How much credit they would receive was questionable: they arrived in Texas at the start of the rainy season, and the amount of rainfall that occurred prior to the test had been forecast by the U.S. Weather Bureau. As for Powers’ belief that rain would fall after a battle, it was merely a natural cycle, as battles tended to begin in dry weather, and the rainy weather often continued.
Despite the scepticism of serious scientists and ridicule from some in the press, the Midland experiment ignited half a century of rain-making pseudoscience, and the Met Office soon found itself embroiled in a battle with the media to expose the efforts of would-be rain-makers who had begun operating across the country.
The most famous of these men was Charles Hatfield, nicknamed either “the moisture promoter” or “the Ponzi of the sky,” depending on who you ask. Originally a sewing-machine salesman from California, he reinvented himself as a weather expert and struck dozens of deals with beleaguered towns. Once in a new location, he built a series of wooden towers and secretly mixed 23 chemicals that had been aged in barrels, then poured them into a vat at the top of the towers to evaporate into the sky. Hatfield’s method was like magic, but he also had a knack for manipulating probability. He promised Los Angeles 18 inches of rain between mid-December and late April, even though historical rainfall records gave it a 50-50 chance anyway.
While these showmen and charlatans are lining their wallets, scientists are slowly actually The rain comes from particles called cloud condensation nuclei. Even on a sunny day, the sky is full of particles, some as small as a pollen grain or a virus strand. “All cloud particles in the Earth’s atmosphere formed on top of pre-existing aerosol particles,” one cloud physicist told me. The types of particles vary from place to place: in the UAE, they’re a complex mix of sulfate-rich sand from the empty quarter desert, salt spray from the Persian Gulf, chemicals from the oil refineries dotting the region, and organic matter from as far away as India. Without them, there would be no clouds at all, and no rain, snow, or hail.
Most raindrops start out as ice crystals in the air that melt when they hit the ground, but without cloud condensation nuclei, ice crystals wouldn’t form until temperatures dropped below minus 40 degrees Fahrenheit. As a result, the atmosphere would be filled with chunks of supercooled liquid water that’s below freezing but isn’t actually frozen.
In 1938, a German meteorologist suggested that scattering artificial cloud condensation nuclei over these frigid waters might encourage the formation of ice crystals. The ice crystals would quickly grow large and fall, first as snowflakes and then as rain. After World War II, American scientists at General Electric picked up the idea. One group, led by chemists Vincent Schaefer and Irving Langmuir, discovered that solid carbon dioxide, also known as dry ice, could do the job. When Schaefer dropped grains of dry ice into a home freezer that he was using as a makeshift cloud chamber, they found that water readily froze around the grains’ crystalline structure. Witnessing the effect a week later, Langmuir jotted down three words in his notebook: “weather control.” Within a few months, they were dropping grains of dry ice from an airplane over Mount Greylock in western Massachusetts, creating streaks of ice and snow that stretched three miles.
