Lift is a problem in the rarefied air of the stratosphere , and it seems such a design can help .
因为在稀薄的同温层中升力的产生是一个问题,所以这种飞行器的设计可以起到一定帮助。
Thus far , dr penrose 's version of cosmology more or less matches the standard version . At this point , though , he introduces quite a large kludge of his own . This is the idea that when the universe becomes very old and rarefied , the particles within it lose their mass .