Interstellar Visitors, Just Passing Through: Fact, Fiction, and Arthur C. Clarke’s Rama Series

Probably the best known story of an interstellar visitor “just passing through” is Rendezvous with Rama (1973) by Arthur C. Clarke. The novel won a slew of awards, including both the Hugo and Nebula. Clarke’s tale starts with events much like this recent discovery: Our own Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) is designed to detect and track moving objects in space, and its primary mission is to find “Near Earth Objects” that might collide with our planet. In Clarke’s novel, there is a similar system called Spaceguard. The fictional near-future Earth government is a little more motivated to look for asteroids in the wake of a major disaster in 2077, when an asteroid struck Italy. Spaceguard first detects the object—later named “Rama” (after the Hindu god)—in 2131. (Interesting that both real and fictional objects are given names from non-Western cultures.) Rama, like ’Oumuamua, comes from interstellar space and will return there after passing through our solar system, and is thought at first to be an asteroid. However, images from an unmanned probe sent to Rama reveal that it is a perfect cylinder 34 miles long and 12 miles in diameter.

Only one ship in Earth’s space fleet is close enough to reach Rama before it leaves the solar system. That ship, the solar survey vessel Endeavor, is sent to intercept the alien craft. When they reach Rama the Endeavor scientists find their way inside through one of three airlocks grouped together. They discover the object has a hollow interior with a breathable atmosphere; the cylinder’s rotation also provides artificial gravity. They find “cities” full of “buildings” and machines but no sign of whoever built the object. When Rama starts preparing to accelerate out of the solar system, the scientists retreat back to the Endeavor with little understanding of the purpose or workings of the discoveries they’ve made. The ship and its builders remain enigmatic to the reader as well, and that persistent sense of wonder and mystery is one of the things that makes the book great, and still fairly effective after four-and-a-half decades.
One pattern that the scientists do observe is that structures in Rama usually came in groups of three—like the airlocks. The book ends with the line:
And on far-off Earth, Dr. Carlisle Perera had as yet told no one how he had wakened from a restless sleep with the message from his subconscious still echoing in his brain: The Ramans do everything in threes.

Certainly sci-fi is a genre known for doing things in three, though Clarke has said Rendezvous with Rama was intended as a standalone book, and denies the last line was intended as a hook for a sequel. And it was 16 years before the sequel, Rama II, finally appeared, and not one but two more books followed, The Garden of Rama and Rama Revealed. All three sequels are credited to Clarke and Gentry Lee, a writer and a chief engineer at the Jet Propulsion Laboratory. Reportedly, Lee did most of the writing, with Clarke supplying ideas. In Rama II a second cylindrical ship appears, 70 years after the first one. (Presumably a third will follow someday, but that’s not part of this story.) This time around, a handful humans wind up leaving the solar system on the craft. As a result, the three sequels tell us a great deal about the Ramans, and about galactic civilization in general. Whether finding out the truth behind the mysteries improves the first book or hurts it is left to readers to decide.
Unfortunately, there is no way we can get even an unmanned probe anywhere near ’Oumuamua, but its discovery is a nice reminder of the amazing scale of our universe. Scientists estimate there could be as many as 10,000 objects from interstellar space flying through our solar system inside the orbit of Neptune, with about three leaving and three more entering every day. Someday, presumably, humanity will have the opportunity to study one of those visitors. And it would be really exciting if one of them turns out to be an alien spacecraft.
Of course, it might also signal the end of human civilization. You never know about these things.
What’s your favorite story about a mysterious alien object?