[samtheman]

Looking at such distant galaxies, they found that, about 2 billion years ago, the universe was producing roughly twice as much as it is today.

---

How do we know how much light the universe is producing TODAY if the only light we can see is FROM THE PAST?

[Cboldt]

-- How do we know how much light the universe is producing TODAY if the only light we can see is FROM THE PAST? --

Extrapolation. View light from a galaxy 10 billion light-years away (estimate intensity), view light from galaxies 1 billion light-years away, extrapolate to the present.

Everything we perceive is "in the past."