Imagine being given the task of explaining the origins of an object to an unknown recipient. A recipient that doesn't understand your language, has no knowledge of your alphabet and not even a basic understanding of the symbols we all consider universal.
This might sound absurd but it was exactly the assignment Dr. Carl Sagan and Dr. Frank Drake set off to accomplish when starting design on what was to be known as the Pioneer Plaque.
To infinity and beyond
NASA's Pioneer program consisted of space probes being sent out to investigate celestial bodies. The Pioneer 10 and 11 would actually travel to the end of our solar-system and continue into deep space. Journalist Eric Burgess was the first to present the idea that the satellites should contain some information about their origin in case of alien interception.
What a design challenge! How on earth (pun intended) can you possibly imagine what it would be like for an alien to witness imagery from a totally unfamiliar world? Will they even have the ability to understand artistic renditions? It might seem obvious to us but the majority of beings on our own planet cannot. They did make a few assumptions that limited the challenge slightly. As the chance of the satellite ever coming in contact with an alien civilization was slim at best, they figured that the best chance would be for it to be picked up by an alien space-craft. This would mean the collectors weren't exactly cave-men.
And when watching the imagery it certainly seems decodable. While I don't instinctively catch the deeper scientific bits. I recognize the planets and the two human figures. So credit to Drs. Sagan and Drake and to Sagan's wife at the time - Linda Salzman Sagan who actually prepared the finished artwork.
The curse of knowledge
However: It is hard for us, as it was for the plaque's creators, to escape the curse of knowledge. We all know about the stuff the pictures are describing. The human figures are nearly instinctively obvious to us as we're trained to recognize other humans from the moment we open our eyes the first time. For otherworldly beings however all this could be potentially confusing. Just think back through our own history when [legend has it] that the Aztecs mistook the Spanish conquestador Cortes for a good when he unmounted his horse. We all view our world based on knowledge, culture, religion and other filters society have bestowed upon us. The earth used to be flat remember?
So to try to round this up the plaque-creators had a seemingly impossible task and they probably knew it. They gave it their best shot however and whether they succeeded or not we'll probably never know.
The point you should keep in mind is this: Your audience, whether you're making a speech, lecture or film, might be Alien Aztecs. They might be completely oblivious to what you trying to convey. Therefore you must try to put yourself in your audience's shoes. Otherwise you just might end up as an Aztec deity on The Forbidden Planet...