Suppose there's some sort of space exploration mission underway, consisting of launching some sort of large-ish unmanned thing towards say Jupiter or whatever.
Suppose that the mission fails, unexpectedly, and suddenly. Everything seems to be in order, the launch is successful, the instrument exits Earth orbit as planned, goes for a while, and then suddenly... there's an explosion.
But not any sort of explosion, mind you. A humongous explosion. The light of it is actually seen on Earth during the day, it blots out the Sun. Early estimates put the total energy released somewhere in the range of... one ZettaJoule. Yeah, that's right, 1021 Joules. One and 21 zeros. 1`000`000`000`000`000`000`000`000`000`000`000`000`000`000`000`000`000`000`000
Minutes thereafter, further explosions are seen, mostly on Jupiter, some on Saturn. Fortunately, the largest one, a few hundred times larger than the original, happens on the dark side of that planet, but the glare cuts a visible outline of Jupiter in the daylight sky. The electromagnetic storm ensuing ionizes the troposphere to the degree aurorae are a feature for months, all the way to the Equator.
Everybody promptly forgets about the lowly space mission, while for months the brightest minds on planet Earth scramble to figure out what to do while the brightleast minds on planet Earth scramble to "come up with policies", recognize each other for counts of minutes and thank each other for their leadership. Then one day, a chap nobody thought was particularly bright manages to add two and two together, and has an excellent story to tell the world :
On one hand, the suddenly missing craft weighed in at about eleven thousand tons. That, if one bothers to apply mass to energy conversioni would yield just about... one zettajoule. And should the craft in question have ran into a solid antimatter object, the resulting explosion could have conceivably fragmented it, and thrown it off its calculated course, enough so that the bits fell onto the nearby gas giant, causing all the other explosions. And it turns out that if you do a little geometric and gravitational modeling, it's quite plausible that in fact the object in question was just about a million tons give or take, and it was probably made of either anti-iron or anti-nickel. Or perhaps an alloy of the two. An anti-alloy.
And this anti-alloy chunk was coming straight for Earth, as it turns out, and it was painted black (except you know, with anti-paint, which isn't anti-black ie white, it's just anti-matter, but otherwise exactly paint) which is why nobody saw it. So conceivably, it was sent by a civilisation somewhere that has the technology to send large chunks of matter across space with the accuracy to make them home right on Earth, and is probablyii composed out of individuals more or less physically similar to humans.
So now the debate rages : what to do ? Was it intentional ? Should they be "punished" ? How would you know, and moreover, how does the deer punish the hunter, when but for the bullet holes it wouldn't even know there's a hunter there, and still can't make him out ?
But perhaps it was unintentional, and so the behaviour should be excused. Especially seeing how there's exactly jack shit one could do anyway. What's easier than ignoring large, flashing signs of danger ? And what's more specific, more aptly proper and characteristic of an extinct species ?
Obviously antimatter porn suddenly starts trending on derpix or whatever it's called, while the lowly probe that turned out to have serendipitously saved planet Earth from its programmed obliteration is retroactively rechristened as god, jesus and ghandi, and has a bunch of various sects "following it" and "interpreting" "its message" to mankind.
And so there you have it, a whole universe, but what's really valuable : a whole alt-universe built on a sustainable premise. It's reasonable, it makes sense, it's interesting, you can live a lifetime out of exploring the implications and intricacies attendant.
And... who knows, maybe you'd be doing future generations a favour.———