Why our nipples get hard when it’s cold outside

Want to read Reddit but don’t have the time? Our daily Reddit Digest highlights the most interesting or important discussions from around the social news site—every morning.

• Why our nipples get hard when it’s cold outside. (r/askscience)

• The best questions and answers from /r/askscience in 2012. (r/askscience)

• This conspicuously bad comment has been upvoted to the top of r/bestof and r/DepthHub, despite getting thoroughly trashed in r/bestof and r/DepthHub. (r/bestof)

• A map of Reddit’s “meta” ecosystem. (r/TheoryOfReddit)

• Espionage in the colonial era. (r/AskHistorians)

• The top 500 AMAs, divided by category. (r/TheoryOfReddit)

• This is pretty amazing: “IAmA 93 year old who co-wrote the original radar manual during WWII and also worked at JPL for many years on satellites.” (r/IAmA)

Pic of the day: “After a year subscribed to r/books, I suddenly realised that you might be interested to see where I work…” (r/books)
Hottest subreddit: r/bestof2012 (1 day)