1 . While most people don’t think much about garbage, trash (垃圾) is beloved by archaeologist (考古学家). A favorite site for study is a midden (贝丘), an old trash or garbage heap (堆). A midden might contain damaged stone or metal items, which tell us about the weapons and tools people used. Softer materials such as wood, cloth, leather, and baskets are sometimes preserved. They may tell us what people wore, how they carried things, or the kind of toys used by children. Historic household trash heaps often contain broken pottery pieces and even traces of the food they once held.

Most people no longer keep a trash heap by the kitchen door. Instead, garbage is hauled off to landfills (垃圾填埋池). These landfills can still attract archaeologists. The Garbage Project collected information from landfills from 1987 to 1995. Student archaeologists measured tons of garbage from 15 landfills across the United States and Canada. This garbology, the study of garbage, research led to a better understanding of how people have changed what they consume during this period of time. The findings also led to a better awareness of how quickly various items rot. This helped with city planning for garbage disposal and recycling efforts.

Some found objects that may clearly be of archaeological interest, such as arrowheads and spear points. It is typically against the law to collect these on public lands, so they should be left in place. If you take a photo and note the location, you can notify the state archaeologist or the government branch that is in charge of the land, such as the National Park Service or the Bureau of Land Management.

Everyone is responsible for protecting archaeological resources, which is a concept known as “archaeological stewardship.” Sometimes this even means protecting old garbage.

2 . “How do they walk in these things?” complains Jack Lemmon, walking with difficulty in his heels, newly dressed as his another identity Josephine, in the film “Some Like It Hot”.

High heels were, in fact, originally designed for men — and had an extremely practical purpose. Soldiers on horseback wore them in 10th-century Persia, according to Elizabeth Semmel hack of the Bata Shoe Museum in Toronto. The heel helped keep them stable as they stood up in their stirrups ( 马镫) and took aim at enemies with bows and arrows (cowboy boots still use heels in this way). Over time, heels appeared on the shoes of male nobles across Europe. Yet from the mid-17th century, heels became associated with supposedly “feminine” qualities, and so became women’s wear. Until the mid-20th century heels were heavy, heavy things. After the Second World War, techniques and materials used in aircraft engineering were applied to shoes, creating the stiletto ( 细高跟). The high, narrow heel requires a thin metal pole, strong enough to bear the wearer’s weight yet flexible enough to allow the shoe to move.

Shoemakers have searched actively for a right heel. They aim to reduce the angle created by a high heel, which forces the few square centimeteres of the ball of your foot to bear the entire weight of your body. Joan Oloff, a podiatrist-turned-shoe-designer, makes footwear lined with memory foam ( 泡沫) to absorb the shock of each painful step. The bottom part of the shoe is crafted to support the arch of the foot and distribute the wearer’s weight more equally. Antonia Saint Dunbar, an entrepreneur, makes shoes with a heel cup and strips inside to stop the foot slipping around and getting blisters ( 水泡). And growing numbers of companies make shoes with adjustable heels: two inches for the boardroom, four for the nightclub, none for home.

However, the wisest are stepping down altogether: in 2016, for the first time, more British women bought trainers than heels.

3 . Early people didn’t need to know the exact time of day. They slept when it was dark and worked when it was light.

33,000—28,000 B.C.

People notice that changes in the weather (the seasons) are connected to changes in the sun, moon, and stars.

8,000 B.C.

Chinese, the Maya, and Sumerians develop calendars based on the cycles of the sun (a year) and the moon (a month). Most people are farmers. Calendars tell them when to plant crops and when their animals will have babies.

1,500 B.C.

People in Egypt and Sumer develop some of the first water clocks. Unlike sundials, water clocks measure time even when it’s cloudy.

1370—1410

European cities build towers with mechanical clocks inside. Every hour, a bell is rung for all to hear.

1850

Most Americans now have clocks at home. Trains keep exact schedules. Railroad workers carry pocket watches that don’t gain or lose more than 30 seconds in a week.

1955

An atomic clock is built in England. It measures oscillations(颤动) of light from cesium atoms. The light oscillates even faster than quartz crystals. Atomic clocks are the most accurate clocks yet.

Today

People rely on the Internet and cell-phone networks, which need super precise timing. Atomic clocks keep getting better.