110- Another Example
You measure a room. Then, some of its plasters fall or stick to someone's coat, and consequently, the room's length increases. Alternatively, humidity may grow into the walls and decrease the length. Now, the dimensions of your room are different. Even if this variation is minimal, it still is a change in dimension.
A five-meter-long I-beam girder in summer is approximately half to one centimeter longer than that same girder in winter. With this scale, its size constantly changes with changes in the weather.
In short, no object can ever maintain its actual state1 .
The I-beam girders in large iron bridges are placed farther than the required distance to compensate for the summertime expansion to avoid destruction.
Besides, constructors usually put a one to two centimeters gap between girders on railways to avoid pressure onto each other when they expand. However, we have seen that during scorching seasons, rails expand excessively and get warped and lose their proper placement.
Footnotes
- Wood expands in the winter due to moisture and shrinks in the summer when the weather is dry. On the contrary, iron shrinks in the winter due to coldness and expands in the summer. Therefore, if an iron girder is measured with a wooden meter during winter and summer, a significant difference in measurement becomes more evident. Another example is cutting a piece of wood and a piece of iron of the same size. Then set them beside one another. According to this principle, you will see that their size will not remain the same in the summer and the winter, even though they were initially the same size.