Kent Hups, a high school science teacher in Colorado, discovered a 23-foot trackway of fossilized dinosaur footprints, which offer a glimpse of how the apex predator moved 66 million years ago.

Joan Birman thought her major discoveries were behind her. Then came an email from a young neighbor — a girl who knew little but wanted to learn.

© Oliver Farshi for The New York Times

Meet the earliest known insects. Shaking hands with them will take a while.

Given access to email, A.I. agents have started reaching out to the philosophers and researchers exploring deep questions about them.

© Benjamin Rasmussen for The New York Times