The core reasons usually are
- Distance is staggering — even our fastest spacecraft would take thousands of years to reach the nearest star.
- No known propulsion gets us close to light speed; physics doesn’t currently allow practical faster-than-light travel.
- Energy requirements for interstellar travel are far beyond what we can generate or carry.
- Human survival over such long journeys (radiation, life support, generations aboard a ship) is an unsolved problem.
Net effect: with known physics and current technology, leaving the solar system is more theoretical than achievable — though this isn’t a hard proof, just where science currently stands.
