Where do the stars and light itself come from? Is there a hidden sector of particles and forces called “dark energy” that affects the cosmos?
By Josh Fischman edited by Josh Fischman

Scientific American
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“Most of the matter in our universe is invisible,” write Tracy R. Slatyer and Tim MP Tait in this special edition. Slatyer is an astroparticle physicist at the Massachusetts Institute of Technology and Tait is a high-energy particle physicist at the University of California, Irvine. They have been searching for most of the universe for a long time and have not found it. “We can measure the gravitational pull of this “dark matter”” they say in this article. They can see how it bends light and how it affects the remains of the burning big bang. “We have every reason to believe that dark matter is everywhere. Yet we still don’t know what it is.”
Most of existence is therefore everywhere – and at the same time, it is nowhere. This is just one of the giant enigmas of cosmology that Scientific American explore in this collection. Where do the stars and light itself come from? Is there a hidden sector of particles and forces called “dark energy” that affects the evolution of the cosmos? Is the universe expanding at a faster or slower rate? What’s inside a black hole? And if Earth isn’t the only planet that supports life, where are the others, and what might extraterrestrial life look like, anyway?
It’s not that scientists don’t have answers to these puzzles. They do it. They have a lot of them. The big task now is to determine which one is right. Amazing instruments such as the James Webb Space Telescope (JWST) have been launched recently to solve these problems. “The observatory has begun to answer some of the biggest questions in astronomy. It also raised many new ones“, writes José María Diego Rodríguez, an astrophysicist at the Spanish National Research Council. Diego Rodríguez is particularly focused on JWST’s discovery of “supermassive” black holes dating back to the dawn of time. These beasts could be mergers of smaller black holes, themselves from explosions of so-called dinosaur stars. If astrophysicists succeed in spying on such stars, they will also have detected the first starlight, who shaped the evolution of the universe.
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And as the universe changed, life could have evolved with that— not just on Earth, but perhaps on some of the more than 6,200 other worlds identified by the Kepler space mission and similar efforts, as journalist Sarah Scoles writes. Such life could resemble microbes living under the polar ice caps of Mars; as we report herethe Perseverance rover was looking for signs on the Red Planet. Or life could exist in the buried oceans of Europaone of the moons of Jupiter, or in the geysers of Enceladus, one of the moons of Saturn.
Some aspects of space are safer and we can show them to you in eye-catching visuals. Some are the magnetic fields of other planets like Jupiter, detected by probes. In this roomwe trace the growing number of people who have gone to space, a who’s who of explorers recently joined by the crew of the exciting Artemis II mission to the far side of the moon. Astronauts have increased in number and diversity, but all still have something in common: the human desire to answer questions about everything in the universe.
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