About:

I will try to collect here a few of the better, less-known, riddles and paradoxes: ones that are easy to understand but hard to solve.
There are also links to a few interesting articles and other things.

My works could be found on my academic site.

Riddles

• Which of the following organisms is the closest to Homo sapiens (evolutionary):
  Fly / Nematode / Crab / Starfish ?
• What is the function of this instrument?
  
• The moon is a harsh mistress [link]
• Exchange of thoughts [link]
• The prophet of coins (very hard) [link]
• Most surprising IPhO question (IPhO 1989 Question No. 1) [link]

Physical paradoxes

• The rope paradox (hard) [link]
• The train paradox (hard) [link]
• The Poynting-capacitor paradox (very hard / O E's) [link]

Interesting papers and links

• What Problems to Solve - By Richard Feynman [link]
• Einstein’s Unknown Insight and the Problem of Quantizing Chaos
  A simple introduction to the correspondence between quantum chaology and classical chaos. [link]
• The Science of Concert Hall Acoustics
  The science of building "anti-stealth" concert halls. [link]
  (possibly related to the image below)
  
• Paradoxes of the Aharonov-Bohm and the Aharonov-Casher effects
  L. Vaidman's suggestion of local mechanisms for the Aharonov-Bohm Phase. [link]
• A microscopic derivation of the quantum measurement postulates
  V. Lysov & Y. Neiman review the field of "quantum foundations". [link]
• Miscellaneous:
  Coded aperture / Coded Mask
  Pythagorean cup
  The Golden Ratio (why it is so irrational)
  

Literature:

• Shooting an Elephant / George Orwell [link]
• אלוף בצלות ואלוף שום / חיים נחמן ביאליק [link]

Other sites:

• Israeli Physics Olympiad
  The best place to learn physics in Israel for high school students (Hebrew). [link]
• APhO 12 (Tel Aviv, 2011)
  Very nice questions of the 12th Asian Physics Olympiad. [link]
• Prof. Yacov Kantor's Riddles [link]
• Israeli Tournament of Towns
  In my opinion, the most interesting math competition in Israel (Hebrew). [link]