According to our current understanding of physics, it is not possible for an object with mass to travel at the speed of light. As an object with mass approaches the speed of light, its relativistic mass increases, requiring an infinite amount of energy to reach or exceed the speed of light. This is known as the mass-energy equivalence principle, represented by the equation E = mc², where E is energy, m is mass, and c is the speed of light.
However, let's consider a hypothetical scenario where you could travel at the speed of light. In this case, according to the principles of special relativity, time dilation would come into play. Time dilation states that as an object approaches the speed of light, time appears to slow down for that object from the perspective of an observer at rest.
If you were somehow able to travel at the speed of light, time dilation would cause time to stand still for you. From your perspective, the journey would be instantaneous. However, from the perspective of an outside observer, time would continue to pass at its normal rate. Therefore, the outside observer would not perceive you as having returned before you left.
It's important to note that the concept of traveling at the speed of light with mass is currently beyond our technological capabilities and is prohibited by the known laws of physics. The discussion of what would happen under such conditions involves hypothetical scenarios and the theoretical predictions of special relativity.