## Posts

Showing posts from February, 2013

### Sunday fun day at Leo Carillo State Beach (An Erin report)

We broke from our routine of having mellow Sundays and headed out for a family adventure! The day's journey lead us up the Pacific Coast Highway to enjoy a windy winter day at the beach. We explored tide pools and caves, walked on the beach, slid down steep sand dunes and even spotted some sea urchins and sea stars (don't you call it a starfish!) until our hunger took over. We made our way to Neptune's Net for a delicious seafood lunch - ordered a sampler platter and dug in.

### Beware the slippery slope of marriage equality

Eclecta Blog puts forth fairly compelling arguments for non-traditional marriage (via Dan Savage):
In these instances, I’m reminded that the tradition of marriage is so sacred to many Americans that the notion of Republicans being allowed to marry can offend their very being. “Imagine,” their smoldering eyes seem to be screaming, “My dear, normal child being forced to sit in a classroom being forced to learn about Newt Gingrich’s belief that marriage should only between a man and a woman who doesn’t have cancer.” I'm usually pretty tolerant, especially when it comes to issues of marriage. But I don't know about this one. What's next, letting Tea Partiers marry each other? Can you imagine it? Just...yuck.

Personally, I believe we should let the states decide whether republicans can marry other republicans. That is, unless the states vote in favor of letting them marry. In that case, I believe in turning to state referendum, funded by rich people outside of the state, like w…

### 0.5 per year

0.5 year$^{-1}$. That's how many black americans earn Ph.D.s in astronomy each year. I was two years worth of data back in 2007. One of my primary goals as a professor is to increase that number to > 1 year$^{-1}$. An order-of-magnitude increase would do nicely.
During the summer of 2011 I had the pleasure of working with an outstanding young, black astronomer named Keith Hawkins. Here's an article about him that was featured on the Caltech website describing how he became interested in science and what he was working on with me and my student Tim Morton.

Keith is one of the best students I have worked with as part of Caltech's SURF/MURF program, and I'm proud to announce that Keith was awarded a prestigious Marshall Scholarship to pursue his Masters degree in astrophysics (M.Phil) at Cambridge University in England. Keith was one of three African American students, and one of 40 total students to win a Marshall scholarship this year.

Nice work, Keith!

### The science of comic books

Ph.Detours and PhD TV are at it again. Owen and Marcus are WAY into the various Peanuts movies, and walk around saying things like "Good grief!" and calling each other blockheads. This video gave me the idea of buying them some Peanuts comic books.

### This Week's Astro Nutshell: How Many Photons?

(Actually, this is from Astro Nutshell two weeks ago)

Each week I work with first-year grad students Marta and Becky on "order of magnitude" problems at the blackboard. I put that in quotes because we tend to do many more scaling arguments than true OoM. The idea is for them to draw on what they've picked up in class and apply it to common problems that arrise in astronomy.

How many photons per second per cm$^2$ (photon number flux) do you receive from a star as a function of its temperature $T$, radius $R$ and distance away $d$?

Having such an equation would be extremely handy for observation planning. When determining the feasibility of a new project, observers tend to start with a statement of the expected signal-to-noise ratio (SNR) for an observation of an astrophysical object. In the limit of a large expected number of photons, the signal is the number of photons $S = N_\gamma$, and the noise can be approximated as $N{\rm oise} = \sqrt{N_\gamma}$. …

### Giant Meteor Explodes Over Russia

From CNN via Jonathan McDowell (@planet4589)
A huge meteorite [sic] flared through the skies over Russia's Chelyabinsk region early Friday, triggering a powerful shock wave that injured nearly a thousand people, blew out windows and reportedly caused the roof of a factory to collapse. Multiple amateurvideos posted online showed the meteor’s flaring arc across the western Siberia sky. Others from the scene included the sound of a loud boom, followed by a cacophony of car alarms. One video showed the hurried evacuation of an office building in Chelyabinsk. “There was panic. People had no idea what was happening. Everyone was going around to people’s houses to check if they were OK,” Chelyabinsk resident Sergey Hametov told The Associated Press. “We saw a big burst of light then went outside to see what it was and we heard a really loud thundering sound.” Videos here: http://www.salon.com/2013/02/15/footage_from_the_meteor_crash/

### The Faculty Search Process

Here's an excellent Wiki page and post over at AstroBetter describing the faculty hiring process.
For a postdoc seeking a tenure-track academic job, the process can be mysterious, confusing, and sometimes terrifying (at least it was for me). The level of competition is known to be extreme, and there are a number of steps, including the selection of letter writers, the decision where to apply, how to craft your application essays and how to conduct interviews. There can be long-term consequences of how you approach early steps in the sequence, so it is useful to know ahead of time all the relevant steps in the application process and to start thinking critically and making some decisions. Big ups to proto-Prof. Josh Pepper for getting this wiki started (actually, he's in the rare, short-lived transitional phase). Also, big ups for the best professional profile pic evar:

### Do you see the Matrix? Derivation of Linear chi^2 minimization

This blog post is primarily for my Ay117 students. However, if you've ever wondered where chi-squared minimization comes from, here's my derivation.

Yesterday in class we reviewed the concept of "chi-squared minimization," starting with Bayes' Theorem
$P(\{a\} | {d}) \propto P(\{d\} | {a}) P(\{a\})$ In other words, if we wish to assess the probability of a hypothesis that is expressed in terms of the parameters $\{a\}$ conditioned on our data $\{d\}$, we first calculate how likely we were to get our data under the hypothesis (first term on the right), and multiply this "likelihood" by our prior notion that a given set of parameters is representative of the truth.

Supposing that we have data that are independent from one another, and normally distributed, then our likelihood term can be written
$P(\{d\} | {a}) = \prod_i \frac{1}{\sqrt{2\pi \sigma^2}} \exp{\left[\frac{1}{2}\left( \frac{y_i - f(x_i)}{\sigma_i}\right)^2\right]}$ As for the priors, we'll…

### Modern Professing

Erin gave me a profound insight this morning. The idea of being a professor used to entail "professing." Yes, we still profess today. But in the past, the professor was the one person, or one of only a few  people in the world who had expertise on a specific area of study. If you wanted to understand the nature of young stars and you were a student in the 1960's, George Herbig was one of only a few people in the world who could profess on the topic.

These days, things are very different. If you want to know about young stars (or planets, or galaxies, or any other topic) you can do a Google search and you'll find a Wikipedia page, a slew of PDF documents, and a bunch of crap. You could also go down to your library and find numerous books, or you could turn to NASA ADS and turn up hundreds, if not thousands of papers. The availability of all of this information in the modern age is orders of magnitude beyond what was available in 1970, but the sheer volume, variety an…

### Ask A Prof: To Post or not to Post?

I'm going to prototype a new series, which may spawn a separate blog, called Ask a Professor. The idea is that I get tons of questions about careers in science, and often I get the same questions from different people. So I figure I can broadcast the advice I can offer. Any question for which I can't give a good answer, I know lots of people who I can ask, and we can learn together in those cases.

IfA last-year grad student Brendan Bowler asks: "To post, or not to post; that is the question. That is, to the Rumor Mill.  Does it have any actual influence (either beneficial or harmful) on the  decision-making process of fellowship committees?"

One thing I can say right off the bat is that this question stirs a lot of strong and passionate opinions among professors (and postdocs, and students). For this question, I think I'll present my own opinion and then revisit the question after talking to some other profs. Also, if you have a strong opinion one way or the other,…

### Heavy, wet and energetic

Whenever the Moon's tidal field and the Earth's rotation  wind and land conspire to pick up the ocean and violently fold it over on itself, most people stay far away. A select few take the opportunity to slide merrily along the folded ocean on little boards, at the mercy of gravity and fluid dynamics.

Check out the video below and recall that there a little less than a metric ton per cubic meter of water. That's a lot of cubic meters of water over each surfer's head! I have no idea how a human survive having all that water savagely dumped on them. h/t Jon Swift.

### Ask a Professor: How does a prof spend their time?

I'm going to prototype a new series, which may spawn a separate blog, called Ask a Professor. The idea is that I get tons of questions about careers in science, and often I get the same questions from different people. So I figure I can broadcast the advice I can offer. Any question for which I can't give a good answer, I know lots of people who I can ask, and we can learn together in those cases.
This week's question is from Molly Peeples (UCLA), "What does a professor do all day?  I think most postdocs realize it's some combo of research+teaching+advising+committees, but don't realize how a faculty meeting can go for hours or how committee obligations (both within the department/university and broader community ones) are capable of sucking up so much time."

Well, as an observer, my answer to most problems is: We need some data. This case is no different, and fortunately I have the perfect data set to address this question. Way back in 2009 at the previou…

### Lake-front property, expansive view of faint, red sun that never sets

Yesterday, I had the honor of participating in a live press conference today at the Harvard Center for Astrophysics (CfA). The event was to announce new findings by third-year graduate student Courtney Dressing and her advisor Dave Charbonneau, who studied the occurrence of planets around M dwarfs in the Kepler field. Dear Sara Seager, check it out! A woman with not only a big exoplanet press announcement, but a HUGE exoplanet press announcement! (But, yes, we need more).
Sound familiar? If so, it's because Jon Swift and I made a related announcement last month at the AAS meeting. But while we focused ont he bulk occurrence rate, finding 1.0 +/- 0.1 planets per M dwarf, Courtney focused on Earth-like planets. By Earth-like she means, "planets the size of the Earth that receive a similar amount of sun light as our planet." (As an aside, Jon and I were very much relieved and excited that Courtney's statistical analysis matched our result on the bulk occurrence rate.)

### #2body goto Fark!

Whoa! My first time on Fark. (h/t Chuck)

It sparked a good discussion, too.

### On the Two-Body Problem

In academia there is something called the "two-body problem." The original two-body problem involves the gravitational interaction between two massive bodies, e.g. a planet orbiting a star. This is a problem in the mathematical sense, as in something interesting about the universe that we would like to figure out. This classical two-body problem has a solution, but interestingly it is in the form of a transcendental equation that can only be solved numerically. But when done so, it looks like this. Pretty nice, huh?

It turns out that there's an even more difficult two-body problem in science academia, but this one has to do with the attraction between two humans (cf Figure 1 above for a succinct description). The problem arises when one or both individuals are academics seeking post-graduate job positions. The problem, in a traditional sense of the word, is related to the fact that academia has been honed and perfected over the centuries to accommodate only a specific typ…

Sometimes you get sick and you're all, "Whoa! Where'd that come from?" That's how I felt two weeks ago when I came down with some weird stomach virus. Fortunately, the whole thing was over within 48 hours.

Other times you start to sniffle, ache and sneeze and you're all, "Yep. I pretty much knew that was coming." In fact, on some of these occasions you can remember the exact moment in space-time when the disease was transmitted to you. Those times most frequently involve kids.

I love my children with a white-hot intensity equal to that of the Sun's core. However, dammit if they aren't the most effective disease vectors known to man. Ticks? Psht. Mosquitoes. Please.

Take tonight, for instance. I can feel the early stages of the flu coming on. My eyes burn, I'm coughing and I'm getting more and more weary every passing hour. I know how this happened. I was sitting in the living room Friday when Owen, who had been sneezing all day, star…

### The upside of procrastination

I've long wondered about the problem arising at the intersection of interstellar space travel and Moore's Law. Moore's Law is an empirical rule that states that technology doubles in speed (or other metric) every 18 months. The laptop that I'm typing this post on right now will be half as fast as the next Macbook Pro 18 months from now.

I doubt I'm the first person to think about this, but imagine a large crew of space settlers at the halfway point to alpha Cen. They might be the second or third generation aboard the space craft, having known nothing but their trip to the nearest stellar system. Out comes the bubbly, but in the middle of the celebration there's an announcement: "Captain, there's something showing up on our radar, approaching fast!" As the object flies by, the crew can just make out the relativistically shortened form of a brand-spanking-new, next-generation space craft, zipping past using the latest technology on the way to alpha …

### C'mon U Penn!

The senior faculty of the Department of Africana Studies recently RSVP'd to U Penn's annual diversity dinner, saying thanks, but no thanks to this year's event (h/t Claude). The reason is that at last year's dinner they demanded to know why the president had not appointed a single minority to the upper administration during her tenure.
Her response was that she would not just bring in someone who is not qualified, a comment implying that none of the people in the room were qualified to serve in these positions, even though many of them serve in administrative capacities in departments and centers. In her closing remarks, President Gutmann reiterated her dedication to diversity within Penn’s administration, admitting that “a show beats a tell.” President Gutmann’s “show” came on Jan. 17, when she announced the appointment of the new dean of the School of Arts and Sciences. Yes, a show beats a tell every time, and once again, she has shown that her commitment to diversit…

### Astro Memories

Sometimes I try to remember specific events from my recent past, say in grad school, and I can't remember the dates, ordering of events, and other details. It's amazing how 10 years can smear out important details in your memory. However, there's one event that I can clearly remember and even assign a specific date to. On the eve of the start of the Iraq war back on March 19, 2003, I was driving from Hale Pahaku to the summit of Mauna Kea, from 9000 feet to 14,800 feet. Prof. Mike Liu was driving and Mike Fitzgerald and I were passengers of the CFHT-issued Chevy Suburban. BBC radio was on and I was listening to reports of bombs falling on Bagdad, with a sinking feeling in my gut. Both because of the realization there was nothing I could do to stop my country from getting into the war, and because of the ride up the mountain.

What I remember very vividly was Prof. Liu had that Suburban was going very quickly along that Mars-terrain-like road. I remember the date, the peopl…