ZThemes
i'm just another human being among approximately 7 billions of other humans, lost somewhere in the infinity of the cosmos.. don't forget : Imagination is everything. It is the preview of life's coming attractions. - Albert Einstein

As you can see in diagram 1, within your reference frame, the light only has to travel up and down. But in diagram 2, from Einstein’s perspective, the light has to travel not only up and down but horizontally as well. Since the light has a longer distance to travel, more time is taken (remember that the speed of light is always constant!). Hence, the dilation of time.

As you can see in diagram 1, within your reference frame, the light only has to travel up and down. But in diagram 2, from Einstein’s perspective, the light has to travel not only up and down but horizontally as well. Since the light has a longer distance to travel, more time is taken (remember that the speed of light is always constant!). Hence, the dilation of time.