I’m writing a philosophy paper and need a little help with some maths on Time.

To use the example within the documentary “The Illusion of Time” (Example Link:

https://www.youtube.com/watch?v=YRwZ55zjzxc - Example illustrated From: 24:15min – 26:50min in the vid). The presenter explains how if we are standing at Point “A” (lets say us on earth), and an Alien is standing at Point “B” 10 billion light years away from us, that if the alien gets on a bike and starts riding away or towards us at a speed then the Aliens perception of “NOW” time would change possibly as drastic as being 200 years in the future or past, depending on the direction the Alien was to ride.

My question is, while I’m sure there isn’t a simple equation… is there possibly a simple equation that can help explain this effect?

Possibly an equation that shows, if the distance between point A and point B is “X” distance, and the Alien at point B moves directly further away (being a positive speed), or closer towards (being a negative speed), over a total distance of “Y” then when the Alien stops moving how much would it’s “now” time have change (in terms of seconds) compared to the person who stayed still at Point A.

I'm no physicist but I'd really like to find a simple way of explaining this phenomenon and showing it's working through numbers to use within my paper about Time and our perceptions of it.

If anyone out there can help that would be amazing!!!!

Many thanks,

- Anthony