The Light-Speed Wall: Mass Makes Reaching c Impossible and Near-Light Travel Hovers on Engineering, Not Physics
Traveling at the speed of light is impossible for any object with mass because it would require infinite energy; you can get arbitrarily close, which would produce extreme time dilation so travelers age less than those left behind. In theory, concepts like Alcubierre warp drives and wormholes exist, but they require exotic negative energy and remain beyond practical reach. Near-light-speed travel is the active frontier, with Breakthrough Starshot outlining a feasible (though engineering-heavy) path to about 0.2c for gram-scale probes rather than humans, while real interstellar journeys for larger objects remain firmly beyond our current physics and technology.