Time dilation is indeed a real phenomenon predicted by Einstein's theory of relativity. It states that time can pass differently for objects that are moving relative to each other or experiencing different gravitational forces.
When it comes to interstellar travel, the effects of time dilation become significant when traveling at speeds close to the speed of light. As an object approaches the speed of light, time dilation causes time to slow down for the moving object relative to a stationary observer. This means that for a traveler moving at high speeds, less time would pass for them compared to the time experienced by those on Earth.
However, even with time dilation, the challenge of interstellar travel remains substantial. The distances between stars are incredibly vast, and it would take a considerable amount of time to travel to even the closest star systems. For example, the nearest star to our solar system, Proxima Centauri, is about 4.24 light-years away. If a spacecraft were to travel at a significant fraction of the speed of light, it could potentially reach Proxima Centauri in a matter of years from its perspective due to time dilation.
Returning home, though, presents a greater challenge. The time dilation effect works both ways, meaning that while time may pass more slowly for the traveler, it would still pass normally for the people on Earth. So, even if the travelers experienced only a few years of subjective time, decades or even centuries could pass on Earth.
This means that any extraterrestrial travelers who journeyed to Earth from a distant star system would likely face the dilemma of returning to a vastly changed world or finding their home civilization potentially long gone. Overcoming these challenges would require advanced technology, such as faster-than-light travel or the ability to hibernate for extended periods.
It's important to note that while time dilation is a well-established concept in physics, the practical realization of interstellar travel and the associated challenges are still largely theoretical at this point.