An image from a simulation of two black holes merging. Courtesy of SXS Collaboration hide caption

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The Philae lander, seen here heading to a comet's surface after leaving the Rosetta spacecraft in 2014, isn't expected to send any more signals, the European Space Agency says. ESA/Rosetta/MPS for OSIRIS Team hide caption

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The Smithsonian is sharing images of astronaut graffiti aboard the Apollo 11 command module, including this tribute to the spacecraft. Smithsonian Air and Space Museum hide caption

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"We are very different from all previous species, and we have the power to endure. We also have the power to destroy ourselves." — Lord Martin Rees Ryan Lash/TED hide caption

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TED Radio Hour

Lord Martin Rees: How Can We Ensure Our Survival As A Species?

Astronomer and cosmologist Lord Martin Rees asks whether our species will endure despite the many existential threats we face.

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A simulation shows gravitational waves coming from two black holes as they spiral in together. S. Ossokine , A. Buonanno (MPI for Gravitational Physics)/W. Benger (Airborne Hydro Mapping GmbH) hide caption

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NASA Administrator Charles Bolden speaks at a panel discussion on the search for life beyond Earth at NASA headquarters in 2014. Joel Kowsky/NASA hide caption

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Luxembourg City, the capital of Luxembourg — shown here in 2012 — mixes the medieval and the modern. The tiny European nation is making a serious bid for the futuristic, too. Loop Images/UIG via Getty Images hide caption

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(Left) Bob Ebeling in his home in Brigham City, Utah. (Right) The Challenger lifts off on Jan. 28, 1986, from a launchpad at Kennedy Space Center, 73 seconds before an explosion killed its crew of seven. (Left) Howard Berkes/NPR; (Right) Bob Pearson/AFP/Getty Images hide caption

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