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Entrancing Vortices
A vortex is a rapidly whirling spiral, a body of fluid or gas rotating around its own centre.We see vortices around us all the time: water going down the plug hole, tornadoes and hurricanes are all good examples.
When trying to explain what causes these fascinating effects to occur, it is best to look at an environment where they appear and consider what is going on.
Let’s look at water swirling down a plug hole, like in the picture above: When the stopper is removed, the force of gravity pulls the water down the plug hole. But, at the same time, the air in the pipes below is pushing upwards, trying to escape. This ‘battle at the plug hole’ means that neither air nor water flow easily until a vortex is formed. This is the best way for the water to travel down the plug hole because it means that the spiralling water can travel down the plug hole whilst air can travel out through the central tube.
In this fascinating picture, coloured smoke is used to show the vortex formed in the air when a jet takes off. When air or liquid rushes in to an area of low pressure, it forms a vortex. All the ‘stuff’ falling inwards has so much speed that it can’t just come to a sudden halt, so spirals inwards instead!
Vortices are also found in space. Matter spirals inwards to form huge galaxies, much like our own, the Milky Way!
Some good web links to try:Exploratorium-Vortices
