Henry Segerman is a mathematician who likes to make clever, remarkable mathematical shapes and 3D print them out into real things. He then makes a youtube explaining their origins. Each beautiful object becomes a mathematical lesson. He favors odd gears, weird knots, unusual shapes. You can watch Segerman videos for very nerdy satisfaction, but to fully close the loop, you can also purchase one of his exquisite objects shown in the videos. I have a few on my shelf. They are both conversation pieces and mathematical proofs, and great gifts for the nerds in your life. — KK.

The Voyager Golden Record, included on the 1977 Voyager space missions, is a collection of Earth's sounds, music, and images intended as a message for extraterrestrial intelligence. My friend David Pescovitz won a Grammy for the Voyager Golden Record 3xLP Box Set he co-produced, which includes the original content and an illustrated book. Normally priced at $110, it is currently on sale for $88. — MF