n More on non-stop flight records: The world’s longest-distance non-stop passenger flight was 13,422 miles, from Hong Kong to Heathrow (eastbound) by a Boeing 777 in 2005, taking 22 hours and 40 minutes. Surprisingly, the record for the longest-time non-stop passenger flight was set way back in 1957, when an old Lockheed Starliner propeller plane took 23 hours, 19 minutes to get from London to San Francisco.

The most common naturally occurring isotope of the element uranium is U-238. In the process of its radioactive decay, U-238 is transformed into a succession of elements, the final, atomically stable one being:

A) Gold

B) Nickel

C) Silver

D) Hydrogen

Tuesday’s answer: Leonardo da Vinci painted his “Mona Lisa” on a poplar panel.

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