I’m a writer. I'm working on a story. It’s sold actually, but they want some changes and I’m trying to figure out the science..
IDEA:
A distant planet picks up broadcasts from Earth, so the inhabitants have some knowledge of us, and know that life is out there. A "man" on the alien planet gets part of his consciousness encoded into a light beam that is sent out into space.
When it hits earth -It is able to project itself and appear to be human. When the light fades the man vanishes, leaving a message that he is long dead. (It's a love story.) But the question is what broadcasts would he have received time wise. His knowledge of earth would be limited, ending at a certain time...


This is the end/explanation.
Thank you in advance for your help!
“ My people developed a holographic beam so powerful it could be projected through space. Through light-years. It is more advanced than anything on Earth, so advanced that some actual particles of my being were intertwined with the particles of light being projected. So it was like
I was actually here, next to you, talking to you,
Laughing with you. But I was not. I am not.
“When we sent the beam of light traveling into
Space my particles were woven into it, not all of them, of course. But enough particles of my consciousness were intertwined with the particles of light so that I could interact with anyone I discovered.. . So that I could learn more about the world we’d previously only
Known through television broadcasts.. .
“I traveled in a spaceship made of light. Now that
The light has died so have the particles of my
Consciousness that were interwoven with the beam... The real 'me, ' the corporeal 'me,' died --- HOW MANY? Light years ago."


Long ago, men went to sea. And women waited for them, peering out into black waters, searching for a tiny speck of light on the horizon. Now I too wait, looking out into the vast blackness of space, searching for my love, my heart, HOW MANY? Light-years dead.


Thanks for any help with this. Elizabeth.

You should try to use an X factor of 2. If the planet is 35 light years from earth then it would be a 70 year round trip. So a signal that we would recieve today would have come to them from 1945 earth. You might want to watch the Jodie Foster movie Contact to get an idea of how it works for film.

I note that you are misusing the term "light year" - it is a measure of distance, not time. For example in the phrase: "The real 'me, ' the corporeal 'me,' died --- HOW MANY? Light years ago" you should just say "years ago," not "light years ago." Same with the last phrased: "light years dead" makes no sense.

Picking up on what Cdad said - if the planet the alien lives on is 100 light years from earth, it would take 100 years for the signal to go from his planet to ours. Thus at most he died 100 yeas ago. Depending on the expected life span of this race of beings he could reasonably predict about how long he would be dead by the time his transmission reached Earth. For example if you are 60 years old when you send a broadcast to a planet that is 100 LY away, you can reasonably guess that you may live perhaps another 40 years (to make it to age 100), which means you will have been dead for 60 years by the time the transmission reaches that other planet.