The Earth's orbit is very close to being a perfect circle, but not quite. It is somewhat elliptical, which means that the distance between the Earth and the Sun varies over the course of the year. This effect is too weak to cause the seasons, but it might have some influence over their severity.
@burcidi-- I don't think so. Three weeks is too long as an incubation period for a common cold. The incubation period is usually a few days in most people, but it can be up to a week. If you had said two weeks, then I would have said maybe, but I doubt that you picked up the cold from your friend.ymptoms can appear in just a few hours or as long as 10 days after exposure. The average incubation period is one to three days. Medications do not affect the incubation of a cold, nor do they eradicate it unless it is accompanied by a bacterial infection.
Top 10 facts about the world. A cold is an upper respiratory infection caused by a virus called rhinovirus. The common cold incubation period varies greatly from one person to the next. Symptoms can appear in just a few hours or as long as 10 days after exposure.The average incubation period is one to three days.Medications do not affect the incubation of a cold, nor do they eradicate it unless it is accompanied by a bacterial infection.ymptoms can appear in just a few hours or as long as 10 days after exposure. The average incubation period is one to three days. Medications do not affect the incubation of a cold, nor do they eradicate it unless it is accompanied by a bacterial infection.