Introduction
Earlier this week, with the 100th anniversary of the sinking of the Titanic coming up next month (April 14, 2012), a new report is out claiming that the moon “helped” to sink the Titanic.
What this is really saying and what the media is trying to say and what the real effect may have been are all somewhat different things.
Tides
To understand the story, you need to know about tides. We can go back to Newton for his Equilibrium Theory of Tides and the people who improved upon it t get a rough background. In its simplest formulation, tidal intensity is not caused by the inverse-square law of gravity (the gravity from an object falls off as 1 divided by the square of the distance, so if you’re 2x farther away, the gravity is 1/4 as much), but rather an inverse-cube. So the closer you are to what would cause tides, the tidal effects are larger. Similarly, if you’re farther away, then they’re significantly smaller.
On Earth, tides are caused both by the moon and the sun. The sun’s tidal effects are only about 40% as much as the moon’s. If the sun and moon line up, then their effects combine and we get spring tides. If the sun and moon are at right angles (during a first or third quarter moon), then their combined effects are diminished and you get neap tides.
The other component of this story is that the moon is on a slightly elliptical orbit around Earth, and Earth is on an elliptical orbit around the sun. We’re closest to the sun in the month of January, and the moon’s closest point to Earth moves around with time.
The Basic Idea
The basic idea of this story is that the Titanic set sail (not that it had sails) in April, 1912.
On January 3, 1912, Earth was at perihelion – its closest approach to the sun. One day after that, on on January 4, 1912, the moon was full, and it was also (according to this work) at perigee (its closest approach to Earth). The Time article I linked to at the start of this post claims, “the moon just happened to make its closest approach to earth in 1,400 years.” That is not correct, since by definition, it must make its closest approach to Earth once an orbit. It might have been the closest approach at the most full phase in 1400 years, but that’s a different issue.
What this all means is that we had strong tides from the lunar and solar tides adding up (spring tides), and the individual components of each were particularly strong because the moon was its closest and we were closest to the sun.
What the authors (Donald Olson, Russell Doescher, and Roger Sinnott) of this study claim in the magazine Sky & Telescope (or what one of my former professors used to call “Try-and-sell-a-scope” due to all the ads), is that these particularly high tides affected iceberg migration patterns. They suggest that icebergs frequently become grounded in shallow waters around Labrador and Newfounland (Canada). The particularly high high tides could have freed some of them. Including the one that struck the Titanic.
Final Thoughts
To me this is a “just so story.” Yes, it’s possible. I don’t know how probable it is as it requires an unknown and uncharted iceberg being maybe freed due to high tides and then happening to be the one that struck the Titanic. There’s no way to prove it and I don’t think even the original authors are really saying “This IS what happened.” But the media is tending to report it that way.
In the end, it’s possible, and with the 100th anniversary of the Titanic’s sinking coming up in 33 days from writing this, I expect more kinds of stories about it to come out over the next month. The thing to remember about many of these “this could have happened!” stories is the “could” part. Maybe yes, maybe no. But you’re going to hear about them because that’s what the media does before some anniversary that they think will sell.
Exposing PseudoAstronomy 