I recently read the Ringworld series by Larry Niven, and I was most intrigued by the Puppeteers. In particular, was the claim that their homeworld could do just about anything, except for get rid of the excess heat. Is this a valid claim?

To add in a few more details, the Puppeteer home world has been able to filter any pollution, create light, etc, but they have a problem in that they can't remove the heat that they generate. It has caused them to move to the very outer part of their solar system, so they have minimal sunlight, and even then, their planet is warming up. For more details as to the claim, see the Pierson's Puppeteers Wikipedia article.

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    It has been a while since most of us have read this series. Can you summarize exactly what you are talking about?
    – DampeS8N
    Feb 1, 2011 at 14:31
  • Do you mean you don't understand how they can be sooo brilliant and yet not able to cope with heating problems ?
    – Riduidel
    Feb 1, 2011 at 14:36
  • @Riduidel: Well, pretty much, yeah. Or is there some fundamental problem with heat that leads it not being a solvable problem? Feb 1, 2011 at 14:38
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    @Riduidel: no one can't beat thermodynamics, not even Pupetteers :( Feb 2, 2011 at 1:03
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    @TGnat - No, this is correct; waste heat was a problem on the homeworld well before the Puppeteers knew about the core explosion. (It's mentioned in Ringworld.) Aug 2, 2011 at 0:20

8 Answers 8


First, for those who don't remember Ringworld, the Puppeteers' homeworld has been detached from its sun altogether, and is migrating to one of the Magellanic clouds at STL speeds (Puppeteers don't trust hyperdrive) in order to escape from the explosion of the galactic core (which was discovered for them by Beowulf Shaeffer a couple of hundred years earlier).

But before that, it had already been moved to 1/10 of a light year from its star, because of problems with excess heat. (And its sun had subsequently become a red giant, which is why no human could find the Puppeteer homeworld -- they were looking for the wrong kind of star.)

So let's look at some numbers. The Earth receives about 5.5 yottajoules (YJ) of energy per year from the sun -- 5.5 * 10E24 joules. Fusion of two protons yields 6.7 * 10E-14 joules. So to generate as much heat from fusion as we get from the sun would require us to fuse around 10E38 protons. Which sounds like a lot, but there are 6 * 10E23 hydrogen atoms per gramme of hydrogen, so we'd only need to fuse a bit over 10E14 grammes of hydrogen. That's 100 million tonnes, or the amount of hydrogen you'd get from an 800 metre cube of water. The Earth has about 1.5 billion cubic kilometres of water, so if the Puppeteer homeworld is similar to Earth, then they can last for over two billion years at an energy output that's more than enough to heat the planet up even in the absence of a sun.

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    +1 for some awesome physics and math in the sci-fi Q&A
    – JYelton
    Feb 1, 2011 at 20:28
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    For clarity, those 1.5 billion cubic kilometers Mike mentions, are the one true billions: 1.5*10^12. Feb 2, 2011 at 1:00
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    Although the OP accepted your answer, I am at a loss understanding how it answers the question. The question asks why the Puppeteers can't get rid of excess heat and you're saying how they would be able to add more heat if needed.
    – Xantec
    May 3, 2016 at 20:51
  • Did you mean to say "fusion of four protons"?
    – Spencer
    Jan 10, 2020 at 23:35

The problem with Hearth's climate was not so much the stellar input, but the waste heat generated by the puppeteer's huge industrial base. The stellar input was 'easily' solved by moving the entire planet into interstellar space, but the industry problem was unavoidable. They must have scrubbed the atmosphere of all greenhouse gases to maximize the amount of long-wave IR the planet could emit, but I don't recall seeing that mentioned.


With respect to Niven, I don't think this is a valid claim. There's too much technology in Known Space for dumping planetary waste heat to be a serious problem.

In one of the Peace Corben stories, "War and Peace", the kzin Buckminster suggests using transfer booths to take hot gases from the surface of Plateau and dump them into local space for refrigeration. Cooled, the gases would fall back to the planet. Massively scaled up, a project like this could cool the surface of the planet to habitable levels after a few centuries. Start with a planet whose surface isn't a furnace already and such cooling could maintain the climate indefinitely. The Puppeteers would use stepping discs instead of transfer booths, but the principle is the same.

Sinclair time compression fields could also be used to shift long wave IR up to higher frequencies where it could be more efficiently radiated away. Stepping disc technology would be useful here as well, as the discs have been shown capable of passing electromagnetic radiation as well as matter. So instead of pumping UV (frequency shifted long IR) through your atmosphere out to space, you pump it directly to space via stepping discs.

Alternately, just wrap the whole planet in a Sinclair field to cool it 512 times faster, as Harrington's characters did in "Heritage". Stasis fields can't be operated on the planet while this is going on, but (as far as we know) everything else could proceed normally.


From what I gather, you mean dealing with a run-away greenhouse effect. Presumably in light of all their other technology, how could they not be able to deal with it?

It really depends on just exactly how they were able to do things like move planets around to form the Rosette. Something I don't remember ever being explained.

Still, there really is no magic here. So you would have to capture the excess greenhouse gases, vent them off into space and replace them, or vent off the heat itself. I'd say it is plausible, depending on what other technology they have. And if I remember correctly, they acquire FTL travel the same way all the other species do in that universe. From external sources. So they may never have progressed to the point of having such high technology as to be able to capture the gasses creating the greenhouse.

They are traders, after all. They may have gained all their high technology through reverse-engineering and purchases in a short time. Maybe the easiest way to deal with the problem was they way they did. Rather than creating new technology to deal with the underlying issue.

  • Not run-away greenhouse effect so much as the body-heat and incidental heat of circa a trillion warm-blooded sentient beings of about human mass and metabolism. I believe that civil engineers used to figure you need about 140 W of cooling per person in an office setting just from body heat... Feb 1, 2011 at 20:49

It does seem like a flaw. In Ringworld Throne Louis Wu uses the superconducting fabric to build a heat dispersion suit, so he can survive Teela Brown.

He also dumped the end of a superconducting cable into the lake to dump the excess heat.

Seems like the Puppeteers ought to be able to build a heat pipe to radiate it out into space.

And he used it another time in the book, I remember hanging it from his ship maybe?

  • Puppeteer might judge a beanstalk too risky. Feb 3, 2011 at 0:04
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    Radiation doesn't cool things very efficiently when you're dealing with terrestrial heat levels. Feb 1, 2012 at 20:13
  • These events were in The Ringworld Engineers, not Ringworld Throne.
    – Brady Gilg
    Jul 8, 2021 at 20:07

I'm not a physicist so the details may be shaky, but I think this correctly describes the situation:

A highly technological society with a large industrial base is going to produce and use up a lot of energy as part of its daily existence.

Even assuming maximal efficiency throughout, and devices in place to reuse as much of the waste energy as is possible, there is a theoretical limit beyond which it's not possible to improve efficiency or recover energy. Check out Carnot's theorem for an idea.

Due to conversion costs, it's most likely that unusable, unrecoverable energy will end up radiated as heat. It's cheaper to convert energy into heat energy, than to go back, especially if you're looking at an already hot planet.

So it's entirely reasonable that a very efficient, highly optimized society, will be producing high quantities of excess heat.

This is not a problem, yet. It's actually, in general, easier to be energy efficient - especially for mechanical processes - at higher temperatures. Hotter engines are more efficient - mostly since their environment can't absorb as much waste if it's warmer. The real problems with heat are for survival of living organisms, and for proper functioning of advanced tech devices - the more advanced they are, the more likely they to be sensitive to energy differences. Look at your computer internals as an example.

So, if I had to guess, the puppeteers, despite being as energy efficient as possible, produced too much heat that the balance between efficiency and function was skewed, and they had to take extreme measures to dispose of the excess.


I'm not convinced you couldn't use heat pumps to pump heat to heat radiators. This just requires that you have nearly unlimited power to deal with. It would be expensive, but doable. Alternatively if your population was confined to a few domed cities, they could be airconditioned, and the rest of the planet could be hundreds of degrees Centigrade. That would increase the amount of waste heat your planet gives off by maybe ten to a hundred times. Its still limited, but could be quite high.

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    The problem is, there was a trillion people on the planet, which would make it rather difficult to only have a few domed cities... Feb 2, 2011 at 18:47

Yes I agree with Kyle Jones!

I think there is way to many technology to not solve this problem even in a citizen way. What I think would be the easiest way would be stepping disks, since they use them for everything else why not that too? And Have a radiator fin sticking into an ocean or grid of superconductor cables, then have the fin half sticking out another side of a disk in space?

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