Good day, I'm a high schooler so my knowledge of physics is futile and still expanding. Please correct me when I'm wrong, I love physics. Now to my question. I'm still a bit fuzzy on this theory of time dilation and the speed of light etc. But if time dilation happens at the speed of light can it also happen at slower speeds such as the speed of sound? If this is true does the amount of time dilation change within a different medium or a vacuum all together? My understanding of time dilation is that if you (or an object) that is traveling at the speed of light moves or emits a beam of light then that beam/movement will still move at the speed of light regardless of your motion prior to said event while everything else observing it sees it slower. Because the speed of light is constant and nothing can move faster than it. This raises another question. If this is so; your moving at the speed of light and you move just your hand, will time then slow down for the rest of your body as your hand is moving? I am very lost.