Best of: The future of the universe

In this rerun of a standout episode from The Future of Everything, host Russ Altman interviews astrophysicist Professor Risa Wexler from Stanford University about the evolving understanding of the universe, galaxy formation, and the mysterious forces of dark matter and dark energy. Wexler explains how cutting-edge tools like the Rubin Observatory’s Legacy Survey of Space and Time—featuring a 3.2-gigapixel camera—will enable unprecedented 2D and 3D mapping of the cosmos. She emphasizes that light travel time allows us to look back in time, revealing the universe’s evolution from its hot, dense beginnings 13.8 billion years ago. The discussion delves into the structure of the universe: not centered or edged, but vast and uniform on large scales, yet clumpy on smaller ones due to early quantum fluctuations. Wexler highlights how dark matter—though invisible and non-interacting—shapes galaxy formation through gravity, while dark energy drives the universe’s accelerating expansion. A major focus is her team’s ambitious survey identifying 400 satellite galaxies around 101 Milky Way-like systems, offering a comparative framework to understand our own galaxy’s history, including a recent collision with the Large Magellanic Cloud. The episode closes with a call for audience engagement and exploration of the podcast’s extensive archive. Key takeaways include: 1) The universe is not centered or edged—our observable universe is a sphere of 13.8 billion light years in radius, but the full universe may be infinite; 2) Dark matter, though undetected directly, governs galaxy formation through gravity and is everywhere, even passing through us; 3) Dark energy is responsible for the universe’s accelerating expansion, a phenomenon confirmed by large-scale maps; 4) Studying satellite galaxies around Milky Way analogs helps contextualize our own galaxy’s formation history; 5) The combination of imaging and spectroscopy (measuring redshift) allows astronomers to build 3D cosmic maps; 6) The James Webb Space Telescope has revealed galaxies forming just a few hundred million years after the Big Bang; 7) Future experiments, including underground detectors, aim to directly detect dark matter particles; 8) Understanding galaxy diversity requires studying them in context, much like clinical trials in medicine.