ANSWERS

1. The Easter Rising. Their headquarters was the General Post Office (GPO), and Patrick Pearse read the Proclamation.

2. The Library of Congress. It was restocked with Thomas Jefferson's books.

3. The Hubble Space Telescope

Hubble was launched on 24 April 1990 and released from the shuttle into orbit the next day, 25 April.

4. The Boston News-Letter

5. Troy

This is a calculation by Eratosthenes, based on traditional chronology. Historians don't know whether the Trojan War really happened, let alone the exact date.

6. The Battle of Mühlberg. The portrait was painted by Titian.

7. The Woolworth Building

8. Soyuz 1

9. "The East Is Red"

10. Benedict XVI

11. Anthony Trollope introduced the pillar box (post box).

12. Shirley MacLaine

13. Barbra Streisand

14. Sachin Tendulkar

15. Kelly Clarkson

16. Edmund Cartwright

17. Willem de Kooning

18. Daniel Defoe

19. Wallis Simpson

20. The Order of the Garter