Traveling at 99.99% of the speed of light would indeed enable significant advancements in interstellar travel compared to slower speeds. At such relativistic speeds, several interesting effects come into play due to the principles of special relativity.
One key effect is time dilation. According to the theory of relativity, time slows down for objects moving relative to an observer at rest. As an object approaches the speed of light, time dilation becomes more pronounced. From the perspective of someone on board the spacecraft, time would pass slower compared to an observer at rest. This means that while a significant amount of time might pass on Earth or for observers outside the spacecraft, the travelers themselves would experience a much shorter duration. This time dilation effect would make interstellar distances more manageable from the travelers' perspective.
However, from the perspective of an outside observer, the distances to be traveled would still be vast. Even at such high speeds, the vastness of interstellar distances would still pose significant challenges. The nearest star system to our solar system, Alpha Centauri, is approximately 4.37 light-years away. Even if we were traveling at 99.99% of the speed of light, it would still take over four years (from the perspective of an observer on Earth) to reach Alpha Centauri. While this would be a tremendous improvement compared to slower speeds, interstellar travel would still require substantial time and resources.
Furthermore, there are practical considerations related to energy requirements, propulsion systems, and the safety of occupants during interstellar travel at relativistic speeds. Developing the necessary technologies to achieve such high velocities and ensuring the well-being of the crew over long durations are significant challenges that would need to be addressed.
In summary, traveling at 99.99% of the speed of light would greatly enhance the feasibility of interstellar travel compared to slower speeds. However, interstellar distances are still vast, and numerous technical, logistical, and safety challenges would need to be overcome to make practical interstellar travel a reality.