Albert Einstein’s theory of gravitational redshift was proven after a telescope in Chile observed a black hole.
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President Harry Truman signed the National Security Act.
In one day, Facebook lost $120 billion in value on the stock market.
The opera 'Parsifal' by Richard Wagner premiered in Bayreuth, Germany.
President Donald Trump banned transgender persons from joining the US military.
The Summer Olympic Games opening ceremony was held outdoors for the first time ever.
