I am sure this question is a lot more elementary than a lot of other posts on here - I am definitely a layman rather than a specialist, so I hope this isn't a problem. My hypothetical question is this: Person A is standing directly on earth, looking at his watch (so moving at the same speed relative to each other); Person B is moving close to the speed of light away from earth, again, looking at his watch. My layman's knowledge would tell me that time for Person B would slow down and take longer than Person A due to time dilation. However, if Person A was to watch a live video stream of Person B, what would he see? If 5 minutes for Person A takes 15 minutes for person B, there is a 10-minute gap, which I can't explain. Thanks in advance.