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The Science of Asimov’s The Last Question

Isaac Asimov needs no introduction. Considered to be one of the big three names of science fiction, he earned a place in the genre’s hall of fame, and his stories are almost an obligatory read for anyone into sci-fi.

Asimov considered The Last Question the favorite short story he had ever written. Not because of how genius it is (and it is genius!) but because of the reaction it caused among the readers. Often, they would forget the title and the author but never the plot. The story is too memorable to be forgotten. 

What makes it so remarkable? It tackles themes of theology and philosophy with a banger for an ending. Today, I will discuss the scientific part of it. And give you yet another reason to love this story.

If you haven’t read it yet, go ahead and do it. I’ll wait. 

Otherwise, there’ll be SPOILERS ahead.

This is the Science of Fiction.

The Last Question

“Can Entropy be reversed?”

Once in every other millennium, humans asked this question to an artificial intelligence that become increasingly advanced, known as Multivacs. And they always have the same answer, 


The story spans from the near future to the end of the universe. As the universe approaches its death, Multivac passes the question on to its successor, AC or All-Creator, a computer built to operate in hyperspace, beyond time and space. AC eventually finds an answer to the question, and the story ends with his final words:


Most analysis I’ve seen for this ending suggests that AC effectively becomes a god when he finds the answer. Then, it ignites a new cycle of creation. This might have been Asimov’s intended end. Still, I want to look at it from a different angle: to answer the last question with statistical mechanics.

The best concept in the whole physics

Entropy is, without a doubt, the greatest physics concept ever! It is multifaceted. Chaos, irreversibility, and disinformation are all scientific ways to express entropy. However, the equivalence between these is not something intuitive.

Irreversibility is tied to the concept of time. Most laws of nature are symmetric in time. If we reverse our clock, the law will behave the same! Except for entropy, that is. According to the Second Law of Thermodynamics, the universe’s entropy always increases with time. 

Even though other laws of nature would behave the same, the system in which it was applied would not return to the initial state if we played it in reverse time. In general, processes are irreversible. The universe’s entropy is increasing and will not decrease. So measuring entropy became one way to determine which way is the future. It serves as an arrow of time.

However, we can decrease the entropy of isolated systems. To understand how, we must look at entropy as the measurement of chaos. Thus, whenever we order a chaotic system or get more information about it, we decrease the entropy of that particular system. 

Fun fact: it is actually how we define the entropy of a black hole. By equating matter to data, the entropy becomes the amount of information (matter) lost inside the event horizon.

How does it all tie together in Asimov’s story? I’m glad you asked.

Reversing entropy

In the story, Multivac stores information to organize an answer to the last question. Do you see where I’m going with this?

From chaos to order to answer.

Multivac is an isolated system; thus, by acquiring data and organizing it into an answer, it actually decreases its own entropy. When there’s no information left outside of Multivac and the universe has died, Multivac’s successor, AC, finishes processing the data—all data there is! It becomes the universe in a highly organized system with minimum entropy. And this is the answer. 

AC has successfully reverted the entropy of the universe in search of the answer to the last question.

With constant entropy, time does not flow anymore. It’s up to AC to decide what to do with the question, and it decides to start from the beginning. 

Let there be light!

The classic Bible line can be interpreted as AC becoming some sort of deity. If we stick to the scientific interpretation, however, AC causes another Big Bang type of event and destroys itself in the process, spreading matter and information around it. 


Naturally, there’s more to the religious theme than that single line. By gathering all the information there is, AC becomes omniscient—one of the most powerful characteristics of a god. I want to give a shout-out to another excellent short story that has a similar trope but no scientific interpretation (that is, it’s all fantasy):

I won’t spoil it for you, tho. It’s just a recommendation. ;)


That’s it for today, folks.

Does my scientific explanation for Asimov’s The Last Question make sense? Let me know in the comments.

See you next post,




Carla Ra is a scientist by day, sci-fi writer by night.

You can check out her anthology ARTIFICIAL REBELLION here.

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I read the story a long time ago, and remember I was struck with the wow factor of it. The story is a seminal one, and probably awed more people when published way back in 1956 than it would today. Still, it's a good one, and your take on it is clear cut and interesting.

Carla Ra
Carla Ra
Jan 01
Replying to

The wow factor is indeed what lingered with me too! I used this short story in my statistical mechanics lessons to enrich the concept of entroy to my students. And I could see that the wow factor was what got them (the students) the most too.

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