
Wednesday, July 12th, 2006As a planetary scientist studying the formation of the planets and the evolution of planetary ring systems, the following terms referring to how a swarm of colliding objects (like ring particles, or asteroids, for example) evolves:
Accretion
Aggregation
Coagulation
Compaction
Fragmentation
At a meeting today of the Cassini UVIS science team, when this list of words appeared on the screen I was distracted from the subject by what appears to be an extra syllable. You see it, don’t you? It’s taunting us, or should I say “ta”unting us, there in the middle of “fragmentation”. Examining the rest of the list we see that accrete becomes accretion, aggregate becomes aggregation, coagulate becomes coagulation, compact becomes compaction, so why can we not have a fragmention? Is it unspeakable, or simply unmentionable? What is wrong with a frag? For that matter, how about segs? We have segmentation, but never is a seg mentioned.
So before the termination of this post I’d like to mention not only a frag and a seg, but also an imple, a regi, and a docu; those poor neglected prefixes that never get a mention.