By Kip Thorne
Technically savvy scientists and engineers have put much effort into conceiving far-future technologies that might make possible near- light-speed travel. You can learn a lot about their ideas by browsing the web. It will take many centuries for humans to make any of those ideas real, I think. But they do convince me that ultra-advanced civilizations are likely to travel between the stars at a tenth the speed of light or faster.
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