Uncounted numbers of "birdmen" have died over the centuries after leaping from tower or cliff, not realizing they could never flap homemade wings hard or fast enough to stay aloft.

在过去的几个世纪里，无数的“鸟人”丧失了生命，他们从高塔或悬崖上跳下来，却不知道他们摆动自制的翅膀时，力量和速度根本不足以维持飞行。

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You could even pledge enough money to base jump from the top of the tethered research tower, which will be held aloft by helium balloons.

ENGADGET: Liftport turns to Kickstarter for space elevator experiment (video)