Interstellar Communication Failures - The Pioneer Plaques.
Imagine if you were a humanoid species which was part of a collective, living somewhere in the galaxy close to our solar system. Your race, as an intelligent body, stands along the time-line of our early space age, somewhere through to this current day.
On a routine space mission, you encountered on radar a foreign object traveling through your area. Your space mission is successful in retrieval of this dormant object. You return it to home base. When your scientists examine it, they find this image:
If I was one of those scientists, maybe I think this way:
The first thing I notice are the 'people.' Then, I see the thing behind them. Then, I see the diagram below of what might be a solar system. Then, I notice the line where the thing behind them is moving. I see the thing behind them looks just like what was just picked up . . . and then, I start wondering whether they created a giant version of the thing behind them, and then I wonder if that thing's coming for me. Maybe they also have huge 'people' with it, too. I mean, they're huge. Look at them! Their genitals are probably around the size of moons or planets.
What is that thing to the left, where it's got a bunch of lines from an origin? Hey, maybe they shot a bunch of these gigantic things into space.
Maybe that thing in the upper left is their eyes.
They're watching us, man! And, they're going to send a bunch of gigantic things with big people to smash us!
Although the message was designed to encode the most information possible in minimal space, rather than to be easily readable, almost none of the human scientists that were shown the message were able to decode all of it.