Pedagoguery

April 2012 is the 100th anniversary of the inaugural, and final, voyage of the Titanic, so I thought I would commemorate that event with a discussion of the role of the moon in that fateful voyage.

The most obvious role of the moon was its absence on the night of the collision with the iceberg. The night of April 14, 1912 was a new moon. Typically, lookouts of the day identified icebergs at night from the reflection of moonlight off of the foam breakers around the iceberg. Not only was that night moonless, however, but the sea was unusually calm, so there were few breakers to be seen. That, combined with the powerful engines and undersized rudder of the ship, meant that when a warning was finally given, it was far too late to turn the ship to avoid the collision.

However, the moon played a more indirect, but potentially more pivotal role in the disaster. On January 4, 1912, there was a rare confluence of events. The moon was full at that time, which always means stronger tides since at full moon and new moon, the lunar and solar tides combine in what is called a spring tide. However, the moon does not orbit the Earth in a perfect circle, and on that night, the moon was near perigee – the closest point in its orbit to Earth. In fact, the time of the full moon and the time of the moon's perigee differed by only 6 minutes. This yielded unusually strong spring tides. What's more, a mere 27 hours earlier, the Earth was at perihelion – the closest point in its orbit to the sun.

How would these extreme high tides have affected the Titanic? It was remarked at the time that there was an unusual number of icebergs in the north Atlantic shipping lanes in 1912. But to really answer that question, we need to take a look at where those icebergs originated. The icebergs in the western part of the North Atlantic most likely originated from the glaciers in western Greenland. Now, it is well known that the tides can affect calving from glaciers. The reason for this is simple: the end of the glacier lies over the water, and as the sea rises and falls, it produces stresses in the ice which cause it to crack. So, the high tides in January (as well as higher-than-usual high tides in December and February) could well have calved off a much higher than usual number of icebergs from western Greenland.

There is a problem with this theory, however. If the iceberg that sank the Titanic calved off in January, it would have had to have been traveling exceptionally fast to end up south of Newfoundland in just 4 months. The West Greenland Current actually travels northward into Baffin Bay, so newly calved icebergs typically head north before being caught in the south-bound Labrador Current. So, it is unlikely that the tides caused the calving of the iceberg that sank the Titanic.

However, if we look at the typical path of icebergs in that area, we notice something interesting. As they follow the Labrador Current south, many icebergs run aground. The Canadian Hydrographic Service has two categories of stationary ice: “grounded ice”, which are icebergs that have temporarily run aground but can be easily re-floated, and “stranded ice” which have been deposited high enough that the chance of re-floating is negligible. If we suppose that the iceberg that sank the Titanic actually calved in 1911 or 1910, then the high tides of the winter of 1912 could easily have re-floated quite a lot of grounded ice. This would account for the unusual number of icebergs in the North Atlantic shipping lanes that year.

While we will never know for certain from where that fateful iceberg originated, it is quite likely that the high tides of that year had a lot to do with it. This just goes to show how strong an influence the moon can have on us.

Next time, a look at the kinds of stars where we have found planets.