Microcenturies, Methuselahs and Musks: 35 new ways to measure time

The Long-termist's Field Guide: 1,000 Ideas For The Next 1,000 Years

You’re reading The Long-termist’s Field Guide, a newsletter about long-term thinking. This month’s edition is about units of time that you may not have heard of - from Methuselahs to Musks.

Around a decade ago, when I was a feature editor at New Scientist, I worked on a special issue called The Deep Future: A Guide to Humanity’s Next 100,000 Years. As part of that, I spent an afternoon with paper, pen and a calculator to calculate an infographic that spread across ~10-12 pages. It depicted a timeline of 100,000 years, but used the unit of human lifespans.

Our graphics editor placed little people in a line so that as you flicked through the magazine, you could see how many lifespans you were away from the year 102,012. It was fun to do, but I don’t think we nailed it. It showed how big 100,000 years is, but the goal was actually to do the opposite: make deep time feel more personal using a different unit.

Since then, I’ve often wondered: how might the units we use to describe time affect how we think about it? Consider a millennium. You can describe it as 10 centuries, but you can also say it’s 13.7 lifespans (global average), or roughly 30-50 generations. To me, the latter two make the year 3021 feel closer. What I particularly like about the unit of generations is that it situates you and your relatives in the timeline. (The downside is that it’s fuzzily defined, varying between 20-30 years.)

Might there be other units of time we could start using, instead of the obvious? Recently I stumbled on a terrific wikipedia list page of “humorous units of measurement” that offers some inspiration.

Here are a few entries from the section on time:

Microcentury - The mathematician John von Neumann used the term microcentury to denote the maximum length of a lecture. One microcentury is 52 minutes and 35.7 seconds – one millionth of a century.

Nanocentury - A unit sometimes used in computing… coined by IBM in 1969 from the design objective "never to let the user wait more than a few nanocenturies for a response". A nanocentury is one-billionth of a century or approximately 3.156 seconds.

New York Second - "the shortest unit of time in the multiverse" defined as the period of time between the traffic lights turning green and the cab behind one honking.

Onosecond - British YouTuber Tom Scott defines the onosecond as the second after one makes a terrible mistake, such as deleting the wrong file or sending a text message to the wrong person, where the person in question can do nothing but say "oh no".

So, could there be others, for longer periods of time? I’ve compiled a selection below - a mixture of real and hypothetical, serious and not-so serious. (Got suggestions you’d add? Let me know on social media or by reply!)

An Olympiad (four years) - a timely example to start, the period between Olympic Games. You could also measure in “World Cups”, or the “quadrenniums” that mark the leap-year gaps between each 29 February.

An Indiction (15 years) - used by the Romans for a tax cycle. A Circumtax, by contrast, is the length of time you believe you have before you need to get round to filing your taxes, and it is roughly five times the period you actually have.

A gigasecond (31.7 years) - a multiple of the SI unit. There’s also the terasecond (31,700 years), the petasecond (31.7 million years) and so on through exa, zeta, yotta up to 31.7 quadrillion years. You can do the same for years, so a gigaannum is 1 billion years, for example. Someone once went to the trouble of calculating how these units line up with known dates – so for example, there have been 63.8 gigaseconds since the year 0CE, and we have about 5 gigaannums left until the Sun dies.


A Shake (10 nanoseconds) - a unit invented by the Manhattan project scientists, this describes “roughly the time it takes for one step in a nuclear chain reaction,” the researcher Anders Sandberg tells me. It comes from "two shakes of a lamb's tail", he explains. While the shake is too short to help us with long-term time, the atomic scientists’ use of idioms could offer inspiration (they also coined the unit of area “Barn” based on the expression about hitting one). So, how about a Blue Moon (2-3 years)? Or if you’re British, a Yonk (3 years and 13 days, apparently) or a Donkey’s Year, which is less than a human lifetime, but outside recent memory, so >15 years?

A Gladwell (10,000 hours) - or 417 days. A Badwell is the amount of time it takes before a bold claim in a popular non-fiction book is debunked.

A Jubilee (50 years) - originally a biblical term, a jubilee is a year of celebration, freedom and forgiveness: “Thou shalt sanctify the fiftieth year, and shalt proclaim remission to all the inhabitants of thy land: for it is the year of jubilee.” Nowadays it’s also associated with the Royal Family, marked from silver (25 years), through golden (50), up to diamond (60) and platinum (70).

A Prometheus or a Methuselah (5,000 years) - the names of two Great Basin bristlecone pines, which are (or were) the oldest known trees in the world. Sadly, Prometheus was unwittingly chopped down in 1964, but Methuselah is still here, now around 4,850 years old. I like this unit - it’s larger than a millennium, but relatable. If you wanted a shorter tree-based unit, you could also measure with a Redwood, which has an average age of 500-700 years (though many are older).

A Shoes On (~400 years) - the time it feels it takes between me asking my 8-year-old daughter to put her shoes on to go out, and her actually doing so.

A Neptunian Year (164.81 years) - the longest planetary orbital period in the Solar System. This could be just one of many astronomical possibilities. If we settle on the Red Planet, we’ll have to get used to talking about Martian Years (1.88 years), or if a certain billionaire conquers it, Musks.

Sandberg also highlights astronomical cycles from antiquity, which I’ve converted into units, such as a Meton (19 years), from the Metonic cycle, the Ancient Greek calculation of the time it takes for the solar year and the lunar months to synchronise. Or a Callipus (76 years), from the Callippic cycle.

For longer timeframes, there could be a Precession of the Equinoxes (26,000 years), based on the cyclic wobbling of Earth’s axis of rotation. Or a Galactic Year (230 million years) - the time it takes for the Sun to make a round trip around the Milky Way.

But for really, really long, you’ll need a Kalpa, proposed in Hindu and Buddhist cosmology. Bhāskara gave it as 4,320 million years,” says Sandberg, “but there are longer ones like the 3.11 trillion year one in Bhagavad-gītā. That later measure is roughly how long red dwarf stars will shine and hence how long the stelliferous era will be (it is likely a few such kalpas, maybe two or three).”

Finally, should you need a one-size-fits-all temporal unit, I might suggest A Teacher’s Five Minutes (undefined). My wife, who is a secondary school teacher, tells me this is the timespan given to a class to complete an exercise in peaceful silence. It is never five minutes, but is instead subjectively defined by the teacher as whatever time they want.

More long-termist mascots

Thank you to everyone who shared and replied to my last post about the living things that deserve to be “long-termist mascots”. Here’s a few new ones that people nominated:

The Wollemi Pine - “It evolved c.200 mya,” says David Farrier (@david_farrier). “Thought to have been extinct for millennia, living trees were found deep in NSW bush in 1994. In 2008 Wollemi seeds travelled to the International Space Station. From Gondwanaland to orbit!”

Bacterial bioluminescence - “It brought light to the deepest reaches of the ocean floors over 2 billion years ago. Bringing light through the ages,” says James Janson Young (@rubbersoul). (Check out Young’s new newsletter and youtube channel called Ours For The Making about how to become “future fit” in an age of short-term thinking.)

The 17-year cicada - “I set a calendar reminder for May 2038 for the next time Brood X appears,” says Josh Calder (@geofutures)

The Aldabra giant tortoise in the Seychelles - Lauren (@writevintage2)

The cockroach - because its “endlessly adaptable”, says Kate Cholewa (@katecac) or the giant squid because it “occupies a niche suited to few... and the niche remain constant over time with minimal interference.”

A very old patch of seagrass - Ricardo Reis (@KyriuRReis), who adds, “I would go for ecosystems… and not single species/individuals.”

Utah aspen grove - “It is 80,000 years old although no one tree is anywhere near that age,” says Jack Uldrich (@jackuldrich)

A humungous fungus - Bethany Brookshire (@beebrookshire) “NO ONE elected Armillaria! One in Oregon is more than 2,400 years old. How does it live so long? NETWORKING.”

Bacteria - “They evolve every few hours and go through millions of generations exchanging DNA horizontally and will outlive everything no matter what,” says Rene de Paula Jr (@renedepaula)

Gingko tree - “Equally at ease contemplating birds songs or truck fumes,” says Isaac Yuen (@ekostories), who shared a piece he wrote called “Life lessons from the odd and ancient” that also contains the coelacanth, tortoises, sharks, and red pandas.

Lichen - “Some are among the oldest living things, very slow growing, grow everywhere, quite common around the world,” says Tristan Ferne (@tristanf)

Tardigrades - “Obvious but hard to beat,” says Adam Proctor (@fortsunlight). “Extremely hardy (being able to retract into a near indestructible 'tun') and the cutest thing you'll see down a microscope when it's shuffling about on its wee legs.” He helpfully shares a picture from his days studying zoology:

Amnesia, concrete and galactic civilisation

I’ve been trying to write more (and faster!) recently. So finally here are a few articles I’ve produced over the last month or so, from a new piece of long-terminology called “generational amnesia” to an attempt to provide a longer view on the era of billionaire space travel:

Generational amnesia: The memory loss that harms the planet - As each new generation inherits the world, vital knowledge is forgotten.

Concrete: The material that’s ‘too vast to imagine’ - There is so much concrete in the world that soon it will outweigh all living matter – including us.

The long-term quest to build a galactic civilisation - Behind the headlines about billionaire jaunts into space, there's a deeper motivation – the belief that spreading into the cosmos will save humanity's future. How did this idea emerge?

Thanks very much for reading. Wishing you all the best for a pleasant and long-minded August.

Do let me know on social or by reply if you have extra suggestions for new temporal units! I’m @rifish on twitter and recently joined instagram as @thelongtermist.

best wishes



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