According to the theory of relativity, as an object approaches the speed of light, time dilation occurs. Time dilation means that time appears to pass more slowly for the moving object relative to a stationary observer.
If you were to travel at the speed of light, time dilation would be extreme. From your perspective, time would effectively stand still. However, from the perspective of an observer on Earth, time would continue to pass at its normal rate.
To quantify the time dilation effect, let's consider a scenario where you travel away from Earth at the speed of light and then return. For the sake of simplicity, we'll ignore the fact that it is not currently possible for massive objects with mass to reach or exceed the speed of light.
If you were able to travel at the speed of light and then return to Earth, from your perspective, the journey would be instantaneous. However, from the perspective of observers on Earth, time would have passed normally. They would have experienced the duration of your journey, which would depend on the distance you traveled.
To calculate the time elapsed on Earth while you were gone, we would need to know the distance of your journey in Earth's frame of reference. However, please note that as an object with mass, it is not possible for you to travel at the speed of light, and the time dilation effects described here are purely hypothetical for the purpose of understanding the principles of relativity.