Optics

Barnard 68 is often mistaken for a hole in space, but it’s actually a dense, opaque cloud of dust—for now

“Twilight rays” are but one of several viewing treats for the liminal time between day and night

Called Olbers’ paradox, the seemingly simple mystery of the sky’s darkness is something that stumped astronomers for centuries

A science photo book probes the colors we can see—and even “forbidden” colors we can’t

The rising moon looks huge on the horizon, but it’s all in your head

The famous exploding star T Coronae Borealis is due to detonate any day now, but it’s running a little late

The spin of a particle seems to detach and move without a body—a strange experimental observation that’s stirring up debate

New research harnessed the highly absorbent dye tartrazine, used as the common food coloring Yellow No. 5, to turn tissues in living mice clear—temporarily revealing organs and vessels inside the animals

Even Earth’s mightiest telescopes aren’t up to the task of imaging Apollo lunar landing sites. A lack of resolution is the biggest reason why

Reports of Earth-orbiting astronauts glimpsing the Great Wall of China and many other artificial structures are wildly exaggerated, but humanity’s planetary influence isn’t entirely invisible from afar

It’s possible to see celestial objects during the day, but it’s not always easy

Almost everything we know about the cosmos is conveyed by photons traveling across vast distances