First published in Science Fiction Quarterly (November 1956 issue), by Isaac Asimov. This story is the most well-known story by Dr Asimov, as well as one of his favourites. He reportedly was asked constantly about the name of the story, because people would remember the Wham Line, but forget the title.
The first time humanity asked Multivac the titular question was when two technicians, Alexander Adell and Bertram Lupov, were celebrating Multivac's solution for solar power on 21st May 2061 (the celebration has lasted for seven days). The energy that Multivac can generate from the Sun is orders of magnitude more than Earth can generate from coal and other non-renewable resources. Adell says they have enough energy to last forever. Lupov contradicts them, saying that it will only last for billions and billions of years but that entropy means we will run out of energy. So the two technicians challenge Multivac to learn whether entropy might be reversed. Multivac's answer is, "INSUFFICIENT DATA FOR MEANINGFUL ANSWER."
Far into the future, a family of pioneers, Jerrodd, Jerrodine, and Jerrodette I and II, have exited hyperspace near their new home; planet X - 23. A casual mention of entropy by Jerrodd has upset his daughters, so they ask Microvac if entropy can be reversed. Reassuring his daughters that Microvac has solved everything, he puts them to bed. Before disposing of the answer, Jerrodd reads the answer again, "INSUFFICIENT DATA FOR A MEANINGFUL ANSWER."
Even further into the future, two people, VJ-23X of Lameth and MQ-17J of Nicron, are preparing a report for the Galactic Council about humanity's rate of expansion in the galaxy. They realize that the rate of energy expenditure is even higher than the rate of human expansion. VJ-23X jokingly suggests that MQ-17J asks the Galactic AC if entropy can be reversed. It answers, "THERE IS INSUFFICIENT DATA FOR A MEANINGFUL ANSWER."
Jumping ahead again, we meet Zee Prime and Dee Sub Wun, who are essentially Energy Beings because their immortal bodies are left alone on planets while their minds are free to traverse the galaxies. In a fit of curiosity, they ask the Universal AC to show them the original galaxy from which humanity was born, then ask to see the original star. Of course, this is so many millions of years into the future, the sun is now a white dwarf, and Zee Prime becomes depressed, realizing that all the stars will burn out. So thy ask the Universal AC how they might reverse entropy, and it answers, "THERE IS AS YET INSUFFICIENT DATA FOR A MEANINGFUL ANSWER."
It is Just Before the End now, and Man is the only person left; a compilation of the minds of trillions upon trillions upon trillions of human beings. Man speaks to the Universal AC three times to request an answer on how entropy might be reversed. Each time, the answer remains the same; "THERE IS AS YET INSUFFICIENT DATA FOR A MEANINGFUL ANSWER."
After the End of the universe, all data has been collected. Space is gone, and Time has disappeared with it. Ten trillion years was not enough to determine an answer to the last question. But the data had not been comprehensively correlated, so the Cosmic AC spends a period of contemplation sorting through the data and seeing how it all fits together. Finally, an answer is determined, and the AC considers the formless void that once held a universe. To properly answer the question, it would become a Universe again, And AC said, "LET THERE BE LIGHT!" And there was light.
"The Last Question" has been adapted into several formats, such as audiobooks; Isaac Asimov Himself (1975, read by Isaac Asimov), The Last Question And Other Stories (1975, written by Isaac Asimov and read by Jim Gallant), Science Fiction Favorites (1975, read by Isaac Asimov), and The Drabblecast (episode #200, March 2011). It has been adapted into multiple planetarium shows, including one with Leonard Nimoy as the Narrator. It was adapted for Radio broadcast by BBC in 2008 and narrated by Henry Goodman. Finally, it was republished thirty times, and Dr Asimov would collect it in ten of his Anthologies; Nine Tomorrows (1959), Opus 100 (1969), The Best Of Isaac Asimov (1973), The Edge Of Tomorrow (1985), The Best Science Fiction Of Isaac Asimov (1986), Robot Dreams (1986), The Asimov Chronicles (1989), The Complete Stories, Volume 1 (1990), Foundations Friends: Stories in Honor of Isaac Asimov (1997), Its Been A Good Life (2002).
"The Last Question" contains examples of:
- 20 Minutes into the Future: The story opens in 2061 AD, over a hundred years into the future from when this was published, and still somewhat similar to modern day, while characters celebrate that all energy generation has been changed over to a version of solar power that is sufficient for all the world's needs. The next scene jump, however, places the setting many thousands of years in the future.
- Absent Aliens: Aliens are never seen, despite the story taking us all the way to the end of the universe. Humanity is allowed to freely colonize the entire universe with casual intergalactic travel.
- Absurdly Huge Population: Just before the end of the universe, it is populated by "a trillion, trillion, trillion" people, spread all over the universe.
- After the End: The last scene takes place after the heat death of the universe. Humanity is gone and only the Cosmic AC is left, existing only in hyperspace. The universe has deteriorated into a formless Chaos, a void of all things. Having finally solved the last question ever posed to it, the Cosmic AC says, "LET THERE BE LIGHT."
- Ascend to a Higher Plane of Existence: Ironically, it is the successor to Multivac, a computer the size of a small city, that first ascends, being built within hyperspace to become more efficient. Humans manage to ascend to Energy Beings, and then merge with the Universal AC to ascend again.
- Beeping Computers: (Subverted Trope) When Multivac is seen at the start of the story, it is softly clicking (and some lights were flashing) because it was sorting routine data. When Adell and Lupov asked it the titular question, "The slow flashing of lights ceased, the distant sounds of clicking relays ended." Later iterations of Multivac are so complex they don't make any noise except for speaking naturally with the human users.
- Benevolent A.I.: Multivac is so human-focused and helpful that even after it guides humanity and its descendants all the way until the end of the universe, there was one question it never answered. The Last Question is if it is possible to reverse the effects of entropy. In order to fully answer that, the computer becomes God and recreates the universe so that there is a humanity that it can give the answer to.
- Blatant Lies: Jerrodd lies to his children, telling them that the Microvac running their spaceship has already figured out how to prevent the stars of the universe from dying due to entropy. Telling them the truth would have upset them further, and he's trying to get them to bed.
- Caused the Big Bang: The titular question refers to humans trying to figure out how to reverse entropy, the heat-death of the universe. By the end of the story, the massive human-designed computer Multivac has figured out an answer, but the universe has already died. So it recites from Book of Genesis, "LET THERE BE LIGHT!", implying the creation of a new universe.
- Casual Interstellar Travel: The second scene involves FTL through hyperspace, an invention by the Planetary AC computers which allow humans to colonize new worlds. This, along with immortality, begins to cause new issues as the population of the galaxy is increasing rapidly. The fourth scene has Energy Beings of mankind which can traverse intergalactic distances with only the effort of their minds.
- Deity of Human Origin: (Played With) Humanity builds a supercomputer of unparalleled processing power and keeps upgrading it over millions of years, asking the eponymous question ("How can the net amount of entropy of the universe be massively decreased?", that is, violate basic laws of physics and enter god territory) from time to time. The answer is always "INSUFFICIENT DATA FOR MEANINGFUL ANSWER." This remains the answer even as the computer grows exponentially more powerful as the story progresses through the gradual heat death of the universe, and even when the Universe is completely dead and the computer was the only thing left in existence (its hardware had transcended matter and energy and been hidden in hyperspace long before that point), it still doesn't know the answer. But the computer keeps working on it until it does find the answer, so the story ends with "And [the computer] said, "LET THERE BE LIGHT!" And there was light-"
- The Determinator: Towards the end of the story Cosmic AC admits to man that it has been working on the last question continually for the hundred billion years since it was first asked, and it will continue to do so until it has an answer.
- Deus Est Machina: Quintessentially, the Cosmic AC, to the point where, after all the stars have gone out and the universe has died of entropy, it recreates the universe with the line, "LET THERE BE LIGHT!"
- Driving Question: A succession of people attempt to get Multivac to answer this question, "Can entropy be reversed?" As it turns out, yes it can.
- Expositron 9000: Humans build increasingly advanced computers and, every so often, ask them whether the heat death of the universe can be reversed. The computers always say something similar to "INSUFFICIENT DATA FOR MEANINGFUL ANSWER." It's only after the universe has ended, when the only thing left existing is the single cosmic-scale computer with its circuitry in hyperspace, that the question is finally answered.
- Family Theme Naming: Jerrodd, Jerrodine, and Jerrodette I and II are a father, mother, and two daughters whose names all begin with Jerrod.
- Fantastic Naming Convention: The changes in names are used to help illustrate the different periods of growth the universe goes through:
- First, Alexander Adell and Bertram Lupov are normal enough names, indicating events are 20 Minutes into the Future.
- Next, Jerrodd, Jerrodine, and Jerrodette I and II, a presumably average family, indicate that things are still somewhat recognizable, but also begins incorporating You Are Number 6 for the futuristic elements.
- Next, VJ-23X of Lameth and MQ-17J of Nicron appear in the next segment, showing a trend towards names becoming designations rather than words.
- Next, Zee Prime and Dee Sub Wun, whose names sound like Z' and D1.
- Last, Man; because all humans are one human, each ageless body ascended to live as Energy Beings that have merged into one person.
- The Future: Aside from the first scene, which is set roughly a hundred years into the future, human society is supposed to seem less and less recognizable as the generations of Multivac are replaced. First there's family-owned spaceships with voice-controlled systems incorporating an artificial general intelligence that includes an internet fifty generations in the making, Casual Interstellar Travel, and Fantastic Naming Convention. Later scenes become more and more fantastic.
- Godhood Seeker: The Cosmic AC, a Master Computer for the universe, has figured out how to become God and does exactly that.
- Just Before the End: The second to last scene takes place just before the heat death of the universe. In each scene, a human (or a descendant thereof) asks Multivac (or a descendant thereof), "How can entropy be reversed?". The last scene is After the End, and that's when the last question is finally answered; "LET THERE BE LIGHT!" And there was light.
- Master Computer: Each version of Multivac seen in this story is larger and larger (except for the very second one we see, the Microvac, due to miniaturization). The first one starts out measured in miles. The successive versions end up existing only in hyperspace because otherwise it would be so large that the speed of light would slow down its processing.
- Merger of Souls: Just before the end of the universe, the essential souls of mankind had already merged together to a single consciousness, but on-screen we see each of the remaining humans merge with humanity's hypercomputer, the Cosmic AC.
- Natural End of Time: Multivac is often asked if entropy can be reversed, forestalling the end of the universe. Despite turning into a Galactic AC, existing entirely in hyperspace, it fails to prevent the universe from dying. But it does figure out a solution, and is able to create a new one to replace it.
- Not Quite Forever: The whole plot of Isaac Asimov's The Last Question starts with this trope:Adell: All the energy we could ever use, forever and forever and forever.
Lupov: Not forever.
Adell: Oh, hell, just about forever. Till the sun runs down, Bert.
Lupov: That's not forever.
Adell: All right, then. Billions and billions of years. Twenty billion, maybe. Are you satisfied?
Lupov: Twenty billion years isn't forever.
- Really 700 Years Old: Both VJ-23X and MQ-17J seem to be in their early twenties, but VJ-23X is two hundred twenty-three years old and MQ-17J is just under two centuries old.
- Shout-Out: The final lines of the story are drawn from the first chapter in the Book of Genesis; "LET THERE BE LIGHT."
- Small Universe After All: At some point in the distant future depicted by this story, mankind will develop intergalactic travel to the point where characters can casually communicate and move to different galaxies (so casually, that each one is simply "the galaxy").
- Solar CPR: This story follows the potential future of humankind, showing different eras where characters realize that the stars will run out, and they ask their ever-more-powerful general-purpose AIs how to restore the energy of the stars. Or, put another way, "How can the net amount of entropy of the universe be massively decreased?" It takes longer than the lifetime of the universe that is, long after the stars have gone out to come up with an answer.
- The Stars Are Going Out: Characters, concerned that stars will inevitably die, ask ever more-powerful computers how to restore the energy of the stars and reverse entropy. It takes longer than the lifetime of the universe that is, long after the stars have gone out to come up with an answer. Yes, it can. The story ends with the now bodiless and omniscient computer proclaiming, "LET THERE BE LIGHT."
- Standard Sci-Fi History: The story starts with Earth celebrating the total conversion to solar power (a method devised by Multivac which is far more efficient than current solar cell technology). The next scene has jumped to interstellar exploration with the Jerrod family moving to X - 23. Next comes a pair of character writing a report for the Galactic Council on the projected rate of expansion within The Milky Way Galaxy. This council never really seems to fall apart, merely dissolve into uselessness as mankind acts more like Energy Beings. By the time the universe is ending, there are over a trillion, multiplied by a trillion, multiplied by a trillion people in it. Aliens are never seen and this story goes much further along the path of history than comparable stories.
- Time Abyss: The AC has the memories of the first Multivac on Earth. The story ends some unspecified (but extremely long) time after the heat death of the universe.
- You Are Number 6: Each scene makes use of a different Fantastic Naming Convention. The second scenes have Jerrodettes I and II, the third introduces VJ-23X of Lameth and MQ-17J of Nicron, and the fourth has Zee Prime and Dee Sub Wun, whose names sound like Z' and D1. The names become gradually more inhuman to represent that the descendants of humanity will seem more and more inhuman the further they are displaced in time from us.
- Wham Line: The story features a series of ever-more-powerful computers, who are each asked the question, "How can the net amount of entropy of the universe be massively decreased?", in the context of averting the heat death of the universe. The answer always comes back "INSUFFICIENT DATA FOR MEANINGFUL ANSWER.", until the final iteration of the computer, a hyperspace-based computer called the "Cosmic AC" who has survived the heat death of the universe. It concludes that it must demonstrate the reversal of entropy in order to properly answer mankind's question and says, "LET THERE BE LIGHT!"