Screwsareamazingmachines.Weusethemtoholdthingstogether,digholesbigandsmall,andsavespace.Butthesesimplemachinesdoanotherveryimportantjob.Theymove things.

Thinkaboutthedrillbitspinningintothewood.Asthebitdrillsthehole,woodshavingsandsawdustcomeoutofthehole.Thesearethetinypiecesofwoodthatthebitremoves.It’slikediggingaholewithashovelandtossingthesoilaroundtheopening.Buthowdoesascrew,likeadrillbit,movethingsthis way?

Asthedrillbitturnsandcarvesoutthewood,thegroovesbetweenthethreadscarrytheremovedpiecesofwoodupalongthe bit.

Thisideathatascrewcouldbeusedtomovethingsledtoanimportantinventionmorethan2,000yearsago.AmathematicianfromancientGreecefiguredouthowtouseascrewtoliftwaterfromarivertoirrigatecrops.HisnamewasArchimedes(sounds like ahr‑kuh-MEE-deez), andtheinventioniscalledanArchimedes’screw.Here’showit worked:

Alargescrewwasfittedinsideatube.Oneendofthetubewasplacedinariver.Aworkerturnedacrankattheotherend.Theturningthreadsofthescrewpushedthewaterupthetubeanddumpeditoutattheotherend.Fromthere,itflowedalongditchestofields.Archimedes’inventionisstillusedtoday.Ascrewisasimplemachine,butourusesforitareanythingbut simple!