When we think of extraterrestrial intelligence, we tend to think of two main possibilities. The first is the possibility of mobile, fleshy, protoplasmic aliens not radically different from us (except that their arrangement of flesh would probably be very different). The second possibility is machine intelligence, would might be something like extremely intelligent robots. But there are other exotic possibilities which should also be considered.
One very strange possibility is that of a very massive and immobile extraterrestrial intelligence. Such an organism might have a sprawling body that stretches on for many hundreds or thousands of miles, either on the land of a planet or the bottom of one of the planet's oceans. Instead of having just one brain, the organism might have many different brains, each connected to the massive body. Viewed from above, the organism might look a group of human neurons, except that each node in the network structure might be an individual brain rather than just a nerve cell of a brain.
We can imagine something like the image below, with each white clump being an individual brain, and the networked structure stretching on for many miles. Such an organism might be far more intelligent than a human, and might last for thousands of years. If one of the brains was eaten by a predator, it would be no worse than a human losing a single brain cell.
Another exotic possibility is that of a a gaseous extraterrestrial intelligence. The possibility of a gaseous extraterrestrial intelligence was raised by astronomer Fred Hoyle in 1957, who wrote a science fiction novel called The Black Cloud, about a giant cloud of particles that invaded Earth. In Hoyle's novel, the swarm was a superorganism far more intelligent than a human.
The Orion Nebula (Credit: NASA)
A second possibility is that a gaseous intelligence might arise in some special atmosphere of an alien planet. We can imagine some strange alien planet with super-thick, long-lasting clouds, clouds that were rich with organic molecules. Such clouds might provide a stable environment for the evolution of a gaseous intelligence. But since such an intelligence would presumably not have any technology, we would never learn of its existence unless we traveled to the planet.
A third possibility is that some ground-dwelling extraterrestrial intelligence might deliberately convert itself into a gaseous intelligence for the sake of achieving immortality. This would be similar to what was imagined by Arthur C. Clarke in his novel 2001: A Space Odyssey. Clarke imagined super-advanced aliens who first evolved from protoplasmic bodies to robotic bodies, and then eventually evolved from robotic bodies to an immortal pure energy existence. The same goal might be achieved if an extraterrestrial intelligence were to deliberately evolve into a gaseous state.
Some would argue that a gaseous intelligent being is impossible, because particles have to be directly connected, like the neurons of a brain are connected. But physicists know of a strange thing called quantum entanglement, which allows for particles that are not physically connected with each other to be co-related just as if they were physically connected. Quantum entanglement might make possible intelligent gaseous beings.
If you were an extraterrestrial intelligence existing in a gaseous state, you wouldn't have to worry about various types of accidents killing you. In addition, you might be able to convert yourself back and forth from a gaseous state to a solid state. We can imagine gaseous extraterrestrials with the power to convert themselves into any type of animal known on their planet, or any gender, or a body just like that of any person who had lived on their planet.
If this possibility is real, then one day if extraterrestrials arrive on our planet, it might be nothing like the conventional notion of big-headed creatures landing on the White House lawn. Instead, the alien visitors might make their appearance on our planet as gaseous blobs in the sky. In such a case, the weather forecast might be: cloudy, with a chance of alien conquest.