In a story we brought to you at noon, we discussed how Chinese meteorologists launched rockets into the air to cause precipitation and bring some relief to the intense heat in eastern China.
It's a process known as cloud seeding. Scientists still argue about whether or not it actually works. A few successful test point to increased precipitation in the regions where cloud seeding took place. Critics say it's impossible to know whether or not it would not have rained without the seeding. Many others say that even if it works, it is prohibitively inexpensive.
In theory this is how it goes:
In order for precipitation to form, water has to condense onto small particles known as condensation nuclei. These can be anything from dust particles to sea salt, but something has to be present. Most seeding experiments use silver iodide. It's molecular structure is very similar to ice.
Even with small amounts of moisture present, by giving the available water vapor something to condense upon, it is though by many that rain will be initiated in the area.
The United States began experiments on this is the 1940s, but by the 1970s its use waned significantly. It was considered to be too expensive.
The technique is currently practiced in six eastern China regions.
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