A multiplanet enthusiast

 kw: book reviews, nonfiction, emigration, planets, mars

From time to time I use a very small prompt with an art generation program. The prompt for this image was "Planets everywhere." The site I used was Leonardo AI with the Lightning engine and its Dynamic style. The engine clearly doesn't understand either physics or astronomy. Actually, the way these programs work, the engine cannot be said to "understand" at all. But I like the surreal look of the image.

I produced this image about a year ago. It came to mind when I saw the cover art for Out of This World and Into the Next: A Physicist's Guide to Space Exploration by Adriana Marais. The author is based in South Africa, and she was one of the Mars One candidates for their plans to send people on a one-way trip. Mars One went out of business in 2019, but the banner has been taken up by Elon Musk and SpaceX.

The book is rather big; it's intended to be comprehensive, a sort of "History of humanity starting from the Big Bang." In keeping with the author's Germanic heritage, the Table of Contents is a thorough outline. Denying the trace of Teutonic detail-mindedness found in my own heritage, I'll touch a few items of interest and leave the rest to the interested reader.

The subjects of Part I, "Where do we come from?", remind me of a Bible verse. The three subjects (elaborated in 13 subchapters) are "The Universe", "Our biosphere", and "Are we alone?" Zechariah 12:1 tells that God "stretched out the heavens, laid the foundations of the earth, and formed the spirit of man within him." Each set of 4-5 items goes from broad to narrow. The tip of the arrow at the end of this Part introduces the Kardashev Scale. This is worth a bit of discussion.

Nikolai Kardashev proposed a three-point scale to describe the energy made available to a technological civilization:

1. A Type 1 civilization, labeled Planetary, has attained control of all the energy available on a single planet, including all the incident sunlight.
2. A Type 2 civilization, labeled Stellar, captures and uses all the energy output of one star, presumably its home star.
3. A Type 3 civilization, labeled Galactic, controls all the energy of its home galaxy.

Many, myself included, add Type 0, to represent the beginning of technology as evidenced by the first mastery of fire. This level was apparently achieved before Homo sapiens arrived on the scene, as much as two million years ago. How far have humans come towards becoming a full Type 1 civilization? Relevant facts:

• Worldwide energy use is about 625 exajoules per year (note: 80% is fossil fuel use). That's 174 billion megawatt-hours (MWh, = 1,000 kWh) per year.
• Solar energy influx is 1.53 million billion MWh per year. The ratio of these two numbers is about 1:8,800. In other words, our global energy use is 0.0114% of the energy available in sunlight.
• Internal heat flow of the earth, half radiogenic and half primordial, is 410 billion MWh per year. Thus total geothermal energy is about 2.4 times the global energy budget.

Thus we are about 1/90th of a percent along the way to being a Kardashev Type 1 civilization. Dr. Marais points out that photosynthesis converts just under 2% of sunlight into sugar, putting the biosphere's Kardashev level about ninety times farther along, compared with vaunted human technology.

Years ago I first examined the "carbon debt" indicated by the oxygen in the atmosphere and the oxidized iron in Earth's crust. Going back to the origin of oxygen-emitting photosynthesis (which came along half a billion to a billion years after other varieties of photosynthesis such that found in sulfur-digesting bacteria), we first find about a billion years of accumulation of "red beds" and other iron oxide deposits. Once the iron was all oxidized, oxygen began to accumulate in the atmosphere, as carbon-containing detritus was buried in the crust and later subducted beneath it by plate tectonics. I concluded that if we could find all the oil, natural gas, coal and tar in the crust, and also the graphite and diamond in the upper mantle, and burn it, that might use up most of the oxygen in the atmosphere. By contrast, 200+ years of fossil fuel consumption have "used up" about 0.01% of it. 

A little thought is sufficient to realize that there are limits to the energy available from fossil fuels, and not just because the oxygen will run out (to be replaced by carbon dioxide). Rather, we must consider the medical fact that humans (and who knows how many other animals) begin to feel distressed when the amount of carbon dioxide in the atmosphere exceeds 1,000 ppm. So, we don't want to go anywhere near that! From the vantage point of 430 ppm today, up from 280 ppm prior to the Industrial Revolution, 1,000 ppm seems far, far off. It isn't. Global energy use is still increasing, fast. Think about that.

A final point. I have seen it proclaimed that human civilization today is approaching a Kardashev level of 1; estimates range up to 0.7. Hmph! We are far below that. Just focusing on Kardashev levels zero and 1, we can consider a logarithmic scale, so that a scale value of 0.7 would represent energy use of about half of total solar input, or 765 quadrillion kWh per year. That's about 4,400 times as much energy as we are presently using! We need a different scale for energy consumption less than 0.1 of the solar value (the logarithm of 0.1 is -1, and starting from 1 for "1 solar output", the result is a Kardashev level of 0). For the moment, I'll set this aside.

As for levels 2 and 3, I have a couple of thoughts. A spherical construction that encloses the entire Sun at a suitable distance (probably between Earth and Mars) could capture all of the Sun's energy. Such a construction is called a Dyson Sphere, after the physicist who popularized the concept. We would need to take apart at least all of Jupiter and possibly Saturn also to accomplish it. Communication is a bit of a problem; the travel time of light or radio across the sphere would take about twenty minutes, one-way. Communication in a Galactic civilization is another thing entirely; getting a signal across the Milky Way Galaxy would require about 100,000 years. Talking across dwarf galaxies such as the Magellanic Clouds would be quicker; only a few thousand years!

In Part II, "Who are we?", the focus at the culmination of the 15 chapters is Terraforming. The next-to-last topic is "The Anthropocene," a designation that some have proposed for a geologic age that began 250-300 years ago with the Industrial Revolution, and so far has resulted in the extinction of many species (though it is so far probably less than one percent). Can we indeed terraform Mars? Let us contrast this with our current activities, which could be considered "the anti-terraforming of Earth" (my coinage).

It is worthwhile to ask, does our experience of human nature give us any grounds for optimism that we can properly terraform another planet? It is wise at this point to jump to the conclusion in Part III (Where are we going?), its last section, "Transforming our world." That is the crux of the matter. Can we terraform Earth? This is a question asked by astrophysicist Neil deGrasse Tyson: Which will cost less, establishing one (or a few) million people in a new colony on Mars, or restoring the environment on Earth so that future global catastrophes will not wipe us off the planet? Clearly, he is in favor of the latter course, and I agree.

I hope Dr. Marais gets her chance to go to Mars. She wants it so much she can taste it. Her evocative essay "Off-World" almost gives us the taste for it. It is markedly utopian. She needs to add to her scientific perspective the lens of history. No utopian society has ever succeeded. The advice of a pioneer of space inhabitation, "Go with friends!", tells you only part of what you need to know. Because friends change. Those who once ran together grow apart. The current divorce rate of about 50% does not bode well for the ability of mere humans to establish the kind of society she describes.

I like the dream. I wish I could conclude it won't turn into a nightmare.

Preparing to write this, I ran the prompt "Planets everywhere" in OpenArt's DynaVision engine, with AI Enhancement turned on. This was the result. The physics is a little better, but this is still surreal. If you were to see this density of planets in the sky, it would be best to go far away. The chaotic gravitational regime would soon prove catastrophic. Still, it's a fun image.

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A couple of minor errata:

• On p. 188 Yuri Gagarin is said to have "experience[d] the weightlessness of being beyond Earth's gravitational field." Not even close. He was well within it, but orbiting such that the centripetal force and the gravitational force exactly canceled. He experienced microgravity. If he'd been paying attention, he might have noticed very slight tidal forces tending to reorient him if he tried to float free inside his capsule.
• On p. 195 we read that the wavelengths of visible light are "similar to the size of atoms". The wavelength range of visible light is 400 nm to 700 nm, or roughly half a micrometer. The diameter of a typical atom is 2-3 tenths of a nanometer, or some 2,000 times smaller. The author is making the point that light bounces off material stuff. Actually, X-rays of the sort used in medicine do have wavelengths similar to the size of atoms, and they pass right through most materials. So the physics is wrong anyway.