Yun-Song Piao

1550 supernova flashes and millions of galaxies — that's the statistics of the DESI survey. This dataset allowed, for the first time, a suspicion: the repulsive dark energy has a hidden counterweight.

The universe is expanding faster and faster, like yeast dough in the kitchen. This expansion is helped by dark energy — the cosmic sugar. Ever since astronomers like Adam Riess noticed the acceleration in the late 1990s, they've been searching for the cause.

In its first moments, the Universe expanded faster than light could cross it. This process, inflation, left behind ripples — tiny density fluctuations from which galaxies later grew. The spectrum of these ripples is usually described by a number: if it is exactly 1, then all fluctuations, large and small, were equally strong.

The cosmic microwave background is a frozen portrait of the universe at the age of 380,000 years, when it first became transparent.

The cosmic microwave background is the first light that pierced the dense fog of the early universe. Its spectrum, like a frozen score of a cosmic symphony, preserves the tiniest density fluctuations from which galaxies grew.

Ever since Edwin Hubble discovered the fleeing of galaxies, the law of expansion of the Universe — Hubble's Law — has been a cornerstone of cosmology.