gravity

A spacecraft built to explore icy moons where life could exist is flying close by Earth, using the planet's gravity to adjust its course. The maneuver is part of a long journey toward the outer solar system, where scientists hope to study oceans beneath the moons' surfaces. The flyby has drawn attention as a milestone in the search for conditions suitable for life beyond our planet.

A Quanta Magazine article explaining the holographic principle in physics is being discussed on Hacker News. The idea is that gravity in a volume of space can be described by information encoded on that volume's boundary, as in the AdS/CFT correspondence, suggesting three-dimensional reality may emerge from lower-dimensional information. Commenters on the post are debating what this implies about the fundamental nature of space, time and whether reality is a projection.

Physicists report new evidence that gravity can collapse the dimensions of space, supporting the idea that gravity is holographic — that the universe's three-dimensional structure may be encoded on a lower-dimensional surface. Researchers stress the implications are not yet understood, and what this means for the nature of reality remains an open question driving discussion among cosmologists and science commentators.