The Echo That Fills the Universe

In 1964, two Bell Labs engineers in Holmdel, New Jersey — Arno Penzias and Robert Wilson — couldn't figure out why their radio antenna kept picking up a persistent, low hum. They cleaned pigeon droppings off the dish. They recalibrated every instrument. Still, the noise remained. It came from every direction, at every hour, in every season. What Penzias and Wilson had stumbled upon was the cosmic microwave background — the residual glow from the very birth of the universe.…