The Amalgam is a galaxy-wide conglomerate of intelligent species that have the technology to scan their brains; it turns up in several of Greg Egan's short stories ("Glory" and "Riding the Crocodile") and in his novel Incandescence.

This enables them to have back-ups and to travel by information transmission at the speed of light.

Everyone lives peacefully, the technology enables an open society with plenty of freedom for everyone. Strangers are welcomed on any planet.

The individual humans in the stories live until they do not want to continue which is about 10,000 years in subjective time.

The problem is that they have not given up on physical bodies and that they also have children. This issue is not expanded further in the stories, but it is rather unlikely that a human being will only have two children in 10,000 years on average, so exponential population growth should eventually destroy The Amalgam, technology notwithstanding.

Is there anything that I have overlooked or is the Amalgam indeed inconsistent in this respect?

3 Answers 3


Egan tends to make a couple of assertions about advanced cultures, one of which is that among civilized people, exponential growth is considered uncouth. As far as I know, he has never described exactly how the greater society deals with the rare iconoclasts who like to double their numbers every twenty years, but we just don't see any such clades in the Amalgam.

There have been exceptions in some of his other works, when people increase their numbers without limit when they can also increase their resources without limit, but that usually hints at an Aesop about unlimited greed, as in Permutation City.

(In Vitals, Greg Bear draws a nice parallel between individuals who want to live forever, and cancerous cells: they gobble up lots of resources, multiply all they want, don't contribute much and don't really have a viable long-term plan -- even if they think they do.)


Egan starts from the observation that there's a finite amount of available energy in the universe, and hence a finite amount of computation that will be able to take place. So exponential growth must come to an end: if not voluntarily abandoned, it will come up against a physical limit to growth fairly soon. The only question is what the eventual steady state will look like: a co-operative sharing-out of the universe's resources, a destructive tooth-and-claw battle over them, or some mix of the two, in different regions of space and time?

These facts will be obvious to all intelligent and well-informed beings, and in the Amalgam stories Egan chooses to write about a co-operative galactic society. The actual mechanism by which this co-operation is achieved is not really the point of the stories: no doubt as with any kind of collective action problem it has to be approached by a combination of education, enforcement and engineering.

You can explore Egan's views in detail by reading this Usenet debate from 2007, in which Egan argues with a couple of people who consider the co-operative steady state to be not just difficult to achieve but impossible due to Darwinian natural selection.

Egan knows that something like the Amalgam is far from the only possibility:

Periods of stability, periods of change, periods of expansion, periods of non-expansion, can all have their place, and can all co-exist. The only thing that is likely to be physically impossible is endless exponential growth.

But he is optimistic:

I expect an intelligent post-human society to be aware of this high school mathematics, and to have noticed that needing something the universe can't give them—exponential growth—is a really dumb strategy. I expect they will be smart enough to realise that writing extremely efficient software is a far better use of their time and energy than acquiring new computational resources at the absolute maximum physically possible rate.


I've never read the stories in the topic, but from your question it sounds like a large number of the people would be in electronic form at any given time, traveling through space between planets. Even at the speed of light it would take approximately 4.5 years to get from Earth to the next nearest star system, assuming there was a colony there or some other reason to visit it. To visit planets near the galactic core (starting from Earth) it would take about 27,000±1,000 years traveling at light speed. Roughly double that to visit the opposite rim of the galaxy.

If the author of the stories present a [near] instantaneous method of transmission between planets then this answer is moot.

  • They do travel at the speed of light (although the galactic core is not part of the amalgam which is a major point of the story), but this only delays the inevitable.
    – Phira
    Jun 2, 2011 at 21:25
  • @user9325 Again, as I have not read the stories I an using supposition, but since people can be downloaded into a computer, how many "living" people are existing in a physical body at one time. Perhaps most people exist in digital form for the majority of their life (when not star traveling)? This would greatly reduce the space each person would require.
    – Xantec
    Jun 2, 2011 at 21:30

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