Have you ever had one of those mornings where you wonder where your get-up-and-go went? It takes a lot of energy to face the challenges of modern civilization. The difficulties facing humanity have differed over the millennia, but have always demanded a lot of energy expenditure.
Now, in a paper published in Astrobiology, astronomer Jacob Haqq-Misra at the Blue Marble Space Institute of Science in Seattle explains how it takes a lot of energy to sustain humans but also a whole lot more energy to prepare the necessary conditions and history of life to make human existence or any other conceivable intelligent physical life possible.1
Requirements for Complex Intelligent Life
The requirements for complex intelligent life are much more stringent than those for microbial life. For example, microbes do not need much, if any, atmospheric oxygen. Intelligent life needs it at a fine-tuned level—any less atmospheric oxygen would limit activity; any more would generate uncontrollable wildfires and would shorten the life spans of intelligent life. On Earth, it took 3.7 billion years for atmospheric oxygen to accumulate to a level conducive for intelligent life. It would have taken much longer if not for Earth’s being continuously packed with an enormous quantity of photosynthetic life.
Intelligent life also requires aggressive, long-lasting plate tectonics. Without such, the ratio of surface continents to oceans would either be too high or too low to sustain intelligent life. Geophysicists cannot conceive of the necessary ratio being achieved in less than 3.7 billion years.
Several biogeochemical cycles must be sustained at high levels for billions of years in order to compensate for the brightening of a planet’s host star. I have written about these cycles in previous blog posts.2
Host Star Constraints for Intelligent Life
Several life-critical chemical reactions require a fine-tuned level and spectral range of incident ultraviolet light from its host star.3 All the life requirements listed above also require a minimum energy flow from the planet’s host star. Haqq-Misra calculated that, for multicellular life to be possible, the planet must receive at the top of its atmosphere 1034 joules of energy in the spectrum range between 200 and 1,200 nanometers (2,000 to 12,000 angstroms).4
This energy requirement poses a problem for planets orbiting stars less massive than the Sun. The energy output of hydrogen-fusing stars (main sequence stars are the only possible candidates for hosting a life-harboring planet) is proportional to the 3.9 power of its mass. At 13.8 billion years old the universe is too young for any star less than 70 percent the Sun’s mass, regardless of when it formed, to have expended enough energy between 200 and 1,200 nanometers for animal life to exist on any of its planets.5
It was at this point of considering requirements for multicellular life that Haqq-Misra ceased his analysis. He concluded that planets orbiting stars less than 70 percent the Sun’s mass—which includes 80 percent of all existing stars—are noncandidates for hosting multicellular life.
For the equivalent of animal life and especially human life the constraints are more stringent. Stars that are birthed early in the universe’s history (the first 8 billion years) lack the heavy elements needed to form planets on which the equivalent of human beings could conceivably exist. Conservatively, stars less than 90 percent the Sun’s mass are eliminated as candidates.
What about stars more massive than the Sun? Such stars burn their nuclear fuel at much more rapid rates than the Sun. The faster a star fuses hydrogen into helium the brighter it becomes. Life cannot tolerate more than about a 2 percent increase in incident stellar radiation on the host planet’s surface. Over the 3.8-billion-year history of life on Earth, the Sun has brightened by a little more than 20 percent.6 Earth’s extremely efficient biogeochemical cycles have continuously removed greenhouse gases from the atmosphere at rates sufficient to compensate for the brightening of the Sun.7 Stars more massive than the Sun will brighten by a whole lot more than 20 percent over the course of 3.8 billion years. Any conceivable set of biogeochemical cycles will not be able to sufficiently compensate for such stars’ brightening.
The rare earth doctrine8 states that only planets virtually identical to Earth in its characteristics will be possible candidates to host complex life. Haqq-Misra’s research provides more evidence for the rare Sun doctrine—the idea that only stars virtually identical to the Sun will be possible candidates to host planets on which complex life could exist. The only plausible explanation for the rare Earth, rare Sun,9 rare Moon,10 rare planetary system,11 rare galaxy,12 rare galaxy cluster,13 and rare supercluster of galaxies14 is that a supernatural, super-intelligent, super-powerful Being purposely designed and manufactured all these things for the specific benefit and purpose of human beings.
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