【推荐2】Despite being one of the most famous and frequented attractions in the United States,     1    . Here are a few facts about the Grand Canyon you probably don’t know.

We don’t really know how old it is

It has long been believed that the Colorado River began carving the Grand Canyon about 6 million years ago,     2    . It suggests that the process may have begun as far back as 70 million years. In all likelihood, the Grand Canyon as we know it today started out as a series of smaller canyons 70 million years ago, but the majority of the canyon did not begin to take shape until much more recently.

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Of all Grand Canyon facts, this one is pretty cool—no word-play intended. Sudden changes in altitude have an enormous impact on temperature and rainfall, so the weather you are experiencing could differ dramatically, depending on where you are in the Grand Canyon. The coldest, wettest weather station in the region is the Bright Angel Ranger Station on the North Rim, while the hottest (and one of the driest) is just 8 miles away at Phantom Ranch.

There are lots of fossils in the area

While the dinosaur might have missed out on seeing the Grand Canyon, lots of other fossils have been found.     4    . They vary from ancient marine fossils dating back 1.2 billion years to fairly recent land mammals that left their remains in canyon caves about 10,000 years ago.

Fish are relatively uncommon in the area

Prior to modern flood control measures, the Colorado River provided a uniquely difficult habitat for fish, with heavy mud with small rocks, frequent floods, and temperatures ranging from extreme heat in summer to sub-freezing in winter. Consequently, only eight fish species are native to the Grand Canyon,     5    .

【推荐2】The history of life on earth has been a history of interaction between living things and their surroundings. To a large extent (程度), the physical form and the habits of the earth’s vegetation and its animal life have been shaped by the environment. Considering the whole span of earthly time, the opposite effect, in which life actually modifies its surroundings, has been relatively slight (轻微的). Only in the present century has one species—man got significant power to change the nature of his world.

During the past quarter century this power has not only become increasingly great but it has changed in character. The most alarming of all man’s assaults (侵犯) upon the environment is the contamination (污染) of air, earth, rivers, and sea with dangerous and even deadly materials. This pollution is for the most part irrecoverable. In this now universal contamination of the environment, chemicals are the wicked partners of radiation (辐射) in changing the very nature of the world, the very nature of its life.

It took hundreds of millions of years to produce the life that now lives on the earth. Given time not in years but in millennia (千年), life adjusted and a balance has been reached. But in the modern world there is no time.

I don’t mean that chemical insecticides (杀虫剂) must never be used. However, we have to admit that we have put poisonous and biologically harmful chemicals indiscriminately (恣意地) into the hands of persons largely or wholly ignorant of their possible harm. We have forced enormous numbers of people to contact these poisons, without their permission and often without their knowledge. We admit, furthermore, that we have allowed these chemicals to be used with little or no advance investigation of their effect on soil, water, wildlife, and man himself. Future generations are unlikely to forgive our lack of concern for the integrity (完好无损) of the natural world that supports all life.

【推荐3】Many airlines overbook their flights — meaning they sell more tickets than there are seats on the plane. But why do they do it, and what happens to passengers who arrive at the airport only to learn that their seats are already taken?

Like any business, airlines want to make money. So, they try to fill as many seats on each plane as possible. After all, empty seats are a financial loss on airlines.

Airlines look at data from past flights to predict the number of expected “no-shows”, passengers who canceled their flight, don’t show up or arrive late because of the connecting flights. For example, if the data shows that eight people normally don’t show up for flights from New York to Los Angeles, the airline might sell eight extra tickets.

However, the airlines sometimes get their numbers wrong. If there are too many people and not enough seats, the airline may ask passengers to volunteer to take a later flight for compensation (赔偿) — which might include money, travel vouchers (优惠券), free meals and hotel rooms. Some airlines have offered as much as $10,000 to get people to volunteer. However, if there are no volunteers, airlines may have to make passengers give up their seats. This is called “bumping”.

Although there’s no exact science, it’s often the lowest fares that get bumped to the next flight first. This means those flying business class or first class are highly unlikely to be bumped. Airlines have also admitted to bumping people based on the time of check — in arriving last minute is not recommended. Certain groups are less likely to be denied boarding due to overbooking, such as frequent flyers, the elderly, families with young children and people with disabilities.

In the US, if a bumped passenger is able to arrive at their destination less than an hour late using another flight, no compensation is required by law — although airlines may offer some. If they arrive over two hours late, the law requires that they be given 400% of the one-way ticket price, up to a total of $1,550.