OriginsAnswer
How old is the universe, and how do we know?
About 13.8 billion years, read from the oldest light in the sky and checked against the oldest stars, with one real puzzle still open about how fast space is stretching today.
TOPIC
Cosmic microwave background.
Stories and answers about #Cosmic microwave background
FROM THE QUESTION LIBRARY
Short answers, with sources.
OriginsExplainer
Can a Telescope See the Beginning of the Universe?
Distant light lets us look far into the past. But the earliest light we can receive arrived after the universe had already been changing for a long time.