Telescopes are time machines. Light that leaves objects takes time to travel, and the vast distances it must cross to reach us from the farthest parts of the universe means that we see the most distant galaxies as they were in their youth. That light is stretched into infrared wavelengths by the expanding universe as it travels through space, making it visible only to infrared-detecting telescopes — like Webb.
Webb will capture this long-traveling light to see the universe's infancy, the first stars and galaxies flickering to life after the Big Bang. It will study why galaxies produced stars so much faster in the past, at a rate 10 times higher 10 billion years ago. We're accustomed to seeing stately spiral and shining elliptical galaxies, but how did groups of stars evolve into these familiar shapes? Webb will uncover whether the process is something internal to galaxies or affected by outside events, such as galaxy collisions.
Shortly after the Big Bang, the universe went through a period called the Dark Ages, when no light sources were available to illuminate a cosmic darkness. Webb will look for the bright objects that transformed this dim universe to the one we see today, ablaze with the glow of stars and galaxies.