It’s 5,000 light years away, but they are somehow able to communicate to us that “we see you and we’re on our way to say hi. See you in 50,000 years or so!” How do we react? Does that incentivize us to behave differently to preserve our species so that we are around when they come? Or does it divide us and lead to an early(ier) demise? Or does it not change us at all?
In a couple of generations it will be reinterpreted ten times over, then finally dismissed as a hoax.
So, ten times longer from now than our entire civilization has existed?
You might as well ask early Bronze Age hunter-gatherers what they plan to do about global warming.
If we won’t do that for ourselves, why would we do that for some beings we don’t even know?
OTOH, knowing that there’s life out there might incentivize us to invest more in space exploration.
That’s a tomorrow problem.
Well, It’s like doing the vacuuming because a visitor is coming over isn’t it? I don’t mind coexisting with a lot of dust and cobwebs, but I’ll get rid of it for guests, except really close friends who I know don’t care.
It’d be really embarrassing if an advanced civilisation came round and we’d wiped ourselves out by our inability to keep the planet nice.
Is that all the message says? I feel like that would be first very exciting, but quickly also disappointing. Also if they’re 5000 light years away, how did they see us?
Assuming we believe it’s genuine, a message that something will happen so far in the future will not change anything. I don’t think we’d see any major change or planning if the timescale was as short as 500 years.
Well, they’d likely see primitive humans, but could deduce that we’d have evolved well enough to detect their signals by now? I was trying to come up with a scenario that could actually happen based on the galaxy as we know it, and assumed speed limitations of ships flying through space. Perhaps an advanced civilization could be closer and we can shorten my assumptions.
Modern civilization is incapable of planning for anything 50 years from now.
Maybe the message was sent to another species. They might be disappointed and pissed off that all the Wooly Mammoths were killed of by us.
More like the next quarterly report. 
Or in some cases, two weeks.
I was supposed to go to the hospital for an operation last week. I got all prepared and ready and then the surgery got postponed. Now I feel like a chump.
So what happens if we wait 50,000 years and they send a message like “Sorry, the cat has the flu; see you in another rotation of the galaxy”?
Perhaps this civilization simply makes a habit of broadcasting their travel plans all the time… or their expansion plans, telling any and all civilizations who receive it “hey, have some infrastructure prepared for us by the time we arrive, maybe we’ll just trade for what we need rather than having to conquer and uplift you.”
Everyone who ever had a notion to believe in wacky conspiracy theories would now feel vindicated.
Or will believe this is just another government plot where the message is fake, but is intended to provide justification to do [whatever] evil to the People.
Recall the many people who said COVID was a hoax to make everyone wear masks. Exactly how everyone wearing masks advanced some evil government goal was a question they could never really answer. But they were sure that’s what was going on.
If people can dismiss a real pandemic with lots of dead people as a fake, how much easier to dismiss a message that some agency supposedly received from some aliens?
Make up the guest bedroom, put out fresh towels, and make sure the bar is well stocked.
Perhaps they send reminders every 100 years or so. Like a countdown for us.
Many people suspect that life must exist elsewhere, but we’ve never found any, not even simple forms of it, but to know for certain that there is another intelligent species? That’s gotta have some impact. Some people will turn to religion, while others might turn from it. Some will want to kick start space exploration, while others may want to hunker down and protect our homeworld against any perceived threat.
Sure. It would affect how we think and do so much, just as nuclear weapons affects everything to do with war, and birth control affects everything to do with men and women.
But it wouldn’t be so clear what the effects were. Would religion have been stronger or weaker without the messages from distant civilization(s)? It would be impossible to say, other than that it would have been different.
As for the period of 50,000 years, this is enormous in terms of cultural and historical change on earth (and likely in the distant advanced civilization as well). Even 100 years will see enormous cultural and historical change. There probably will be, from the way I would judge it, recurrent dark ages and times of progress. The signals from both sides will radically change over time, and thus the cultural impacts.
In another 200 million years? I, for one, never plan that far ahead.