一篇短问有3个地方不理解

When my interest shifted from space to the sea, I never expected it would cause such confusion among my friends. Yet, I can understand their feelings. As I have been writing and talking about space flight for the best part of 20 years, a sudden switch of interest to the depth of the sea doer seem peculiar. To explain, I’d like to share my reasons behind this unusual change of mind. The first excuse I give is an economic one. Underwater exploration is so much cheaper than space flight. The first round-trip ticket to the moon is going to cost at least 10 billion dollars if you include research and development. By the end of this century, the cost will be down to a few million. On the other hand, the diving suit and a set of basic tools needed for skin-diving can be bought for 20 dollars. My second argument is more philosophical. The ocean, surprisingly enough, has many things in common with space. In their different ways, both sea and space are equally hostile. If we wish to survive in e

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