Watching an ocean wave running against the coast is beyond magical. But there is one type of wave — the cross sea wave — that is beyond anything you may have ever experienced. Although still attractive, cross sea waves are dangerous and have been responsible for many ship accidents.

Before we get into the physics of cross sea waves, let’s get to know how ocean waves are generated. The wind is mostly responsible for the creation of ocean waves. As the wind blows, it moves energy to the surface of the water, creating a constant disturbance (干扰) that results in a wave crest (波峰) . Waves generally run parallel (平行地) to the shore, but a cross sea wave is different. It’s created when the wind from two weather systems — one old, the other new — runs against each other.

Cross sea waves generally occur along coastal areas, and they are rare. Yet, there is one place along the west coast of France, where cross sea waves occur quite often. Because of the geology (地质状况) of the Isle of Rhé, it’s perfectly situated for their creation. The sight of the waves brings thousands of tourists to the island’s lighthouse each year.

When a cross sea wave blows, it will be difficult for boaters to control their ships or boats, as well as swimmers. Part of the reason why cross sea waves are so dangerous is that they generate powerful waves, which can reach nearly 10 feet (3 meters) high, more than enough to turn over a large boat.

Cross sea waves are usually found in shallow waters, such as those off the Isle of Rhé, and Tel Aviv, Israel. Since it is so exciting to watch the cross sea waves, these places attract millions of visitors each year, making them famous tourist destinations on Earth.

During its 300 or so years in Britain, tea has changed from the exotic to the ordinary. Historians like to ask why the Industrial Revolution took place here in the 18th century and not elsewhere in Europe or Asia. Several historians argue that sugar played a significant role in fulling workers. Could it be that sweet, boiled water with a mildly addictive plant produced a healthier as well as more energetic population just when England needed labour? That appears to be the case put forward by Francisca Antman, an economist at the University of Colorado.

It is not a new thesis, but Professor Antman provides the first quantitative evidence that tea drinking powered the Industrial Revolution, by increasing the health of workers. Her study reveals that the practice of boiling water for tea lowered death rates by 25% in lower water-quality areas. This “accidental improvement”, she argues, occurred just as people were moving into cities, where the crowding together would otherwise have led to serious epidemics. Instead, the country possessed a healthy pool of labour needed for industrialization.

One of the key moments that shifted tea from a luxury good to a mass market drink came, the Antman paper argues, in 1784 when the tea tax was cut from 119% to 12.5% at one stroke. By the end of the century, even the humblest farmer drank tea twice a day. The East India Company also muscled out an opponent coffee by pushing its tea in the home market. Tea gardens made the drink a cultural custom, as did the worker’s tea break.

Professor Antman argues, “Why England experienced a decline in death rates over this period without an increase in wages, living standards, or nutrition can be explained in part by the widespread adoption of tea as the national drink and increased consumption of boiled water”.