FRITZ HABER -- a Nobel laureate in chemistry, a friend of Albert Einstein, a German Jew and World War I hero -- may be the most important scientist you have never heard of. The Haber-Bosch process, which he invented at the turn of the twentieth century, revolutionized agriculture by converting nitrogen to fertilizer in quantities massive enough to feed the world. The invention has become an essential pillar for life on earth; some two billion people...