During the day time, when the heat radiation from the sun comes towards the earth, they are reflected back into space by the earth’s atmosphere. As a result, only some amount of heat radiation is able to reach the earth. During the night, the earth radiates heat which is reflected back to the surface by the atmosphere. It is therefore, if there were no atmosphere, all of the heat radiation from the sun would reach Earth and the Earth would be inhospitably hot in the day time. On the other hand, all of the heat radiated by the earth in the night time would escape into the space thus leaving the earth inhospitably cold.
Anomalous expansion of water
Unlike other liquids, water shows unusual expansion which is called anomalous expansion of water. When temperature of water decreases from 100 C, volume of the water also decreases and hence the density increases. The volume of water becomes minimum at 4 C. If the temperature is further reduced to zero, the volume of water again expands. In further cooling from 0 C, ice contracts normally. Thus the water has maximum density at 4 C.
Small space is left between two rails on a railway track
The rail may be heated due to (i) the high temperature on summer and (ii) the heat caused by the friction between the wheels and the track. Due to these heating, the rails get expanded and enough space is to be left for the expansion of the rails, otherwise the railway track may be curved during expansion and may be displaced from the original track. Hence, the spaces are left between the rails of a railway track.
Mercury is used as a thermometric substance
Mercury has uniform expansion and it does not wet the glass tube. Therefore, mercury is mostly used as the thermometric substance.