How could traveling the speed of light lead us to time travel?

gcolor7of12 asked:

In a question, someone answered that if we were able to travel the speed of light, then we could somehow achieve time travel. How would this happen?

Also, how could we make time travel possible? Is there some formula to it? I think time travel is a really awesome concept, and I want to learn more about it.

How long to travel to Mars from the point of view of those traveling?

T G asked:

I’ve heard that it will take roughly 9 months to travel to Mars. But, time travels faster when farther away from large gravitational fields. How long will it take from the point of view of an astronaut making the trip? What will be the maximum difference in the speed of time from an astronaut on the journey from the speed of time at mission control on earth?