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What you need to know for 06/23/2017

Star Talk: A celestial explanation for the Titanic disaster

Star Talk: A celestial explanation for the Titanic disaster

There were an unusual number of icebergs in the North Atlantic in early 1912. Might the moon have be

April 14, 1912, was a moonless night. By the time the moon rose just before dawn the next morning, more than two-thirds of the people aboard the Titanic had perished.

Had moonlight been shining over the sea that fateful night, the crew’s lookouts might have been able to see the deadly iceberg much sooner. Yet, there were an unusual number of icebergs in the North Atlantic that season. Might the moon have been responsible for unleashing these icy hazards?

The story starts three months earlier when there was a rare alignment of Earth, moon and sun for the first time in more than a thousand years.

Earth is constantly being tugged on by the gravity of the sun and moon. These forces pull across the entire planet, and the side of Earth that faces one or both of these objects experiences a slightly greater pull than the other side. The difference in this force of gravity from one side of Earth to the other is called the tidal force.

Water tides are the most easily noticed effect of the tidal force, but tides also occur within Earth. It’s like pulling on a rubber band; not only does it stretch along its length but it also narrows along its width. Similarly, the sun and moon squeeze Earth — the moon because it is close and the sun because it is so massive.

Impact of moon’s orbit

Every month as the moon orbits Earth, it does so in a path that is not circular but slightly out-of-round. Tidal bulges — where Earth is stretched outward toward and away from the moon — follow the moon around in its orbit. When the sun, moon and Earth all line up as they do at full or new moon, the tidal forces of the sun and moon across Earth combine.

The result is elevated high tides and lower than usual low tides. This happens twice a month, once at new moon, then two weeks later at full moon. These are known as spring tides. The name is derived from a German word meaning “to rise up,” and therefore has nothing to do with the spring season.

Since the moon’s orbit is slightly oval, roughly every six to seven months a new or full moon will occur when the moon is near its closest approach to Earth. This alignment will make spring tides much higher than usual. Technically, these are termed perigean spring tides because the point in the moon’s orbit nearest Earth is called the perigee.

However, a very rare situation takes place when the new or full moon occurs at or near its closest approach to Earth and the planet is at its closest to the sun. For these factors to occur together is exceptionally rare, yet this alignment happened on Jan. 4, 1912. To find a time when the moon was closer, you would have to go back to 796 or forward to the year 2257.

Could the extreme tidal forces of January 1912 caused by the sun and moon acting together on Earth make more icebergs break off the glaciers north of the Titanic’s path and set these ’bergs adrift?

Titanic problems

The glaciers along the west coast of Greenland are a prolific source of icebergs in the North Atlantic. If an iceberg were to detach from these glaciers and drift south, it would take at least five to six months, not the three months since January, to reach the path taken by the Titanic. A further complication is that the water currents along Greenland’s west coast flow north to Baffin Bay, where these floating hazards spend the winter. On the western side of Baffin Bay, the water currents flow south along the coast of Labrador and Newfoundland, where these ’bergs usually spend a second winter before reaching the northwestern part of the Atlantic Ocean.

As these icebergs float along the east coast of Labrador and Newfoundland, many drift aground in shallow water or are beached as the tide retreats. A stranded iceberg will slowly melt in place but a grounded one could eventually refloat when a high tide comes in. It will then resume its southward motion.

Rather than the very unlikely situation of an iceberg breaking off the west coast of Greenland and rapidly drifting south into the path of the Titanic, a much more plausible scenario is that the extreme perigean spring tides of January 1912 set many grounded, and possibly even supposedly stranded, icebergs afloat and back into the southward Labrador Current. This also explains the uncharacteristic number of icebergs that season.

On Jan. 4, 1912, a full moon occurred just six minutes before the moon’s closest approach to Earth. A month before, on December 6, 1911, a full moon occurred 22 hours before lunar perigee and a month later, on Feb. 2, 1912, a full moon happened 22 hours after its closest approach to Earth. This series of perigean spring tides, combined with the extreme perigean spring tide in early January 1912, probably refloated many southerly icebergs, allowing sufficient time to reach the Titanic.

Although we will never know the exact path of the iceberg that struck the Titanic, the moon — or more so its absence — did play a role that tragic night one-hundred years ago. The first words of Titanic survivor Second Officer Charles H. Lightoller spoke before a British inquiry concerning the events of that night were: “In the first place, there was no moon.”

April sky

Venus will continue to brighten in the twilight western sky during the next month and, for the first few days of April, Venus will be just under the Pleiades star cluster of Taurus. After mid-April, a view of Venus through a telescope will show that it is taking on a crescent shape as its orbit swings it closer to Earth.

Jupiter appears lower in the western sky than Venus, and it will be setting earlier each evening so that by the end of April Jupiter will set less than an hour after sunset. Mars is almost halfway up the sky in the east-southeast as the sky gets dark and is unmistakable by its yellow-orange color. Saturn is presently rising about two hours after sunset; it can be found against the stars of Virgo, just east of its bright star, Spica.

The crescent moon will appear to the upper right of Jupiter this evening and be to the left of Venus tomorrow. On April 3, the moon will be to the lower right of Mars and adjacent to Spica and Saturn three days later.

Richard Monda is an astronomer living in the Capital Region.

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