In the scenario you described, where there are two individuals in space and one is moving near the speed of light relative to the other, both individuals will observe the other's clock to be running slower. This apparent paradox is resolved by understanding that the principle of relativity applies equally to both observers, and each observer sees the other's clock as running slower from their own reference frame.
Let's consider two observers, A and B, where A is moving near the speed of light relative to B. From observer A's perspective, they are at rest, and observer B is moving at a high velocity. According to the principles of special relativity, observer A will perceive time on B's clock to be dilated or slowed down due to B's velocity.
Similarly, from observer B's perspective, they are at rest, and observer A is moving at a high velocity. Observer B will also perceive time on A's clock to be dilated or slowed down due to A's velocity.
Both observers experience time dilation relative to each other because their relative motion is symmetric. The principle of relativity states that the laws of physics should be the same for all observers in inertial (non-accelerating) reference frames. Therefore, the observed time dilation is symmetrical, and both observers will see the other's clock as running slower.
It's important to note that each observer can consider themselves at rest and attribute the time dilation to the other's motion. This situation is known as a relative time dilation, where both observers experience time moving slower relative to each other.