beat the air

我们都知道“打”是件不应该做的事，但生活中总是会出现许多“打”的场合。大人打小孩是出于恨铁不成钢的爱子之心：人打动物是为了迫使它就范从命；人与人之间的斗争，或是为了报复，或是为了泄愤。但被打的人或动物，都是有血有肉，有感觉的肌体。否则你打他，他却不感到痛，岂不是白打了？beat the air正是这种“白打、白费劲”的意思。任你打得再凶狠，空气是不会感到痛的，不过是白费了你自己力气的徒劳之举而已：

His speech merely beat the air as his argument was not convincing at all.
他的演说一点用也没有，因为他的观点不令人信服。

He is as stubborn as a mule. All those who have tried to persuade him have only been beating the air.
他固执得很，所有试图劝说他的人都在白费口舌。

After searching for the criminal in the thick jungle for three whole days, the police had to admit that they had been beating the air.
在浓密的丛林中搜索了整整三天后，警方不得不承认，他们的力气白费了。

hide / bury one’s head in the sand

一看到这个成语，你马上就会想到鸵鸟或者人们常说的鸵鸟政策吧！不错hide / bury one’s head in the sand 是鸵鸟的一个习惯动作。鸵鸟爱把头埋在沙堆里，这样，它就可以无视周围发生的一切了。不仅是鸵鸟，有些人有时也会这样做。他们这样做是为了自欺欺人，拒绝承认他们不想接受的客观现实。自然，这是一种不明智的做法：

If you continue to hide your head in the sand and refuse to recognize the fact that some of your classmates are catching up with you, it won’t be long before you find yourself lagging behind.
如果你再拒绝承认你的一些同班同学已经赶上来了这一事实，那么不用多久，你就会发现自己落后了。

It’s unwise and even dangerous for a government to bury its head in the sand and cling to the ideal that everything in the country remains unchanged and there is no need for any adjustment in its policies.
一个政府无视现实，死守着国情不会变改，政策无需调整的理想，是不明智的，甚至是危险的。