According to the theory of relativity, as an object approaches the speed of light, time dilation occurs. Time dilation means that time passes more slowly for the object moving at high speed relative to a stationary observer.
If you were able to travel at the speed of light for 5 seconds from the perspective of an observer at rest, from your own reference frame, time would appear to pass normally. However, from the perspective of the stationary observer, time would have passed differently due to time dilation.
The equation for time dilation is given by:
t' = t / √(1 - v^2/c^2)
Where: t' is the time experienced by the moving object (you, in this case) t is the time experienced by the stationary observer (the 5 seconds you mentioned) v is the velocity of the moving object (the speed of light, which is approximately 299,792,458 meters per second) c is the speed of light in a vacuum (299,792,458 meters per second)
Plugging in the values, we get:
t' = 5 / √(1 - (299,792,458^2 / 299,792,458^2))
Simplifying the equation:
t' = 5 / √(1 - 1)
t' = 5 / √0
Since the denominator is zero, the equation becomes undefined. This means that it is not physically possible for an object with mass, such as a human body, to reach the speed of light. The closer you get to the speed of light, the more energy would be required to accelerate you further, eventually becoming infinite.
Therefore, it is not possible to determine how much time would have passed from the perspective of an observer at rest if you were able to move at the speed of light for any amount of time.