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.
A answered. An infectious disease is a disease caused by a microorganism and therefore potentially infinitely transferable to new individuals. It may or may not be communicable. An example of a non-communicable disease is disease caused by toxins from food poisoning or infection caused by toxins in the environment, such as tetanus. A communicable disease on the other hand is an infectious disease that is contagious and which can be transmitted from one source to another by infectious bacteria or viral organisms. The presence of the CDC logo and CDC content on this page should not be construed to imply endorsement by the US Government of any commercial products or services, or to replace the advice of a medical professional.