Normal, clean rain has a pH value of between 5.0 and 5.5, which is slightly acidic. However, when rain combines with sulfur dioxide or nitrogen oxides—produced from power plants and automobiles—the rain becomes much more acidic. Typical acid rain has a pH value of 4.0.
The stimuli plants respond to will be found in the environment. Example....plants grow towars the sun.
In 2016, a rare transit of Mercury happened, where the planet crossed the face of the sun. Mercury's transit may have yielded secrets about its thin atmosphere, assisted in the hunt for worlds around other stars, and helped NASA hone some of its instruments.
The thick loess deposits in South Dakota, Nebraska, and Iowa come from the glacial sediments from the last ice age glacial period.
