For generations, scientists studying the early universe have struggled with a shadow that lies across crucial chapters of cosmic history. Much of what we know about cosmology comes from observations of the cosmic microwave background, an all-sky afterglow of the big bang that dates to when the universe was a mere 380,000 years old and filled with incandescent plasma. But as the cosmos expanded and cooled, that primordial light ebbed and the universe faded to black, as no stars yet existed that could shine. These cosmic dark ages may have endured for as long as a hundred million years, and in that time the first stars and galaxies coalesced.
Now, however, astronomers are on the cusp of piercing this veil, using specialized radio telescopes to detect weak signals emitted by vast volumes of neutral hydrogen gas that suffused the early universe's all-encompassing darkness. The resulting maps and measurements could help address long-standing mysteries, such as the nature of dark matter and dark energy, and the manner in which the first luminous cosmic objects formed. Our top story this week, from experts Anastasia Fialkov and Avi Loeb, discusses the latest theories and observations that underpin this quest to shed light on the universe's murkiest epochs. --Lee Billings
