Why is a space between the rails of a railaway line where one piece jointsthe next?
The space is left to let the rail expand when it gets hot.
On a hot day, the metal expands and if it were not allowed to do this, the rails would bend out of shape.
This has caused railway accidents in the past.
Although solids expand much less than liquid or gases, the small increase can add up to a lot, when there are long lengths of rail.
For example, the difference in length of rail, in summer and winter, over the distance between London and Edinburgh, is about 1/4 mile.
We have to keep in our minds and not forget the expansion of metal when we build a very long metal bridge too.
So spaces are left in the places where themetal is joined.
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