During astronomical twilight, Earth’s atmosphere can refract sunlight, scattering some skyward. But when the Sun reaches 18° below the horizon, the sky is truly dark.

Our atmosphere is a diaphanous veil; thin, fragile, transparent, and the only thing that protects us from the harsh vacuum of space. Too much atmosphere, and the planet is choked and suffocated.

An extensive and previously unknown “twilight zone” of particles in the atmosphere could complicate scientists’ efforts to determine how much the Earth's climate will warm in the future, a ...

It may not be a dimension as vast as space nor as timeless as infinity, but the ocean’s “twilight zone” is affecting Earth’s climate, due to the heavy presence of phytoplankton in the region.

The ocean helps relieve our atmosphere of a lot of the excess carbon dioxide we've pumped into it. Here's how its "twilight zone" makes that happen, and how the impacts of climate change make it ...

The Red Planet’s thin atmosphere and complete lack of light pollution would make for dark martian skies, but dust can reduce the stars’ brightness by several magnitudes.

In the backlit twilight view, sunlight filters through Pluto's many-layered atmosphere and lights up certain features, including the towering Norgay Montes mountain range and the vast plain known ...

Deep below the ocean surface, the light fades into a twilight zone where whales and fish migrate and dead algae and zooplankton rain down from above. This is the heart of the ocean's carbon pump ...