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Speaking from beyond the grave, Professor Stephen Hawking has told a new generation growing up in an increasingly insular world: ‘Remember to look up at the stars and not down at your feet.’

The eminent cosmologist, who had motor neurone disease and died in March, had his final public thoughts broadcast at a special event to launch his last book, Brief Answers To The Big Questions.

Prof Hawking’s words of advice and defiance, echoing from an Imax screen at London’s Science Museum, brought tears to the eyes of his daughter Lucy.

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According to Einstein’s General Relativity, gravity travels at the speed of light. Proving it is far from simple, though: unlike light, gravity can’t simply be switched on and off, and is also extremely weak.

Over the years, various attempts have been made to measure the speed using studies of astronomical phenomena, such as the time delay of light as it passes through the huge gravitational field of Jupiter. While the results have been broadly in line with Einstein’s prediction, they’ve lacked the precision needed for compelling evidence. That’s now been provided by the celebrated detection of gravitational waves. Analysis of the signals picked up by the two giant LIGO instruments in the US has confirmed that gravity does indeed travel through space at the speed of light.

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PASADENA, Calif. (AP) — Developers testing an earthquake early warning system for the West Coast say its automated alerts are ready to be used more broadly, but not for mass public notification.

U.S. Geological Survey official Doug Given told reporters Wednesday at California Institute of Technology that the ShakeAlert system has transitioned from a production prototype to operational mode.

The system built for California, Oregon and Washington detects an earthquake is occurring and send out alerts that may give warnings of few seconds to perhaps a minute before shaking arrives at locations away from the epicenter.

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Maybe they’re not alien doppelgangers — mirror images of us.

But extraterrestrial life—should it exist—might look “eerily similar to the life we see on Earth,” says Charles Cockell, professor of astrobiology at the University of Edinburgh in Scotland.

Indeed, Cockell’s new book (The Equations of Life: How Physics Shapes Evolution, Basic Books, 352 pages) suggests a “universal biology.” Alien adaptations, significantly resembling terrestrial life—from humanoids to hummingbirds—may have emerged on billions of worlds.

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