THERE is in Upper Thibet a plateau called the “Kyan Chu Plain,” on which phenomena of mirage are frequently seen. The plain is at a height varyingfrom 15,000 to 16,000 feet. A cold wind comes down ...

Ultrasound scans could soon be much more detailed, thanks to a novel material that can bend sound waves the “wrong” way. This property, known as negative refraction, means the material should bring ...