Shrinking Dark Matter Makes Dark Energy

Starting about ten billion year ago, the universe began doubling in size every ten billion years or so. The driving force for the doubling is a mysterious “dark energy” that tries to hold the universe together with its bare hands. Yet in a cosmic twist, the universe uses the very tension exerted by the dark energy to fuel the exponential growth of space with time.

**Dark Energy Survey Footprint**–Starting eleven years ago, the Dark Energy Survey team spent nearly a thousand nights over six years high in the Chilean Andes at the Cerro Tololo Inter-American Observatory, shown here in the light of the Milky (above left dome) and an extragalactic next-door neighbor (above center dome), to catch the light from three hundred million galaxies that are billions of light-years from Earth within the “footprint” (above right dome) that covers almost one-eighth of the sky (Image credit: Yuanyuan Zhang),

This month Science Synergy Science Chair Noah Bray-Ali related the doubling rate of the universe to the amount of normal matter in the universe. The relation comes from the nature of the dark matter that drove the expansion of the universe for the first few billion years after the Big Bang (See Making Dark Matter in the Big Bang). As the universe expands, dark matter shrinks until one day–about 180 billion year from now–the dark matter gets so small–about one hundred million times smaller than the nucleus of the hydrogen atom–that it splits into the mirror matter and normal antimatter that joined to form it at the Big Bang.

Free for the first time in nearly 200 billion years, the quarks and leptons–both mirror and normal–along with their antiparticles, move with the speed of light at the edge of the universe. And they are lonely. Longing for the old bonds, they grow in size–and the universe shrinks–until they reach the hot dense state in which dark matter can form again and the next big bang can begin.