Screwsareamazingmachines.Weusethemtoholdthingstogether.Theyalsodigholesbigandsmall,andtheysavespace.Buttheydoanotherimportantjob.Screwscanmove things.

Thinkaboutthedrillbitspinningintothewood.Asthebitdrillsthehole,woodshavingscomeoutofthehole.Thegroovesbetweenthethreadscarrythepiecesofwoodupalongthe bit.

Thisidealedtoanimportantinventionmorethan2,000yearsago.InancientGreece,amathematiciancalledArchimedesfiguredouthowtouseascrewtoliftwaterfromarivertoirrigate crops.

Here’showitworked:Alargescrewwasfittedinsideatube.Oneendofthetubewasplacedinariver.Aworkerturnedacrankattheotherend.Theturningthreadsofthescrewpushedthewaterupthetubeanddumpeditoutattheotherend.Itthenflowedalongditchesto fields.

Archimedes’screw,namedafteritsinventor,hasstoodthetestoftime.Westilluseittoday!Ascrewisasimplemachine,butourusesforitareanythingbut simple!