Under the Microscope: During a recent general election someone remarked that Cork society is divided into two sections: the have-yachts and the have-nots. I am toying with the idea of joining the have-yachts set.
Whatever this might do for my social standing, I have discovered that sailing is a most pleasurable hobby for a scientist. Many components of sailing are underpinned by scientific principles, and some understanding of them greatly enhances the pleasure of sailing.
The most fundamental aspect of sailing is harnessing the wind to drive the boat through the water, particularly when sailing against the wind. We have all experienced, when walking, how a strong wind in the back pushes one along, but walking into the wind, at any angle, requires much effort. How can a sailing boat move against a headwind by harnessing its power?
The answer can be illuminated by a simple analogy. First of all, you cannot sail directly into a headwind. Picture your boat at the centre of a circle, facing a strong northerly wind. You want to sail to a point B due north on the circumference of the circle. The circumference is divided into 360 degrees. Point B lies at 0 degrees.
Your sailing boat will make no progress towards B if you aim it within 45 degrees on either side of 0 degrees. You can sail forward, however, by staying as close as possible to 45 degrees to the wind, sailing to the right or to the left. So you can make progress in a northerly direction and reach your destination B by sailing a zigzag course.
If you sail between 45 and 90 degrees into the northerly wind, the wind will blow sideways onto your sail, pushing your boat in a southerly direction. Protruding into the water beneath your boat, however, is a flat keel with a large surface area. This resists the force of the northerly wind.
It is like squeezing a bar of soap. The combination of the sideways force from the sail and the water resistance on the keel pushes the boat forward in a northerly direction of least resistance, just as soap slips forward when you squeeze it.
Other aspects of sailing of interest to the scientist include the tides and the weather. A good knowledge of tidal heights, directions and strengths is vital, particularly for coastal sailing. Tides are caused by the gravitational pull of the moon and the sun on Earth. Earth rotates daily on its axis and annually around the sun. The moon rotates around Earth each month.
We are familiar with the tidal cycle. The tide comes in and the water rises to the high-tide mark, then it recedes, and the water drops to the low-tide mark. We experience two high and two low waters a day, as Earth rotates.
There is also a monthly cycle of spring and neap tides. The spring tidal range is greater than the neap range - that is, a spring-tide high water is higher and a spring-tide low water is lower than a neap tide.
Spring and neap tides are explained by the relative positions of the moon, sun and Earth. When the pull of the moon and the pull of the sun oppose each other, we have neap tides. When the moon and the sun are in line with Earth, we have spring tides.
Weather is the result of temperature changes in the moist dense air that surrounds Earth. Radiant energy from the sun heats Earth and the atmosphere unevenly. Air exerts pressure on Earth's surface; we can measure it with a barometer.
As warm air is less dense than cold air it rises; then cold air sinks to replace it. This movement causes variations around the average atmospheric pressure, resulting in regions of relatively low and high pressure.
When air moves from a region of high to a region of low pressure we feel the movement as wind. Cool air sinks in a high-pressure area, usually producing dry, settled weather. Weather is usually disturbed in a low-pressure area because the air rises, cools and condenses into cloud, the rising air sucking in surrounding air to fuel the cycle.
A steadily rising barometer indicates good weather. A slowly falling barometer indicates rain. A rapidly rising or falling barometer indicates strong winds and probably rain. Anticyclones and depressions dominate the weather system in our latitudes.
In an anticyclone, the winds blow clockwise around an area of high pressure. Anticyclones are fair-weather systems and generally move slowly. A depression is a low-pressure area around which the winds blow anticlockwise. It indicates strong winds, unsettled weather and heavy rain.
The main air masses affecting Ireland originate from polar and subtropical regions. Tropical air is warm and can be wet or dry, depending on whether it has passed over the sea or a continent. Polar air is cold and can also be wet or dry.
A weather front is the boundary between two kinds of air. Most depressions that approach these islands form at the boundary between polar and tropical air masses.
I could go into much more, but I am out of space. If you are at a loss for something to do, take a course on navigation. In the Cork area, the International Sailing Centre in Cobh runs excellent courses.
• William Reville is associate professor of biochemistry and director of microscopy at University College Cork