According to our current understanding of physics, time dilation occurs as an object approaches the speed of light. Time dilation means that time appears to pass more slowly for an object in motion relative to an observer at rest. As an object's velocity increases towards the speed of light, time dilation becomes more pronounced.
At the speed of light itself, time dilation is believed to be infinite, meaning time does not progress for the object traveling at that speed. However, it's important to note that, based on our current knowledge, massive objects with mass cannot attain or exceed the speed of light.
If we consider the concept of hypothetical "interstellar travel" at speeds approaching the speed of light, time dilation would indeed occur. From the perspective of an observer on Earth, time would appear to pass more slowly for a spacecraft traveling at such speeds. This would mean that while the travelers aboard the spacecraft might experience a shorter duration for their journey, time would continue to pass as usual for them. In other words, they would still age during their voyage, though less time would have elapsed for them compared to an observer on Earth.
It's important to remember that this explanation is based on our current scientific understanding, which is subject to further research and refinement.