For ecologists, the Covid-19 pandemic has presented a remarkable natural experiment in what can happen to wild animals when humans stay home.

Video of Ahmed el Ahmed disarming one of the gunmen has gone viral, and officials around the world have hailed his bravery.

After his son was repeatedly attacked, Rick Kuehner reached out to his suburban school, to the police and to other parents. The violence only got worse.

To mark the winter holidays — an especially popular time to break up — we asked people around the world for their most striking parting words to each other.