Do not buy three decades of loo paper, nor depart today for Barnard’s Star

16.15, Tuesday 20 Dec 2022

Say you were flying to Barnard’s Star, 6 light years away. Should you set off today? Or are you better off waiting a century or two for starship technology to improve and leaving then?

In not-unrelated news: Ben Terrett, friend and appointed Royal Designer for Industry, recently revealed his fantasy of buying three decades of toilet paper in one go: If I won the lottery the first thing I’d do is buy enough toilet rolls and enough bin liners for the rest of my life.

First let’s think about how many you’d need of the rest of of your life. I’m 47 and the average life expectancy of a UK male is 80 years old. So I’ve got 33 years left to live. (That doesn’t sound like much tbh.)

The average UK household uses 100 toilet rolls a year so that’s 3,300 more toilet rolls. A hipster toilet roll like Who Gives A Crap costs £1 a roll so that’s £3,300. …

Maybe we should bite the bullet and do that now. Storage might be a problem. Hence the lottery win and I could buy a house with a room just for bog roll and bin bags like the Kardashians or something.

Also he says I thought I’d try and get all Matt Webb about this, which is a red rag to an etc.

Usually I would be in favour of this kind of brave domestic optimisation. (For years I’ve stacked up my paper post into giant piles and I batch-open every 6 months. It’s way more efficient and I barely ever get sent to collections nowadays.)


Back to Barnard’s Star.

(Barnard’s Star being the traditional destination to consider for speculative interstellar travel because of the 1978 engineering study, Project Daedalus, as previously discussed.)

There is something called the wait equation.

Current technology would allow us to reach Barnard’s Star in 12,000 years, setting off today.

Or: wait.

If technology growth is likely to double every 100 years the speed at which this journey could be made, then, using equation –1, it would seem that a voyager need only wait 690 years or so to make the journey in 100 years or less (i.e. at a speed of 6/100 speed of light). In other words, the star could be reached in well under a thousand years from now simply by waiting. Total time to destination is 690 years of wait + 100 years of travel = 790 years.

So don’t leave too early. Not only would it take longer, but early leavers will become latecomers, behind the wave of progress, those annoying historical curiosities, hardly at the forefront of social change … little to contribute … a thorn in the side of the authorities. (The anachronauts from Greg Egan’s Schild’s Ladder, if you’ve read that.)

But also don’t leave it too late: the journey time will keep dropping, but decreasingly, and after a certain point progress won’t help you overtake those who have the head start.

The sweet spot is what the wait equation is for. (It’s heavily dependent on economic growth rate assumptions.)

See Kennedy (2006) in the refs below. PDF available at that link. Further discussion at the blog Centauri Dreams: Barnard’s Star and the ‘Wait Equation’.


Got a long computer program to run? Why start now?

We show that, in the context of Moore’s Law, overall productivity can be increased for large enough computations by ‘slacking’ or waiting for some period of time before purchasing a computer and beginning the calculation.

Gottbrath et al (1999).

That paper via Ethan Mollick on Twitter, who also points out a related theory that aliens are quiet because they are… hibernating?… waiting for computers to get better?

In fact, this is basically one of resolutions to the Fermi Paradox: the Aestivation Hypothesis suggests all the powerful alien civilizations are merely sleeping between the stars until computing power becomes better. Ph’nglui mglw’nafh Cthulhu & all that.

The Aestivation Hypothesis!

Sandberg et al (2017). Both papers linked in the references below.

So, loo paper.

Imagine stocking up with a lifetime supply in the 1990s and then a few years later they invent the multi-ply quilted aloe vera rolls – and you can’t get any because you’ve got a whole room full of the thin scratchy stuff, you’ve got no room. And you can’t offload any to make room because nobody wants it; they can get the luxury paper for cheap-enough.

Or what if you’d had the misfortune to stock up in 1997 and your Kleenex was illegally embossed with Penrose tiles. No reselling without IP violations.

Toilet paper innovation barrels along. Less than a century ago: by 1930 toilet paper was finally manufactured ‘splinter free.’

Who only knows what it will be like in another decade or two.

At this point I should calculate the wait equation for loo paper given technological progress curves and opportunity cost of storage space and the utility function of wiping your bum and so on. I imagine there’s an optimum number of years to purchase in advance.

But anyway.

Buy as you go, probably.


  1. Kennedy, A. (2006). Interstellar Travel-The Wait Calculation and the Incentive Trap of Progress. Journal of the British Interplanetary Society, 59, 239-246.
  2. Gottbrath, C., Bailin, J., Meakin, C., Thompson, T., & Charfman, J. J. (1999). The Effects of Moore’s Law and Slacking on Large Computations. arXiv.
  3. Sandberg, A., Armstrong, S., & Cirkovic, M. M. (2017). That is not dead which can eternal lie: The aestivation hypothesis for resolving Fermi’s paradox. arXiv.
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