Subjective time

Age is not a number

The Bible says:

The days of our years are threescore years and ten; and if by reason of strength they be fourscore years, yet is their strength labour and sorrow; for it is soon cut off, and we fly away.

I recently reached age 70, which has gotten me thinking about time. Have you ever thought about the phrase “time flies when you’re having fun”? Why is that? And why did time move so slowly at age 10 when I had all my cavities filled (by a sadistic dentist) without any painkillers? Perhaps we suffer because God doesn’t want us to be happy, he wants us to be good. Or perhaps evolution doesn’t want us to be happy, it wants us to avoid dangers and successfully reproduce.

Like most people, I’ve noticed that time seems to speed up as one gets older. I moved to California in 2017, and the past 8 years seemed to pass by very quickly. I feel like time is moving twice as fast as when I was 35. Even as a 16-year old high school student I had already noticed that those “long summer vacations” seemed to pass by at twice the speed as when I was only 8 years old.

In mathematical terms, subjective time seems roughly proportional to the inverse of one’s age. (At least since age 3 or 4, before that I recall nothing.) At age N, each lived year represents 1/nth of our life. If this is true, then this has some fairly startling implications.

I’ve noticed that some rationalists have a strong preference for life extension. They are depressed by the thought that their lives may soon end, and a few may even adopt strategies such as cryonics. Personally, I don’t feel that way, but I am not going to argue that they are wrong. Most people say they enjoy life, so why shouldn’t they wish to live much longer? A cultural conservative that scolds these rationalists for their “weird” preferences is often the same person that opposes helping a sick person die at 80 and believes that we should use modern medicine to create what the Bible suggests is an unnatural and painful extreme old age. Life extension technology is good, or it isn’t. You can’t have it both ways.

The good news is that our lives are not as short as they appear. My gut instinct is that my life has flown by rather fast, but this is a cognitive illusion. Our lives are far too vast for us to recall more than a tiny fragment at any given time. Indeed, even if we lived another 1000 years, it would make surprisingly little difference. Consider the formula:

Subjective time = 1/age

This means that a decade at age 100 feels more like a year at age 10. Part of that is because we slow down with age—less gets done in a given day. But I don’t believe that’s the main problem. Instead, experiences become somewhat repetitive as we get older. The first time I went to Italy, it was a mind-boggling experience, a whole new world opened up. The second time, things were much more familiar. And that’s true even if one visits a different part of Italy.

The first time you see a torrential rainstorm it creates a vivid impression. The same is true the first time you see a moon enshrouded in fog, or dust particles floating in a sunbeam, or the first time you walk on top of snow encrusted with ice without breaking through, or a thousand other observations about the world around you. As you get older, you barely pay attention to things that you would have been entranced by when young.

In A New Refutation of Time, Borges went even further:

I write it now as follows: The pure representation of homogeneous objects—the night in serenity, a limpid little wall, the provincial scent of the honeysuckle, the elemental earth—is not merely identical to the present on that corner so many years ago; it is, without resemblances or repetitions, the very same. Time, if we can intuitively grasp such an identity, is a delusion: the difference and inseparability of one moment belonging to its apparent past from another belonging to its apparent present is sufficient to disintegrate it.

It is evident that the number of such human moments is not infinite. The elemental ones—those of physical suffering and physical pleasure, those of the coming of sleep, those of the hearing of a piece of music, those of great intensity or great lassitude—are even more impersonal.

Even if one rejects the extreme claim that these repeated events are “the same” and that time does not exist, they are surely similar enough to greatly compress subjective time.

Imagine that you were born 10,000 years ago in one of the very first towns in the Eastern Mediterranean, say in Turkey or Syria, and were still alive today. At first glance, it seems like you would have been living for 100 times longer than almost any modern human. In fact, according to my subjective time formula, you would have lived barely twice as long as my 99-year old mother. As you got older, the years would have seemed to fly by more and more rapidly, like the fluttering pages of a calendar from one of those old Hollywood films. (My mom is 100 as Asians count their age.)

And why stop there? If we square 10,000 years, we get 100,000,000 years. In subjective terms, a person 100 years old has lived 25% of the life of a hypothetical human being born in the age of dinosaurs. Indeed, you’ve subjectively experienced almost 1/6th of the entire history of the universe!

There’s a theory that universes are continually being created by the process of natural selection. Those that “reproduce” (i.e., produce new universes out of black holes) are favored over those that do not. From a certain vantage point, the age of each universe seems to pass by in the blink of an eye. Like the Aleph, in Borges’s famous story.

This universe may continue for trillions or quadrillions more years, but (unless I’m mistaken) the anthropic principle suggests that it’s very unlikely we’d have been living this early in our universe, unless most of those future years were dead and lifeless, perhaps due to “entropy” or some other concept I do not understand.

So cheer up. Even if you only live 100 years, you haven’t missed all that much in subjective terms. Indeed, even a child that dies tragically at age 10 has experienced perhaps half of all that makes human life worth living. (The actual tragedy is for the child’s parents.)

Rudyard Kipling lived the biblical three score and ten years. In the final year of his life, he began an autobiography that was never completed. Chapter 1 starts with a quotation:

Give me the first six years of a child’s life and you can have the rest.

The chapter describes his childhood in India, and ends with this paragraph:

These experiences were a soaking in colour and design with, above all, the proper Museum smell; and it stayed with me. By the end of that long holiday I understood that my Mother had written verses, that my Father wrote things also; that books and pictures were among the most important affairs in the world; that I could read as much as I chose and ask the meaning of things from any one I met. I had found out, too, that one could take pen and set down what one thought, and that nobody accused one of showing off by so doing. I read a good deal; Sidonia the Sorceress; Emerson’s poems; and Bret Harte’s stories; and I learned all sorts of verses for the pleasure of repeating them to myself in bed.

RL Stevenson lived only 44 years, but his life seems equally complete as Kipling’s. Don’t fret about life extension, you’ve already absorbed everything that really matters.