Lunar and Otherwise

I have a great gig doing cruise ship enrichment presentations about astronomy.  Lots of good conversations flow after my talks, particularly at sunset when some of us gather on the top deck to wave goodbye to the Sun.  Sunsets at sea are some of my favorite scenes, so I always make time to enjoy them.

One of the questions I got from a passenger recently was about how he’d read that the survivors of the Titanic sinking in 1912 had looked up at the stars as they floated (freezing) in their lifeboats awaiting rescue.  I would imagine the view would have been spectacular in the chilly scene.  It’s interesting that people did mention seeing the stars, considering what a life-threatening situation they were in.  Maybe those things become more important when the end appears nigh.

Speaking of Titanic, there’s a theory afloat now (see what I did there?) about how a team of astronomers from Texas State Universe in San Marcos worked together with Sky & Telescope’s senior contributing correspondent Roger Sinnott, to figure out if the Moon played a roll in this infamous disaster.

Most of us know the story: the ship was supposedly unsinkable, and was steaming through an iceberg-ridden seas when it struck a huge chunk of ice, took on water, and went down, killing 1,500 people.  Those facts are unsinkable. Or unassailable, so to speak.  What the team found interesting, however, was that the Moon, along with the Sun and Earth may have played a curious role in the sinking.

Early in 1912, the Moon and Sun had lined up in such a way their gravitational pulls enhanced each other more than usual. That created a well-known effect called a spring tide, which was an unusually high tide. At the same time, the Moon was at perigee — that it is, it was at its closest Earth, and it was the closest perigee in 1,400 years. Perigee came within six minutes of a full Moon. To add icing to this orbitally dynamical cake, Earth had just passed through its own closest approach to the Sun (called perihelion) the day before. In astronomical terms, this was like the perfect storm of variables that may have contributed to another phenomenon:  many more icebergs clogging up the sea lanes that year.

How would this have happened? According to the Texas State group, the fate of the Titanic was sealed by the prevalence of  grounded and stranded icebergs. Icebergs calve off of glaciers in Greenland and take to the seas. As they travel south, many get stuck in the shallow waters off the coasts of Labrador and Newfoundland. Normally, icebergs remain in place and cannot resume moving southward until they’ve melted enough to refloat or the tide rises high enough for them to float free.  A single iceberg can become stuck multiple times on its journey southward, a process that can take several years. The unusually high tide in Jan. 1912 would have been enough to dislodge many of those icebergs and move them back into the southbound ocean currents, where they would have just enough time to reach the shipping lanes for that fateful encounter with the Titanic.

You can read more of this fascinating story in the April 2012 edition of Sky & Telescope magazine.