Stephen Hawking, in his own words

In memory of Stephen Hawking, who died on Wednesday at 76, the New York Times has gathered a selection of his quotes:

“Remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist. Be curious. And however difficult life may seem, there is always something you can do and succeed at.”

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First glimpses of the cosmic dawn

Marina Koren reports:

Near the beginning, not long after the Big Bang, the universe was a cold and dark place swirling with invisible gas, mostly hydrogen and helium. Over millions of years, gravity pulled some of this primordial gas into pockets. The pockets eventually became so dense they collapsed under their own weight and ignited, flooding the darkness with ultraviolet radiation. These were the very first stars in the universe, flashing into existence like popcorn kernels unfurling in the hot oil of an empty pan.

Everything flowed from this cosmic dawn. The first stars illuminated the universe, collapsed into the black holes that keep galaxies together, and produced the heavy elements that would make planets and moons and the human beings that evolved to gaze upon it all.

This epoch in our cosmic history has long fascinated scientists. They hoped that someday, using technology that was calibrated just right, they could detect faint signals from that moment. Now, they think they’ve done it.

Astronomers said Wednesday they have found, for the first time, evidence of the earliest stars. Using a table-sized radio instrument in the desert in Western Australia, the researchers detected radio emissions from the cold hydrogen that interacted with brand-new stars in that stage of the early universe.

Astronomers from Arizona State University, MIT, and the University of Colorado at Boulder, funded by the National Science Foundation, spent more than a decade trying to find this signal, calibrating and recalibrating the technology. Their results were published in Nature. [Continue reading…]


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