According to the theory of relativity, time dilation occurs when an object moves at speeds close to the speed of light or experiences strong gravitational fields. As an object's velocity increases, time appears to pass slower for that object relative to a stationary observer.
The reason we cannot experience time dilation while traveling in space at near light speed is because we are always at rest relative to ourselves. From our perspective on the spaceship, time would pass normally, and we wouldn't notice any significant time dilation effects. However, observers outside the spaceship would see time passing slower for us due to our high velocity.
Time dilation is a relative effect, meaning it depends on the relative velocities of different observers. If two observers are moving at different speeds relative to each other, they will measure different rates of time passing for each other. So, while traveling at near light speed, we would observe time passing normally on our spaceship, but someone observing us from a stationary position would see our time passing slower.
It's worth noting that although time dilation is a well-established phenomenon in physics, it becomes more pronounced at speeds close to the speed of light. To reach such speeds, we would require an enormous amount of energy, and currently, we don't have the technology to achieve those velocities for manned space travel.