Communicating with a relativistic spacecraft gets pretty weird

Someday, in the not-too-distant future, humans may send robotic probes to explore nearby star systems. These robot explorers will likely take the form of lightsails and wafercraft (a la Breakthrough Starshot) that will rely ...

The big emitters: the United States

The United States, the world's second largest emitter of greenhouse gases, has pledged to halve its emissions by 2030 compared to 2005 levels—but so far is failing to stay on target, analysts say.

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