Which scientist discovered that objects in water are lifted up by a force that helps them float

问题描述:

Which scientist discovered that objects in water are lifted up by a force that helps them float
这句话中的两个 that 的含义和区别

语法上,第一个是宾语从句的关联词,第二个是定语从句中的关联词.
意义上,第一个无实义,就是分开主句和宾语从句,表示“discover”的内容.第二个that引导的定语从句修饰"a force",相当于“the force”.