Cosmology and astrophysics: the age, shape and contents of the universe, and the arguments over how we measure them.
5 stories. Section line: Doubly ionized oxygen, 500.7 nm.
A light year is a distance, not a time. We worked out how long it would take to travel one by train, by plane and by spacecraft, and how far India’s own missions are in light-time.
The number comes from running the expansion of space backwards. We did that calculation ourselves, then checked it against the oldest stars, a clock that no expansion measurement can touch.
Measure the expansion rate from the early universe and you get one number. Measure it from nearby galaxies and you get another. A decade of better data has made the gap harder to explain away.
The cosmic microwave background was released when the universe was 380,000 years old. Its faint ripples encode the universe’s age, contents and shape. Here is how to read them.
The largest three-dimensional map of the universe hints that the force driving cosmic acceleration may be weakening. A 2026 reanalysis has made that evidence weaker, and more interesting.