Traveling to another galaxy at a significant fraction of the speed of light would indeed enable a spacecraft to cover vast cosmic distances within a human lifetime. However, due to the enormous scale of galaxies and the limitations imposed by the laws of physics, intergalactic travel would still require a considerable amount of time.
Let's consider some factors that contribute to this apparent contradiction:
Vast distances: Galaxies are typically millions or billions of light-years away from each other. Even at a fraction of the speed of light, the time required to traverse such distances would be significant.
Time dilation: As an object approaches the speed of light, time dilation occurs according to Einstein's theory of relativity. This means that time passes more slowly for the moving object relative to a stationary observer. However, even with time dilation, the journey would still take a considerable amount of time from the perspective of someone on the spacecraft.
Human lifespan: Human lifespans are relatively short compared to the timescales involved in intergalactic travel. Even if the journey takes several decades or centuries according to Earth-based observers, it would still span multiple human generations. Therefore, it could be described as taking a "lifetime" to reach the destination.
Technological challenges: Achieving intergalactic travel is currently far beyond our technological capabilities. The energy requirements, engineering challenges, and resource limitations make such endeavors highly speculative and theoretical at present.
In summary, while traveling at a fraction of the speed of light could significantly reduce the time required to reach another galaxy, the vast distances, time dilation, and human lifespan limitations would still make it a journey spanning multiple lifetimes. Interstellar and intergalactic travel remain subjects of scientific inquiry and exploration, with many challenges to overcome before they become feasible realities.