三年级英语作文：一次有趣的科学实验

【一】

Inancienttimes,manypeoplebelievedtheearthwasaflatdisc.Wellover2,000yearsago;theancientGreekphilosopherswereabletoputforwardtwogoodargumentsprovingthatitwasnot.Directobservationsofheavenlybodieswerethebasisofboththesearguments.First,theGreeksknewthatduringeclipsesofthemoontheearthwasbetweenthesunandthemoon,andtheysawthatduringtheseeclipses,theearth'sshadowonthemoonwasalwaysround,theyrealizedthatthiscouldbetrueonlyiftheearthwasspherical,Iftheearthwasaflatdisc,thenitsshadowduringeclipseswouldnotbeaperfectcircle;itwouldbestretchedoutintoalongellipse.ThesecondargumentwasbasedonwhattheGreekssawduringtheirtravels.TheynoticedthattheNorthStar,orPolaris,appearedlowerintheskywhentheytraveledsouth,inthemorenortherlyregions,theNorthStarappearedtothemtobemuchhigherinthesky.Bytheway,itwasalsofromthisdifferenceintheapparentpositionoftheNorthStarthattheGreeksfirstcalculatedtheapproximatedistancearoundthecircumferenceoftheearth,afigurerecordedinancientdocumentssays400.000stadium,that'sthepluraloftheworldstadium.Today,it'snotknownexactlywhatlengthonestadiumrepresents,butlet'ssayitwasabout200meters,thelengthofmanyathleticstadiums.ThiswouldmaketheGreeksestimateabouttwicethefigureacceptedtoday,averygoodestimateforthosewritingsolongbeforeeventhefirsttelescopewasinvented.

【二】

上科学课之前，老师让我们带熟鸡蛋、太空泥。我一直在纳闷，这些到底是干什么用的呢?今天谜底终于解开了。

上课了，老师让我们两人一组，每组准备一盆水，然后老师说：‘咱们要把浮在水上的东西沉下去，那沉下去的东西浮上来。“我首先把鸡蛋放入水中，发现鸡蛋是沉下去的，怎么样才能把鸡蛋浮上来呢?我的问题又来了，不一会，我把鸡蛋用手浮到水面上，一松手，鸡蛋就沉下去了。我不放弃，又想把太空泥裹在鸡蛋上会怎么样呢?我二话不说，立刻把太空泥裹在鸡蛋上，放入水中，鸡蛋就浮上来了，我的脸上露出了微笑，心里想吃了蜜一样甜。接着，我又把太空泥放入水中，太空泥是浮起来的，我想把一点重物加在太空泥里，会怎么样呢?我开始跃跃欲试，我一边做，一边嘴里说：”先加一点重物，再放入水中。“不一会儿，太空泥就沉下去了，我的实验又获得了成功。我高兴极了，科学实验真的太有趣了。