A.The temperature inside clouds depends on the height of the cloud and can range from 15C to -57C. The higher the cloud, the colder the core temperature.
A.Vapour trails from the rear of an aircraft are the result of jet engines injecting hot exhaust water vapour into the cold air. Not all planes do this.
Q.Why is the sky blue
A.Rayleigh scattering makes the sky blue. The blue part of sunlight has a short wavelength, so it hits air molecules, scatters off them, & you see it more.
Q.What is fog
A.Fog is a cloud in contact with the ground. It occurs when moisture from the earth's surface evaporates. Visibility of less than 1km is defined as fog.