THE EARTH SPINNING ON ITS AXIS CAUSES THE DAY/NIGHT CYCLE
The fast spin (1 turn every 24 hours) of the earth keeps its temperatures moderate over a large portion of the planet. In general, the amount of light hitting the surface of any one area of the earth, determines the temperature there. This holds if we are talking about the year-long cycle of the seasons, or in the 24 hour day/night cycle.
Its worth noting how quickly temperatures can change. In the course of 24 hours, just 12 hours of light/darkness can normally raise/lower a temperature 10 to 40 degrees F. If the earth were spinning slower, creating a longer day/night cycle,those changes would become greater. Imagine how hot a July day be if the sun were up for 50 hours, or how cold a January night would be in a 50 hour night.
As evidenced by Mercury, it is not so much how far you are from the sun, but how long you are exposed, and what substances around you retain heat. Of these two, the length of exposure is the much more important. If the earth were to stop spinning (and not fly apart) it would be hours, not more than a day or two, before the side towards the sun burned up while the dark side froze. Additionally, the temperature disparities created in such a scenario would create massive super storms, mega-canes created by the heat, blizzards by the cold, and very violent manifestations where these systems met each other.
COMPLEX INTELLIGENCE THROUGH COMPLEX ENVIRONMENT