What are the prospects of companionship in the universe? If microbes are found on a planet around another star, it'll be front-page news for sure, the scientists will be incredibly excited. It will change the field of astrobiology and astronomy forever. But the public may well psi and move on after a week or so. On the other hand, if intelligent life is found elsewhere, that's a game changer. In a sense, it will change everything our view of ourselves. Perhaps, the world's major religions will have to respond, we simply don't know how we'll react to this information. We can speculate on what the young Copernicus and Tycho Brahe might have said considering this possibility. The world, dude, this is awesome. Definite awesome. I mean like all those stars. Dude. There's millions of them. Like each one of those stars, it's like a Sun. Like wow, dude. That means like, there's tons of other solar systems. Yeah. That means that we're like. Like little specks. Like almost nothing. If we use the Earth as our example because it's the only place we can use with biology on it, we can consider three thresholds of evolution of biology and how they might manifest in the universe. The first threshold was the one that live pass through after a billion or so years when life became multicellular. On a microbial planet with just single-cell bacteria, there's a limit to the complexity or sophistication of biology. As soon as multi-celled organisms evolved on the Earth, that was a precursor to the rapid growth of larger creatures and eventually central nervous systems and brains. That's the first threshold. The second threshold is the development of central nervous systems and brains which took place in its first rudimentary forms about 800 million or 900 million years ago in the Earth's oceans. But really only flowered about 500 million years ago. These processing units for external information become a vehicle in natural selection for the development of yet better capabilities. Remember, that our brains are energetically unfavorable for an organism. It takes a substantial fraction of the energy we consume to operate our brains. Also our sensory equipment is quite sophisticated. Our eyes alone occupy about 10 percent of our energy input to make them function, they're so essential to our survival and functioning as high organisms. We will be general in deciding what a brain is and just imagine that it's a higher processing unit taking in complex sensory data. The third threshold which does not follow naturally are inevitably from the first is technology. We see on the Earth that there are creatures like marine mammals that quite possibly have interior lives, meta-cognition, perhaps even qualia, or feelings, or senses, awarenesses of their own mortality, we simply don't know. But they're sophisticated intelligent creatures that have never and will never develop technology unless they move on to the land. So it's certainly possible to have intelligence without technology making this a distinct and separate step in the chain of evolution. Remember that it took us awhile to develop technology. We have been anatomically modern with essentially no changes to our genetic makeup for about 40,000 years. But only in the last couple of 100 have we had technology, and only in the last 50 or so have we been able to venture off our own planet. It's a very recent and primitive occurrence because we haven't taken it that far yet. Still in the realm of speculation, we can imagine what might have happened on the many Earth-like planets that Kepler and other missions are going to find in the next decade or so. We also know the rough numbers and distances of these earth-like planets. Typically, they're going to be a dozen or so earth-like planets within about 30 light years, and a very large number in the Milky Way. The real estate is not just space but time, because earth-like planets formed probably within a billion years of the Big Bang there was sufficient carbon to make them. If we imagine the Earth-like planets arrayed in space through the Milky Way and pile them up vertically and make a picture of it, this picture would fill a piece of paper to show the nearest planets within 30 light years. But the piece of paper would extend into the sky about 10 miles high to stack up all the Earths in the Milky Way. That's the number of potential biological experiments there are. What do we imagine has happened on these biological experiments? There are various possibilities. In some, life may have been stillborn. Of course a large number of life may never have started in the first place. There others where the star would have lived a short enough time that life never had the chance to advance to multicellularity or the ability to have thoughts and intelligence. This is an unfortunate outcome. In our solar system, it would have happened if the sun was about twice the mass it is now. Its life would have been so short that life would have been extinguished before creatures moved onto the Earth's land. Other possibilities are that live stops reaches a stasis at some level of evolution and never progresses beyond that. Then in some particular cases, the transition both to intelligence and technology might have occurred, and it might have occurred quicker than it took place on Earth. This of course could have happened billions of years before the Earth even formed. For any advanced civilization, traveling through the galaxy at say one percent light-speed, which is not beyond the projection of our own technology, means you can spend the Milky Way in 10 or 15 million years. Small fraction of the age of the Earth, small fraction of the age of the galaxy. Therefore travel, transport or communication is essentially instantaneous. This is an argument that scientists have been aware of for half a century, that should intelligent civilizations exist in the galaxy, there's been plenty of time for them to check it out and explore. It's so hard to visualize the number of Petri dishes in the universe or even in our own galaxy that we can use the analogy of grains of sand. The number of Earth-like or nearly earth-like planets that have been discovered so far is the number of sand grains that was stick to your forefinger if you wet the tip. Most of these we know almost nothing about them except their mass and size. We know nothing about their detailed characteristics or true habitability, and these planets are all in our backyard within distances of a 100 or so light years. The number of habitable worlds by the estimate of exoplanets and astrobiologists in the Milky Way galaxy is about a billion. By our analogy with sand grains, that's the number of sand grains in a child's sandpit. Imagine the time it would take to inspect them all. But that's not all because the universe we know has a billion galaxies, and a billion galaxies would represent all the grains of sand on all the beaches of the Earth. If each of these are habitable worlds each of these is a potential biological experiment. Most people will not be excited by the discovery of microbial life on another planet, but they will be excited by the discovery of intelligence. If we look at the possibilities of space and time, we can consider three thresholds in the evolution of biological life on any world. The first, the move to multicellularity, which took over a billion years on the earth. The second, the development of intelligence, which took over three billion years on the earth. The last, the development of technology, which in human hands is the blink of an eye in geological time, and so it took four billion years of life on Earth before we could leave the planet. How many biological experiments are there? In the universe, as many as the grains of sand on all the beaches of the world. Just in our galaxy alone, probably a billion habitable spots including exomoons, as well as exoplanets. Each of these, a potential biological experiment, the outcomes of these experiments unknown.
