Tuesday, November 23, 2010

Matt Welsh Leaves Harvard for Google

In his blog posting he discusses leaving his academic post for Google.  He's also written a nice post about things to consider before starting on a PhD.  It's slightly computer science focused, but generally it's all very much on target!

Monday, November 22, 2010

Blue Moon Definition Was Wrong

From a Space.com article by Joe Rao.

I was wrong.  My wife said last night that the moon was a blue moon.  I said, that's not possible because a blue moon is a second full moon in the same month and that couldn't happen on 21 Nov.  It has to happen at the very end of a month.  She pointed me at the above article that explains it.

The short answer is that the two full moons in a month definition is actually erroneous.

Rao notes that Lawrence J. Lafleur, in Sky and Telescope in 1943, quotes a 1937 edition of the Maine Farmer's Almanac, stating that a blue moon is the rare occurance of four full moons in a season instead of three.  The blue moon is the third moon in that season.

The mistake was apparently made by James Hugh Pruett in a 1946 Sky and Telescope where he misinterpreted Lafleur's explanation to mean a second full moon in a single month.  (See the above article for details).

The wrong explanation was propagated by Deborah Byrd in the radio program “Stardate” in 1980 and then the wrong definition, quoting Rao, “went viral.”

It all makes me wonder when I first learned of the two-full-moons-in-a-month definition.  I would have thought it was long before 1980, but maybe it was after that date.

Well it sort of spoils the whole thing.  Now we'll have to talk about old-correct-definition blue moons and new-incorrect-definition blue moons and none of them will seem quite right any more.

This would all be a lot simpler if the moon would just actually turn blue once in a while.

Friday, November 12, 2010

Thirty Years Since We Watched Voyager on TV

I was the director* of the planetarium at the time and had received a letter from NASA that they were broadcasting live coverage of  the Voyager 1 encounter via satellite.

When I was a kid, reading library books about the solar system, there would often be a chapter at the end of the book on the Grand Tour of the Planets.  A favorable alignment of the four gas giants, Jupiter, Saturn, Uranus and Neptune, would allow a single spacecraft to visit each of them using gravitational assist, in the distant future of the 1980s.

Fast-foward to 1977, either 5 Sep 1977 (Voyager 2) or 20 Aug 1977 (Voyager 1), I forget which.**  It's morning and I'm lying on the sofa after being at the museum's observatory all night.  I'm watching the Voyager spacecraft launch on TV.  With those launches, the Grand Tour became a reality and Voyager 2 visited all four planets.

However, it was Voyager 1 that visited Jupiter and Saturn first.   The spacecraft stole some of Jupiter's orbital momentum, causing Jupiter to fall just a little bit toward the sun, as it accelerated on to Saturn

 The event was going to happen on 12 Nov 1980.  There was no NASA channel at the time so I had to call the local cable operator (Cox) and ask them to tune into the particular satellite and transponder that NASA had arranged and to feed the coverage out over a spare channel on their cable plant.  It took some convincing since they were reluctant to actually commit a channel, even for a one-time event.  In the end, I think I ended up talking to a guy in control shack, probably running their dish farm, who didn't seem to want to be bothered with events from other planets.  My memory is that I never got an absolute firm commitment, but something more like a shaky okay, which was more than a little worrisome.

Next, it was necessary to find a video tape recorder and it turned out there was one I could borrow from the board of education.  I drove down to their dusty equipment warehouse to pick it up.  Or maybe it was just the road by the warehouse that was dusty.  It was an old 3/4-inch U-Matic machine, a video cassette size that was heavily used by TV stations in those days.  The 1/2-in cassettes were just starting to become popular as the VHS vs. Betamax battle was raging.

We hauled the recorder over to one of our staff member's parents' house  to record the coverage, since they had cable.  The encounter was in the middle of the day and several of the planetarium staff were crowded into their den, watching the show.

It was a heady time indeed as we watched those black and white pictures scroll slowly in (because the data download rates from the space probe probably slower than the modems of the time!).  Of course they were not digitally post-processed yet—they were pretty raw images, so there were just the beginning hints of some of the amazing sites to come.  The coverage cameras showed ecstatic scientists watching the same images appear on their control room monitors and there were several interviews with Ed Stone, Carl Sagan and others who were seeing their own life-long fantasies come true.  Sometimes you suddenly arrive at those moments when you get goosebumps and a lump in your throat, when you know you're experiencing pinnacle achievements in human history.  This was one of them.

As the pictures crawled in, I believe it was possible, even in those first images, to see the spokes in the rings, the braided F-ring, and some of the other jaw-dropping, never-imagined features of Saturn up-close.

After recording the fly-by, we borrowed a TV from one of the local TV stores (yeah, it's weird to recall that there actually were TV stores then***).  It was just a standard 19-in CRT or it might have been larger.  We set it up in the planetarium and opened to the public for a replay of the “live” Voyager-Saturn encounter.  I remember we had a bit of difficulty because the video tape recorder had a separate RF modulator that had to be physically plugged into the back of the machine (think small, chunky game cartridge) before we could get a signal to the TV.

I guess we had enough lead time to advertise the event using the usual TV and newspaper avenues because I remember a pretty good turnout.  There were college professors, amateur astronomers and many other enthusiastic folks from the community there who were just as thrilled as the crew at JPL to see these first images coming back from the ringed planet, even though our replay was delayed by hours.

As I recall there were encounter events over two or three days as Voyager flew by some of Saturn's moons and made its way across Saturn's “miniature solar system,”  so we had probably two and possibly three nights of replay.

Today Voyager 1 is over 115 AU (astronomical units) from the Sun.  By definition, the Earth is 1 AU from the Sun.  Pluto is, on average, 40 AU.  Voyager 1 is the most distant, active spacecraft in the solar system and it's still collecting and transmitting data.

“In four to six years, Voyager 1 is expected to cross beyond the heliosheath, the outer layer of the bubble around our solar system that is composed of ionized atoms streaming outward from our sun, ” reports a news release from NASA this past October.

We've come a long way from those solar system books from the library, written in days when artists never even thought to include clouds when illustrating the Earth as seen from space.  I've been amazed to see so many of those funny but always awe-inspiring artist's conceptions come to reality.  It will be fascinating to see which ones come next.


It was just past the turn of the century and I'd never thought about it before even after a couple of years or so.  It was a friend who pointed out to me that the two vehicles sitting in my driveway were a Voyager and a Saturn.

* Technically my title was curator at the time.  It was a few years later that we reorganized and all department heads became directors.  The main change was that we each gained full spending authority over our budgets.

** No that's not a typo.  Due to the solar system mechanics involved, Voyager 2 was actually launched before Voyager 1.

*** When I was a kid and the TV malfunctioned, a TV repairman actually came to our house to fix it.

Image Credit

Ghostly Spokes in the Rings

Scientists first saw these somewhat wedge-shaped, transient clouds of tiny particles known as “spokes” in images from NASA's Voyager spacecraft. They dubbed these features in Saturn's B ring “spokes” because they looked like bicycle spokes. An electrostatic charge, the way static electricity on Earth can raise the hair on your arms, appears to be levitating tiny ring particles above the ring plane, but scientists are still figuring out how the particles get that charge as they analyze images from NASA's Cassini spacecraft.

The image on the left was obtained by Voyager 2 on Aug. 22, 1981. The image on the right was obtained by Cassini on Nov. 2, 2008.

Image credit: NASA/JPL and NASA/JPL/SSI

Thursday, November 11, 2010

Demolition Goes Wrong

[VIDEO] I think the lesson is clear here: Don't let Ms. Johnson's Fourth Grade Class do your demolition.  Use professionals.

Note the video appears on this page from msnbc.msn.com.

Tuesday, November 09, 2010



In this article, Ian O'Neill at news.discovery.com describes how new data from NASA's Fermi Gamma-ray Space Telescope have indicated that gammar ray bursts are too energetic to be generated by magnetars and must come from black holes.

A magnetar is a neutron star, a highly compact object made up of degenerate neutrons, with an extremely strong magnetic field.

The largest stars undergo the most energetic supernovae producing either a massive, magnetically dominated neutron star (known as a "magnetar") or a black hole. It is thought that young magnetars are the key driver behind GRBs.

But a GRB is a very different creature to an 'average' supernova. Via a mechanism that is poorly understood, intense narrow jets of hot plasma are blasted from the dead star's rotational axis. Intense radiation is also produced. If one of those jets are pointing directly at Earth, we'll see an explosion that seems too powerful to be a supernova. That's a gamma-ray burst.

It would appear that in all cases too much energy is generated for the magnetar model to be valid.

"The magnetar model is in serious trouble for such incredibly powerful events," said coauthor Alex Filippenko, UC Berkeley professor of astronomy. "Even if the magnetar energy limit is not strictly violated, the tremendous efficiency required by this process strains credulity."

SSH: passwords or keys?

by Jake Edge 2010-01-13 at lwn.net.

The Three C’s of Social Content

Consumption, Curation, Creation by Brian Solis at briansolis.com. This is quite fascinating.

Monday, November 08, 2010

Eris Gets Dwarfed

Pluto may be the biggest Kuiper Belt object again.   Sky and Telescope has a news item by Kelly Beatty describing observations of an occultation of a 17th-mag star (named L1654635357407160223) by Eris set new and smaller upper bounds on Eris' size.

…successful observations from widely separated sites create two chords across Eris's shadow that yields a unique solution for its diameter (assuming that the object is spherical).

That number, according to Bruno Sicardy (Paris Observatory), is hard to pin down exactly because timings derived from the three telescopes' light curves have some uncertainty. Even so, Sicardy notes in an email, "Almost certainly Eris has a radius smaller than 1,170 km" — and that would make it ever-so-slightly smaller than Pluto, whose diameter is thought to be 1,172 (±10) km. Don't be surprised if the final value gets pushed another 50 or 60 km lower.
Previous observations were based on direct infrared measurements and size estimates were derived from assumptions about the surface brightness (albedo) and other aspects of the body.

Image credit:  Marselo Assafin and others.  From Sky and Telescope.

Saturday, November 06, 2010

How Search Works on Google

by Matt Cutts.  

Evolution of the Batman Logo


Herschel-ATLAS Finds Gravitational Lenses

Large numbers of unusually bright images in the far-IR which appear to be galaxies magnified by gravitational lenses in newly released data from the Herschel-ATLAS project

“Our survey of the sky looks for sources of sub-millimeter light. The big breakthrough is that we have discovered that many of the brightest sources are being magnified by lenses, which means that we no longer have to rely on the rather inefficient methods of finding lenses which are used at visible and radio wavelengths,” says lead researcher Mattia Negrello of the Open University.

Negrello says that “…Our results show that gravitational lensing is at work in not just a few, but in all of the distant and bright galaxies seen by Herschel.”

Tumblr, Twitter and Blogging

I just read the article Can Tumblr Topple Twitter by Paul Sawers and poked around Tumblr a bit more this morning.  One thing I realized about Tumblr is that it can look quite a lot like Twitter.  You can post brief, tweet-like messages and the page display (using one of the default themes) is quite clean and Twitter-like.

Add to this the searching function, the Reblog buttons, and the ability to follow other users, and you basically have Twitter.  Hm.

But, there's also the versatility of it being a blog with titles and of course much longer posts, if you wish.  Hm.

Looking at the default set of themes on Posterous, there's no doubt the thinking there is that this is purely a blog. All the themes and layouts look blog-like.

Of course there's nothing preventing you from posting short, subject-less posts of, say, 140 characters or less.