My first Hugo nominated story was focused on light sails. (Pun halfway intended.)
And now, a quarter of a century later, genuine science has supplied a smaller scale, protagonist free, and far more believable scenario than the grand, world-shaking events that I dreamed up.
If I was setting the odds, I'd give Oumuamua a one-in-five chance of being artificial. But that number, clinical as it pretends to be, has been twisted by my own biases towards alien contact, as well as a fondness for one-in-five guesses. (A 20 percent chance? Well, you're not predicting that it can actually come true. And if it doesn't happen, nobody should chide you for being wrong either.)
But imagine that Oumuamua is alien.
A 60 meter light sail, disk shaped and tumbling, and ancient, and dead.
Its very presence is amazing. That's because we shouldn't be able to see it. Because space is huge. Hollywood and most everyone else envisions space as being a big, big ocean. That's why space battles in movies look like ships at sea, with fighters thrown in for speed. But the reality is that every distance is enormous, and light is stubbornly slow. Make estimates about life in the cosmos and the rise of alien intelligence, and you don't expect to look at the sky and see this kind of object so quickly. But that's what happened. A new telescope opened its eye and almost immediately spotted an object of these dimensions -- a question mark that passed within 15 million miles of the earth, that approached the sun closer than Mercury does. That implies that if we keep watching, bringing newer telescopes into play, we will soon be seeing a host of objects like Oumuamua.
So is that what will happen?
Ten years from now, will we have named dozens or hundreds of oddities, each of which is silently passing inside the orbit of Neptune?
That sort of alien detritus implies that many ancient objects will have hit the earth, and I would think that even at these fantastic velocities, there would be physical remnants of odd materials, high-technology fossils waiting in ocean sediments and in the limestone blocks inside your garden wall.
And of course if that's proven true, then the next great question is:
Where did all of these aliens go?
The central question for humanity. Now, and always.