If there were no atmosphere, the sky would be all black, except for the area directly around the sun, which you would not be able to look anywhere near because it would be so bright, as there would be no atmosphere to block its rays.
Contagion and contagiousness refers to how easily the spread of Genetic Disease is possible from one person to another. Other words for contagion include infection, infectiousness, transmission or transmissability. Contagiousness has nothing to do with genetics or inheriting diseases from parents.
Non-infectious diseases (also called Non-communicable diseases) are those diseases that are not caused by a pathogen and cannot be shared from one person to another. Non-infectious diseases may be caused by either the environment, nutritional deficiencies, lifestyle choices, or genetic inheritances.enetic disorders are caused by errors in genetic information that produce diseases in the affected people. These errors may include: A change in the chromosome numbers, such as Down syndrome A defect in a single gene caused by mutation, such as Cystic Fibrosis. Environmental disease is a very broad category.