Over those distances, even a sharp laser beam would spread to thousands of kilometres wide by the time it reached Earth.
在这种距离下,即便是聚焦良好的光束到达地球时也会分散到上千公里宽的面积上。
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By contrast, Voyager 1, the most distant functioning space probe, is using an extremely weak transmitter to beam radio messages back to earth across 10 billion miles of space.