If the journey is from here to Alpha Centauri, the time elapsed on their journey is 4.3 years
What is a light-year?
We define a light-year as the distance that the light moves in one year of time.
So, if someplace is at X light-years from here, it means that, at the speed of light, you would need to travel for X years to reach there.
From that, we can conclude that to reach Alpha Centaury traveling at the speed of light you need to travel for 4.3 years. So the time elapsed on the journey is 4.3 years.
If you want to learn more about distances, you can read:
https://brainly.com/question/803764
