12 reasons not to get a PhD. (CBS Moneywatch) COMMENTARY Earning a doctorate is widely considered to be an excellent way to boost a person's lifetime earnings potential. 1. A PhD takes twice as long as a bachelor's degree to complete.
Most of the remaining ozone occurs in the troposphere, the layer of the atmosphere that extends from Earthâs surface up to the stratosphere. Near-surface ozone often results from interactions between certain pollutants (such as nitrogen oxides and volatile organic compounds), strong sunlight, and hot weather.
The thermosphere is the layer of Earth's atmosphere that still contains substantial molecules of heavier gases. It occurs below the outermost layer, the exosphere, which consists mainly of a near-vacuum of hydrogen and helium.