Shun-Sheng Li

Light from distant galaxies passes through warped space before reaching our telescopes. Massive clumps of matter act like uneven glass: galaxy images get slightly stretched and rotated. This phenomenon is called weak gravitational lensing.

The optical sky background is a cosmic palimpsest, where light from billions of unresolved galaxies is layered, each layer corresponding to a different epoch. Until now we could only distinguish the brightest "letters"—individual stars and nearby galaxies.