During the 20th century, there was an increasing interest in the environment. The impact of human activity on the environment has been observed locally since centuries. Pollution of canals and chimneys in crowded urban areas etc were all causes of concern.
However, with a better understanding of our earth and increase in Medical knowledge of the 20th century, we could observe how our activities were having a global impact on the ozone layer and the melting ice caps.
Evidence was also provided on how human health was affected by this. The use of fossil fuels was not only directly damaging to the atmosphere, it was also dangerous for humans e.g. carbon monoxide produced by car emissions.
As the rocky matter is refractory as it forms in the relatively high and warm and the presence of the gravity also plays a crucial role in the formation of the rocky masses.
The volatile matter solidifies at a cold temperature and such as those in the outer parts of the nebula and thus gas giant is cold and icy plants as they form away from the sun and have distinct gravitational compositions.
