The ability for humans to travel from Earth and return largely depends on the technological capabilities and resources available. the farthest humans have traveled from Earth and returned is to the Moon during the Apollo missions. The Moon is approximately 384,400 kilometers (about 238,855 miles) away from Earth.
Beyond the Moon, human space missions have been limited to low-Earth orbit by the International Space Station (ISS) and other space probes that travel to various destinations in our solar system. For instance, missions to Mars have been proposed and are being planned, but they present significant challenges due to the much greater distance involved.
The distance from Earth to Mars varies depending on their positions in their orbits, but at its closest, Mars can be about 54.6 million kilometers (about 33.9 million miles) away. At its farthest, Mars can be about 401 million kilometers (about 249 million miles) from Earth. A round-trip mission to Mars would involve covering these distances and facing various challenges, such as life support, radiation exposure, psychological effects, and resource management.
Currently, the ability to travel to more distant locations in the universe, such as other star systems, is purely theoretical, as the required technologies are far beyond our current capabilities. The distances to the nearest stars are measured in light-years, with Proxima Centauri, the nearest known star to our solar system, located about 4.24 light-years away.
The concept of interstellar travel raises significant challenges and questions related to propulsion, travel time, life support systems, and many other factors. As technology advances and new scientific discoveries are made, the possibility of interstellar travel may become more feasible, but it remains a topic of speculation and theoretical exploration at this time.