This Island Earth

I finally finished Neal Stevenson's Seveneves, a monumental end-of-the-world novel. I tend to "read" this kind of book as an audiobook while driving, which means it takes a while to get through one of this length.
Seveneves begins with the moon blowing up, although as many reviewers have pointed out, this isn't a spoiler since it is the first sentence in the book. On the other hand, there will be some spoilers here, so I urge you to read the book first.

As I started to listen to the story, once it became apparent that the moon was going to continue to break up and ultimately produce a "hard rain" of meteors that deposit enough energy in the atmosphere (and surface) that it would glow red hot--and it does glow red hot in the story-- I realized I had seen it before. One of the more visually spectacular (if scientifically dodgy) SF movies of the 50s, This Island Earth, has the planet Metaluna being attacked by forces which use meteors as weapons, and in the movie, you see the attack succeed, the rain of meteors overwhelm the defenders' forcefields, and ... yep, the planet glowing red hot as the aliens finish it off.

(Oh, and as long as we're on 50s SF, the parallels to When Worlds Collide where there is a frantic rush to build rockets to escape the doomed Earth with a remnant of humanity is too obvious to mention.  So I won't.)

This is not a review of Seveneves -- that would take a year to write properly -- but just an investigation of one point. Namely, does that really work? Could a meteor bombardment make a planet glow red hot, and if so for how long? In the story, it is some appreciable fraction of 5000 years.

We are used to vast energies in our weather system dwarfing what mere puny humans can do with our our little machines. But all of that energy is just side effects of the incoming sunlight on its way to being re-emitted as IR. For the planet as a whole, that energy flux works out to about 300 watts per square meter (and in equals out to within roughly a tenth of a percent).

For the entire planet to glow red hot, it would have to be about 1000 degrees Kelvin, and it would radiate a LOT more energy into space. To do the calculation right, it gets complicated, in lots of ways, so what I'm about to do is an extreme simplification. But for a back of the envelope, the average temperature of the earth now is about 288 K. Planck's Law says black-body radiated power scales as the cube of the temperature, so the red-hot Earth would be radiating about 40 times as much as now, i.e. 12 kilowatts per square meter. Earth is about 5e14 m^2, so it would be putting out 6e18 watts.

One kilogram at the height of the moon's orbit has a potential energy relative to the surface a little over 60 megajoules (the kinetic energy of its 1 km/sec orbital velocity is just half a megajoule). Thus you need to drop 1e11 kg of moon per second on the earth to keep it red hot. The moon masses 7e22 kg, so you get 7e11 seconds of bombardment if you want to keep the Earth red hot.

7e11 seconds is 22,000 years; so yes, it works. You need to use less than a quarter of the moon.

The Age of BiV

Robin Hanson and Bryan Caplan are having a cross-blog debate, or at least discussion, about Robin's book Age of Em. Without going into the specifics, I get the feeling that there is a certain disconnect right from the start.
Robin thinks that the em world will develop so quickly, and contain so many people compared to the outside meatspace world that we can treat the latter as static and uninteresting; and besides, the em world is what the book is about!
Bryan on the other hand finds it hard to think of the ems as people at all. After all, they are just computer programs interacting through software; the whole em world is just one big video game. The real people are the ones on the outside.

Allow me to propose a scenario which I think has at least a chance of engaging both points of view. Let's assume a level of technology roughly equivalent to that in Age of Em, i.e. the ability to scan a brain down to a level where you have captured all the essential detail. Below this level we will assume that we have studied the structure of neurons etc in general all the way down to the molecular level. But we will also assume that we have a fabrication ability to match. So when we have scanned a brain, we will simply rebuild it, molecule by molecule.
What do we do with such a brain? Why, we put it in a vat, of course, and let it think. We put the vat (it's only 1.5 liters) in a giant factory-like building along with lots of pipes and pumps and tanks of nutrient fluid, and enough computing hardware to run a virtual world simulation for each brain. Note that the level of understanding of our neural circuitry (and amount of computation) necessary is just the same as in Robin's em world.
Now are these BiVs ("Brain in a Vat") really people? After all, we could instead of copying them molecule for molecule, simply have taken actual human brains and put them in the same BiViac (sorry). Furthermore, we now have a situation on which philosophers from Descartes to Bishop Berkeley have weighed in for centuries. BiVs think; therefore they are.

The BiV world has many, but not all, of the features of Robin's em one. A reasonable level of nanotech lets you build a brain in well under an hour. One obvious place to get the material is deconstructing a previous brain, copying off a record of its fine structure if you care to. Everbody gets to live in a fantastically splendiferous virtual world, shared or not at their whim. You can teleport, you can fly, you can have a city with a million flying cars and no traffic worries, because the cars simply go through each other.
The big difference would be the lack of a brain-speed control knob.

How are we to measure the income and wealth of a BiV? Each one can have, to all apparent physical purposes, anything he wants. In the real physical world, all he needs is a fixed supply of "juice" (under which rubric we will include both nutrients and electricity for the VR system, pumps, etc). "Fixed" is the operative word; in some sense it is not possible to make him any better off, physically, than he is at a "subsistence" level.

What is subsistence level? One easy way to guess is the energy input, some of which is direct power and some of which gets backed out into the manufacturing process for the nutrients. Grand total for a full human body is 100 watts; nanotech manufacturing brings the capital cost down to a level we can ignore for the moment. So the BiV at current typical power prices needs 24 cents per day, or less than $100 per year.

So that's subsistence, in a virtual world of limitless luxury. The main reason a BiV would want more money would be prestige, status, to have things others didn't that were only valuable because they were rare, and things in the real world. So he might work hard for that, if he were ambitious. But given that people need so little for the baseline, it's hard to imagine how they could be so unproductive as to have to work more than a few days a year if they didn't want to.

The average American (including children, the elderly, etc) produces nearly 500 times as much in economic value than the BiV subsistence. If we start with a selection of motivated, intelligent people, one can guess that they would be at least 5 times as productive on average. A factor of 2500 is a long way to fall in productivity, even if most BiVs spent most of their time sending pictures of cats to each other.

On the other hand, one can sink a virtually infinite amount of time into software. A large part of the internal effort in a BiV (or em, for that matter) world would be spiffying and decorating the virtual worlds, which would do nothing as seen from the outside in the real world. I think that the real question in either formulation would be how much of the effort went into really useful productivity enhancement tools, and thus tended to counteract the diminishing returns to adding more brains.

Back to School

Everybody and his dog Astro in the futurist world seems to be writing a review of Robin Hanson's book Age of Em these days, so I thought another one might be an appropriate opening post.
As I assume most of the readers who find their way here already know, the book is an analysis using standard social science results of a very carefully selected possible part of a possible future, namely a city full of uploaded human minds interacting through a simulated virtual reality.
My own thoughts on such a scenario, such as they were, appeared in Nanofuture about ten years ago:

 Uploading offers another way into a bigger world. As wide-open as the physical possibilities are with nanotechnology, they are wider still uploaded. The current-day philosopher asks, "What is it like to be a bat?" but the upload could know. We could have new senses, not merely mapped onto our current set, and new forms of intuition, maybe even new emotions, more appropriate to the world we live in.  I mentioned before how our present artificial environment has outstripped our native equipment evolved on the African savanna; how much more will the world of tomorrow?
You must not think of such a world as over-complex and confusing. It would be to us, but so would our world be confusing to Homo Erectus. In fact, our descendants (and with a little luck, maybe even ourselves) will be more naturally comfortable, and understand their environment more intuitively, than we do ours today. That's because we've jacked up the complexity of our current world, but not the equipment we use to understand it; they will be able to do both.
Where does personal responsibility and independence go when people are programs running on the same ultra-megacomputer? Perhaps surprisingly, the range of options is the same, or perhaps even wider, than in the physical world. Let's consider a few cases, as widely scattered signposts to the vast terrain of possibilities.
There could be the equivalent of a processor per person, with communications channels between them, and one or more complex environment simulations for them to interact in. This would correspond to people with separate brains in the real world. This level of integration would interact well with real humans and people running on physically separate robot processors. The assumption here is that your thoughts are entirely yours, and that you could own a part of the physical world or simulated environment over which you would exert more or less exclusive control.
In a software world, it will be possible to create the equivalent of germs, fleas, lice, and ticks--the descendants of computer viruses--simply by thinking about them. The temptation will be great for the community to want to control your thoughts in fear of such things, even though people who did that would be as rare as people who deliberately spread disease today.
This is a significant concern because lowering the firewalls between people will have so many advantages in other ways. Exactly the same kinds of thing happened to people when they began living in cities: disease was a scourge, and epidemics like the Black Death could wipe out a third of the population. Yet people crowded into cities because it greatly facilitated communication and trade, the building of common infrastructure, and other economies of scale. And yes, there were plagues; but the advantages (usually) outweighed them. Indeed, living in such cities clearly made people stronger and more effective in the long run.
In the physical world, technology has helped finesse the issue, with transportation, sanitation, medicine, and so forth. Nanotechnology can carry that further, for example with skinsuits acting as biological firewalls but allowing direct personal contact. In the software world, the choices are harder. Uploading will allow things like direct transfer of thoughts and emotions, joint experience, and many modes of interaction as yet unthought-of. It will also allow not only direct monitoring of people's thoughts, but legislated changes in the structure of their minds. Given the track record of bureaucracies in the real world, the clear and present danger is that communities of uploads would quickly evolve into soulless monstrosities.
Luckily, soulless monstrosities won't win in the long run. They just can't seem to "play nice" with other soulless monstrosities. Evolution could have taken us that way, like ants, but didn't. There's too much value in the adaptable flexibility of the semiautonomous intelligence that we are. One of the challenges awaiting us as we move forward is to understand this well enough to avoid some unfortunate experiments.
With a properly defined Bill of Mental Rights, however, an upload community could be a truly marvelous place. It would be like the concentration of talent of a Hollywood or Silicon Valley--centers of great creativity and an enormous value to humanity as a whole.

 Robin's scenario precludes some of these concerns by being very specific to a single possibility: that we have the technology to copy off any single particular human brain, we don't understand them well enough to modify them arbitrarily. Thus they have to operated in a virtual reality that is reasonably close to a simulated physical world.
There is a good reason for doing it this way, of course: that's the only uploading scenario in which all the social science studies and papers and results and so forth can be assumed to still apply. Any other scenario, and you'd have to examine a lot of assumptions on a case-by case basis.
But it also allows a different kind of analysis, which I don't remember Robin doing in quite this way in the book: We can examine the question "What is it like to be an Em?", in the same spirit as the philosopher Nagel and his bat. And, again because of the assumptions, you can do this by pretending that you, the Em, are living in an actual, comprehensible, physical world.
There was a Star Trek episode ("A Taste of Armageddon") in which there was a planet whose highly advanced civilization featured disintegration chambers -- people walked in, and nobody walked out. The Em world would have these, but with a second control button: someone walks in, and identical twins walk out.
Furthermore, the process is, again by Robin's explicit assumption, inexpensive. Now I estimate that in current computing technology the amount of hardware it would take to run a human-level AI will cost a million dollars. But with the assumptions that we don't understand how it works and thus can't optimize it, and thus have to run a direct copy simulation at a fairly low level, you might reasonably be talking about orders of magnitude more computer to run a human mind.
Yes, we'll probably get there, with Moore's Law. But the take-away implication is that in the Em world, processing power will be very, very cheap.
What that means is to an Em, things are very cheap. Everything in the Em world is part of a simulated VR; any object is just a piece of software. An Em can create or copy giant machines, tropical islands, great cities (minus the people), and probably Mars-like planets with the wave of a hand. "What it would be like" is like living in a Utility Fog world. The hardest part of creating virtually anything would be deciding and describing what you wanted.
Another salient aspect to Robin's Em world is his original economic insight that if people are cheap to copy (and the process is fast), they would induce a Malthusian dynamic and wages would tend down toward subsistence level. Furthermore, the people selected for uploading will be highly intelligent and motivated.
Now where have you ever lived where there were lots of creative, intelligent people, many just like you, doing remarkable wonderful things with big expensive toys (some of which you designed!), but you only got, personally, subsistence wages for it?
Yep, you got it. Graduate school. What it is like to be an Em is ... a graduate student.