For example, if I was on a rocket to mars and transmitting a video stream back to earth non-stop for the duration of the journey…
At the begining when I am leaving earth, the lag between me transmitting the video and earth recieving it would be basically nothing. But by the time I get to mars there is a delay of 3 minutes or whatever between send and recieve.
What happens to the video during the journey? Do some frames randomly drop? Does the video have to buffer constantly? Is there an incremental decrease in quality over time?
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>Is there an incremental decrease in quality over time?
That’s probably the closest of your descriptors to what actually happens.
Think of it in a relativistic sense. The rocket is transmitting constantly, so the data will be received constantly (ideally, ignoring the many other possible reasons why a signal might get lost).
But what will happen assuming that we’re talking about data being sent via radiowaves, is that the radiowaves will be [redshifted](https://en.wikipedia.org/wiki/Redshift) slightly due to the object’s motion. There’s also redshifting and blueshifting that happens up and down a gravity well; I don’t know which would be more dominant in this instance, but that’s how the distance would change the signal over time.
These redshifts are small. Very small.
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Now, if this were, like, a two-way video call, it wouldn’t *per se* be a matter of *buffering*, it’d be a matter where the *actual time delay* would just slowly get bigger and bigger, day by day as the rocket went on. As in, by the time the rocket gets to Mars, the things Earth observers would be seeing on their screens would *actually* be the events going on ~20 minutes ago (20 minutes is the average time delay between Earth and Mars). Any reactions they had, would be to events going on 20 minutes ago, and Earth’s reactions, from Mars’ perspective, would all be reactions to events that took place 40 minutes ago.
So let’s say that you and a person on Mars agreed to meet up at the same time. You’d both walk up to the screen at the same time, but neither of you would see the other’s faces, until 20 minutes, because the “feed” would be running 20 minutes behind realtime, and you wouldn’t have any way to speed it up because literally the data hasn’t gotten there yet. So after sitting there for 20 minutes, the two of you would see each other walk up, 20 minutes “late”… except that you both know that’s just how time works. And maybe you’d both say “Hi!”… but all you’d actually see of each other, would be the 20 minutes you just spent sitting there waiting for the other person to walk up. 20 *more* minutes would pass, and then, finally, 40 minutes later, you’d see each other’s responses.
At this amount of time delay, you just can’t realistically have a real-time in-person conversation. It’d be way more efficient to just send short video messages and communicate that way.
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