[00:02] train tracks used to have gaps in tracks expand and contract with temperature. And wheels hitting those gaps made that the tuck the tuck the tuck sound. But those gaps also slowed
[00:15] the trains down. So, today's tracks are welded into one seamless rail. No more clickety-clack. But now with expanding hot rail has nowhere to go. And if left alone, the internal pressure would build until finally the rails would violently
[00:29] buckle into the zigzag. And that is where those jagged [music] rocks come in. The tracks are attached to these sleepers and then embedded in those [music] rocks. And their jaggedness makes them physically interlock, which
[00:41] creates a huge amount of friction. So, when the steel rails expand and [music] push on the sleepers, the jagged rocks lock together and hold everything firmly in place. That keeps the rail straight even under huge internal pressure. But
[00:54] if the rocks were smooth and round, then vibrations from passing trains would make them slide around and the [music] track could quickly buckle. Subscribe track could quickly buckle. Subscribe for more.