Your Turn, Round 2-1: Fermi Problems
In 1950, while sitting at lunch, Enrico Fermi is said to have asked “Where are they?“. Fermi liked to do order-of-magnitude physics, and had worked out that if intelligent life is common in the universe and can spread through space at a significant fraction of the speed of light, extraterrestrial intelligence should already be here. So, where are the aliens?
There are many proposed resolutions to this paradox. One is that there are very few places for life to evolve – the Rare Earth hypothesis. That becomes significantly less likely the more we know about extrasolar planets. At the same time, SETI has advanced to the point that we can say that there are no other Earth-like civilizations within a few tens of light-years of here and no Dyson Swarms within several thousand lightyears. So even if planets are common, perhaps life is not.
And even if life is common in the universe, perhaps intelligence is not often selected for. This may be contradicted by life on Earth, but it depends on the definition of intelligence. Apes are intelligent. Dolphins and whales are intelligent. Elephants are intelligent. Dogs and cats and raccoons are intelligent. Taking non-mammalian examples, consider parrots and ravens. Octopi and cuttlefish are pretty smart too. But if by intelligent we use the pragmatic SETI definition of being able to build a radio or other technology readily detectable over interstellar distances, intelligent life has only appeared once on Earth.
Given all of that, there are still obstacles to a civilization or culture spreading across interstellar space. There has already been a lot of speculation on this theme, both in the scientific literature and in science fiction, but I decided to design a hard sci-fi setting playing around with it anyway. I’ve used the results in a couple of variously-bad short stories and one never-completed NaNoWriMo novel (it reached 50,000 words, but would need an incredible amount of editing and a lot more material to flesh out the plot). A couple of years ago, I put the then-current version of the setting online here, but I’ve decided on some changes since then. Name-dropping, I call the setting “Fermi Problems”.
I’ll talk about the cultures in the setting more briefly here, one at a time. As last time, I ask you to take them to pieces – both the ways to get around the Fermi Paradox and the details of each group. I apologize in advance for a general lack of appropriate graphics, and beg for fan art.
People Who Can’t Get To Space
At the risk of making each culture in the setting a Planet Of Hats, I assigned a single primary reason why each of them had not spread across interstellar space in a detectable way before now (both actual ‘now’ and the several-hundred-year future ‘now’ of the setting).
For the first culture I designed, I decided that they had not spread into space because they couldn’t get off their planet. That meant a steep gravity well, which meant a gas giant planet. Fortunately, the idea of life on a gas giant isn’t entirely absurd. Carl Sagan and Ed Salpeter studied the possibility in some detail in 1978. Organic chemistry in the clouds, driven by lightning and UV and particle bombardment, becomes self-catalyzing. Microbial life can survive as long as it reproduces fast enough to outpace the droplets it is reproducing in falling down to points in the atmosphere where they get baked dead. Lift is better, so bags of heated gas and floating clots of aerogel come to dominate the biomass.
Sagan and Salpeter were considering the possibility of life in the atmosphere of Jupiter, which probably does not exist. So I put my fictional biosphere in the atmosphere of 47 Ursae Majoris b, one of the first extrasolar jovian planets to be found that wasn’t a hot Jupiter. For the purposes of the setting, 47 UMa b is ‘Ursa’ and 47 UMa the star is ‘Big Bear’.
Once there is a large population of floaters, life could evolve into niches that don’t have lifting power of their own. Some are parasitic plants. Others are animals, using heavier-than-air flight to get from one floater to another – powered by muscle power and biological chemical rockets (based on oxygen or methanol burned with hydrogen, as if a bombardier beetle secreted methane and burned it with oxygen) . One species of those animals eventually evolved intelligence and a technological society. Call them the ursians.
The ursians have had a technological society for hundreds of thousands of years. Artificial islands of aerogel blocks; blimps and jets to travel; genetic engineering of crops and of themselves; biochemical computers. But they have no silicon, no iron, no aluminum, no titanium, no uranium. The only source of those materials on the planet is grains of meteorite dust sieved out of the atmosphere. The ursians cannot build rockets capable of getting off of Ursa.
Orbital speed for the planet is ~75 km/s. No chemical fuel provides sufficient impulse. A gas-core fission rocket might be able to do the job, but requires uranium. A fusion rocket could do it, but that would mean setting off an H-bomb without a fissile trigger since steady-state fusion devices do not have sufficiently high power density to provide enough thrust. I had a large comet impacting the planet throw a floater into orbit, but the ursians on it did not survive. They are quite efficiently confined at the bottom of a very deep hole, and not able to build high-power radio transmitters either.
Does this work as a way to have extraterrestrial intelligence that has been around for a very long time and maintains high technology without being obvious across interstellar distances? Have I missed some way to throw objects into the sky or to generate monochromatic radio waves?