How to Measure All the Starlight in the Universe
Astrophysicists have devised a clever way to count up the photons in space, stretching back to the cosmos’ adolescence.
Until the 20th century, astronomers were that seems as if it should have an easy answer: Why is the night sky dark? If the infinite universe has an infinite numbers of stars, as they assumed, our evening view should be awash in their glow. Astronomers eventually got the answer to this question, known as Olbers’ paradox, when they worked out that the universe doesn’t go on forever. Our finite universe, even with its trillions and trillions of stars, the night sky with light. On top of that, the universe is rapidly expanding—in fact, has been expanding since it first emerged—and stars were zooming away
