Even by the standards of her extraordinary life, Tuesday's visit to the Goddard Space Flight Centre in Maryland afforded the Queen with a once-in-a-lifetime experience. The monarch got the opportunity to chat with astronauts currently living in the International Space Station, on the last day of her official US tour.
Using a live video link-up, the royal matriarch talked to three astronauts - Russians Fyodor Yurchikin and Oleg Kotov, and America's Suni Williams - who described to their royal guest the experiments they are working on during their time in orbit.
While she listened with obvious fascination to plans for further expeditions to the moon and sending men to Mars, her husband had a burning question on his mind. "How do you answer the call of nature during space walks?" asked Prince Philip.
Later that day the royal pair were reunited with President George W Bush at a ceremonial dinner at the British Ambassador's residence. Addressing the assembled guests the Queen began her speech with a humorous reference to the American leader's slip-up the previous day in which he inadvertently aged her by 200 years by referring to her previous visit as taking place in 1776.
The US premier quickly realised his mistake and corrected himself, but it didn't stop the Queen from getting her own back at the event. "Mr President, I wondered whether I should start this toast saying I was here in 1776 but I don't think I will," she quipped, before going on to thank Mr Bush and his predecessors for their contribution to the Northern Ireland peace process.
Click here for a gallery of the Queen's US visit