Climate Control of Dynasties
In the late ninth century a disastrous harvest precipitated (Adj,突如其来的) by drought brought famine (大饥荒) to China, ultimately ending the three-century rule of the Tang Dynasty. Climate change may have been a cause, according to a stalagmite from northwestern China. Composed of calcium carbonate leached （V,过滤） from dripping water, the stalagmite （石笋） preserves a record of rainfall in this region.
It shows that the vital rains of the Asian monsoon（雨季，季风） weakened at the time of the downfalls of the Tang, Yuan and Ming dynasties over the past 1,810 years. These times of strong and weak rains, when compared with Chinese historical records, coincide with periods of imperial turmoil （骚动，混乱） or prosperity, as in the case of the expansion of the Northern Song Dynasty, when harvests were abundant. In the past 50 years, however, industrial soot（煤灰，用煤灰弄脏） and greenhouse gases are causing the rains to weaken. Perhaps that is why today’s rulers of China are eager to act on climate change.
Sounds like Thunder
Conventional loudspeakers produce sound by vibrating back and forth, but new speakers made from sheets of carbon nanotubes（纳米管道， Nano 十亿分之一，及其微小的） create music the way lightning generates thunder. When an audio-frequency electric current was applied to stretchable, flexible transparent films of 10-nanometer-thick carbon nanotubes, physicists at the Tsinghua- Foxconn Nanotechnology Research Center in Beijing unexpectedly discovered they could make sounds as loud as commercial speakers. The scientists reason that the electrified nanotubes heat and expand the air near them, producing sound waves. These loudspeaker membranes can be stretched up to twice their original length without breaking and with little change to sound intensity. These sheets could be placed over paintings,
windows, video screens—even in clothing, the researchers say, as a means to keep a person warm. They even put their handiwork on a waving flag.