Astronomers see billions of light years across the universe, b | Science & Technology

Astronomers see billions of light years across the universe, but it wasn’t always this way. Under a billion years after the Big Bang, the cosmos was “foggy“. Opaque hydrogen gas filled the early universe and this gas absorbed starlight. But the first generation of stars went to work clearing this fog away with their fierce ultraviolet light making it transparent, in a time called the era of re-ionisation