They close up their leathery leaves to form an insulating blanket that shields their vulnerable central bud.

它们合起革质叶片形成一道保温层以保护中心脆弱的蓓蕾。

Scientists have known for centuries that a layer of gases naturally surrounds the earth like an insulating blanket, trapping the reflected energy of the sun and preventing it from escaping into space.

几个世纪以来，科学家们就已经知道气体就像绝缘毯一样自然地覆盖着地球，吸收太阳反射的能量，防止其流向太空。