2. "Nobody can stop it. I will keep sending leaflets into North Korea at the risk of my life," Park said, adding he has always prepared to face down the North's threats.
3. Graduates of Tsinghua University make more money, on average, than those from any other college in China, results of a recent survey showed.
4. Astronomers confirmed a key part of Einstein’s general theory of relativity in 2016 when they announced that the LIGO array had detected gravitational waves released by the collision of two black holes. The researchers won a Nobel Prize for the discovery. But they’re not done: In October, scientists announced the finding of two dead stars colliding — not only hearing the ripples in space-time they made, but confirming the event visually with powerful telescopes. Collisions of neutron stars are believed to be the source of all heavy metals in the universe, including gold and silver, and the detection by LIGO helps verify accepted explanations of how the chemistry of the universe formed.