The Doomsday Argument

Series on the Anthropic Principle:
The Anthropic Principle
The Doomsday Argument

65 million years ago, dinosaurs roamed the earth. Then, all of a sudden, they were gone. Something happened, we think it was a meteor strike, that made the earth uninhabitable for them. 251 million years ago, a major volcanic eruption and the ensuing global climate change killed most of the life on the planet. In total, there were 5 major extinctions in Earth’s history.

Human stories are full of tales of the end of the world. In Norse mythology, there is Ragnarok. In the Bible, Armageddon. In modern times, we have the Terminator, Galactus, disaster movies. We have fears of climate change, asteroid strikes, nuclear war, and uncontrollable artificial intelligence. It’s clear we have a question deep within our psychology: is humanity about to end?

The astrophysicist Brandon Carter thought so 35 years ago. The argument went like this: assume human population continues to grow exponentially until some cataclysmic event reduces our numbers to near or total extinction. If the population doubles every 50 years, then by the Anthropic Principle, you had a 50% chance of living in the final 50 years of human civilization, and a 50% chance of dying sometime in the entirety of human history before then.

If this were the entire human population over all time, probability says we would expect to find ourselves in the spike on the right side.

This seems crazy, but it isn’t immediately obvious why. When I argued against it way back in the day, I was completely wrong. The first thing I said was that because you and I are you and I, we are not randomly selected from human history. This is nonsense. If we choose randomly from all humans who ever have or ever will live, you and I are among the possible choices. It’s a perfectly valid framework for asking questions, and that’s what the Anthropic Principle does.

The other bad argument I had against it was this: “Pick a point in history between the dawn of agriculture and the end of time, and the Doomsday Argument will give the same result: humanity is about to end.” This is true, but it is not a counter to the Doomsday Argument. The fallacy was that I switched from a random sampling of humans to a random sampling of time. And because population increases over time, a random sampling over time gives the earlier times undue weight.

So then what is the counter-argument? There are a few. The first one that jumps out to me is the fact that it is really hard to think of a scenario that will make humanity go totally extinct. Think of your favorite existential disaster: catastrophic global warming, nuclear annihilation, super-virus, supervolcano, autonomous weapons that decide they want to destroy all humans. If any of these were to wipe out the vast majority of the human species, it would be a terrible, tragic event unparalleled by anything in human history. However, we only need a small number to survive, and they will be able to repopulate the planet and restore civilization.

A big enough asteroid strike could make the Earth uninhabitable, but we have the technology to see asteroids that big years before they would hit us, sometimes decades, plenty of time to nudge them off-course. There are no supernova or gamma ray burst progenitors close enough to harm us with their explosions, nor alien civilizations close enough to invade. And the sun won’t get hot enough to turn Earth into another Venus for another few hundred million years.

What could cause humanity to go extinct? There is only one realistic example that I can think of: superintelligent AI that wants to exterminate humanity. How likely is this? Well, that deserves a discussion of its own. We can rest assured that there are many extremely intelligent people thinking about this topic, and working hard to foresee the possible risks and dangers of developing artificial intelligence. Of course, there is always a possibility that we will miss something, but the more we think about it and work on it, the more likely we are to spot the dangerous paths and go around them.

The other thing that could cause humanity to go extinct lies in the unknown unknowns. It may be that some technology will be invented that is extremely easy to make, and can wipe out humanity. This is sometimes called a “black ball technology.” If such a potential technology exists, then anyone with the right equipment, materials, and recipe would be able to destroy humanity, and given that there are billions of people on the Earth, we would be in serious trouble.

However, the very thing that makes us vulnerable to black ball technology also guards us against it: technological progress and expansion. Once we are able to leave our home planet and start new civilizations on other planets and moons and giant artificial space habitats, then we will be able to survive even something that destroys all life on Earth.

A second problem with the Doomsday Argument is that it assumes humanity will continue to grow exponentially, and then be cut down to a level so low it cannot recover. We already know this model is incorrect, because the rate of human population growth is slowing. If we apply the anthropic principle to another function, say, a linear increase, we find that we have a slightly more than 50% chance of living within the final third of human history. That final third could have a range of anywhere between 100,000 years and 150,000 years. And 50% means there is an equal probability of living outside of that time. So with linear growth, the Doomsday Argument doesn’t tell us much of anything at all!

Since the area under the curve is about equal in each section, we would be about equally likely to find ourselves in either of them.

The final problem with the Doomsday Argument is that it assumes the growth of civilization will stop with some catastrophic event. There are plenty of other models of human population that work perfectly fine with the anthropic principle. For instance, if it looks more like a bell curve, we would be more likely to find ourselves near the top. If it levels off, we would be equally likely to find ourselves anywhere along the level period. If it looks bumpy and wavy, we are more likely to find ourselves near one of the peaks. It’s very difficult to say what the human population curve will look like in the future, because every model carries with it plenty of assumptions.

There is one sense in which the Doomsday Argument seems to get things right. When we look out into the universe, we see a vision of a possible future where life, humanity’s descendants, and perhaps alien species, thrive and live around every star and in the spaces between. The number of people in such a multitude of societies astronomically outnumbers the number of humans who have ever lived. Therefore, regardless of what the population curve looks like, the odds of living on such a civilization’s planet of origin before it spreads out into the galaxy is astronomically small. It’s like winning the lottery, and the reward being another lottery ticket, which wins again, and is rewarded with a third lottery ticket, which wins yet again.

Yet here we are. And we have two options. One, we can look at the staggeringly improbable odds that we would find ourselves at this time in such a universe, and hang our heads in despair, declaring that these odds mean such a civilization is doomed never to happen. The other option is to accept that the future has not happened yet; it depends on what we do now. So since we have already won the cosmic lottery, let’s do our part to build the machine that generates our winning tickets. The world hasn’t ended yet, so as Samuel L. Jackson says, let us act as though it intends to spin on.

Why are Some Things Impossible?

Impossible. We’ve all heard this word. Sometimes it is used as an excuse to give up. Sometimes as a reason to pursue other things with our time. Sometimes in the context of science and technology. When we want to encourage imagination, we tell our kids (and sometimes adults) that nothing is impossible.

If something is impossible, it can’t be done. Seems straightforward enough. But what makes the difference between whether something is possible or impossible? In asking this question, we find there is not one single answer, but several tiers, each nested within the one before.

Logically impossible

At the most bedrock level, we have logical impossibilities. These are things that cannot exist or cannot be done because they contradict themselves. These include mathematical contradictions, as well as things that contradict their own definitions.

For example, suppose among the men in a certain town, there is a barber who shaves those, and only those, who do not shave themselves. Does the barber shave himself? If so, he is not the barber. Does he not shave himself? If so, then he shaves himself. Therefore, a barber who fits this description cannot exist.

Other things that are logically impossible: A square circle in cartesian coordinates. A solution to a 2x2 sudoku puzzle with a 1 in the top left and a 2 in the bottom right. A legal crime. A dry ocean.

Physically impossible

We don’t live in a universe where everything logically consistent is possible. Everything that exists has a nature, described by laws of physics, and these natures render a whole host of things impossible.

I should pause to mention the distinction between the true nature of reality and our current theoretical understanding of it. Science is very much a work in progress, so there are many things we don’t know yet, and many we think we know but are wrong about. Nevertheless, there are things that are logically possible, but impossible within the true laws of physics, whatever they turn out to be at perfect resolution.

With that in mind, we can talk about what would be impossible if our current understanding were correct, and let it be a proof of concept. Some things that are impossible in our universe, but logically acceptable, are perpetual motion, going faster than light or backward in time, getting out of a black hole, and reducing the total entropy of a closed system.

Technologically impossible

Even within the laws of physics, many things are not possible to us yet, because we do not have the technology to do them. This tier is vast and rich, and in considering what is inside it, we can imagine mind-bogglingly bizarre futures.

In the near term, we have things like mind-computer interfaces, autonomous cars, and quantum computers. A little further out, we might expect to invent nuclear fusion power plants, space elevators, superconducting power lines, weather control, conscious artificial intelligence, biological immortality, revival of extinct species, human colonies all over the solar system, and so much more.

These may seem like science fiction magic to untrained ears, but the difference between them and magic is that people can envision a path toward inventing them that makes sense in the context of modern science.

Economically impossible

Even when we know how to do things, we still need the will and the resources for them. As humanity finds new ways to harness energy and resources, especially in space, more and more things become possible. These include things like space ships with spin gravity, particle accelerators that dwarf CERN, interferometer telescopes the size of the solar system, and buildings tens of thousands of meters high.

But when we’re talking about the merely economically impossible, we don’t have to limit ourselves to such small scales. We could build an orbital ring around the Earth’s equator, orbiting just outside the atmosphere, with launch platforms for shuttles and rockets. We could mine asteroids and use their materials to build giant ships in space. We could envelop the sun entirely in solar energy collectors, a Dyson sphere. We could build giant reflectors to direct all of the sun’s light in one direction, effectively a rocket thruster that could move the solar system. All under known science, and with technology that has already been invented.

Cognitively impossible

Here we come to the last, most easily surpassed level of impossibility. These are things which are impossible only because people believe they are. As soon as people put their minds and efforts toward it, it becomes possible. Many of the great inventions of history came about because someone or some group of people decided they were going to do what everyone else assumed to be impossible, from the Wright brothers inventing the airplane, to the USSR sending a man to space, to the US putting boot prints on the moon.

Today, the biggest example of someone challenging the cognitively impossible is Elon Musk. From SpaceX building bigger and better rockets, to the Boring Company digging tunnels under Los Angeles to solve traffic congestion, to Neuralink connecting people’s brains with computers. He, those who work for him, and many other entrepreneurs, bring the cognitively impossible into existence.

Other things that seem cognitively impossible: World peace. Meeting the basic needs of everyone on Earth. Tolerance and good will across political and religious divides. Governments that work for everyone. A business culture that cares about the poor, the workers, and the environment. Cultures where there are no social minorities or majorities. Cities floating on the ocean. Powering civilization and the global economy with sustainable resources.

All of these things are possible and doable given the technology and economic infrastructure we have now. Why don’t we? Well, there are a million reasons, all of which are unique to their particular challenge. But many of them can be overcome if enough people or the right few see through the curtain of the way things are, and aim their sights on achieving what many brush off as impossible. Not everything is possible. But the number of things that are is vast.

NaNoWriMo 2019

It’s November again! That means I, along with hundreds of thousands of other writers, will be jamming out a 50,000-word novel in 30 days.

I’ve done NaNoWriMo three times before, and each time, I upped the ante. In 2016, my goal was just to finish a story, which ended up less than 30,000 words. In 2017, I made myself write no less than 1,000 words every day. In 2018, I aimed for and reached 50,000 with a junk novel, using the sense of fun to motivate myself to meet the daily goal. And now in 2019, I’m going all in. This year, not only am I aiming for 50,000 words by the end of the month, I am writing the first draft of a story that I want to continue to work on afterward, and aim to get published.

That’s right, I’m about to start my first book that I’m aiming to publish. Goodbye fanfictions and practice stories, the real game is beginning!

This book’s working title is Earthbound: A Galactic Odyssey. It’s a hard science fiction story taking place a million years in the future. Inspired by Isaac Arthur’s video, “Hitchhiking the Galaxy,” humanity’s first gardener ship has seeded colonies to the edge of the Milky Way, and is ready to head off for the Large Magellanic Cloud. One of its citizens, an augmented, immortal human, decides he would really like to see Earth again. The story follows him as he travels back across the galaxy at slower-than-light speeds, revisiting some of the civilizations that have grown out of the colonies he helped plant. There will be space ships, AI, technology, speculative societies, and all kinds of futuristic stuff, almost all grounded in known science and realistic speculation.

Since it is intended to be a full-on adult sci-fi novel, chances are high it will end up much longer than 50,000 words, and take longer than one month to finish a full draft.

The writer’s group I was in last year didn’t work out, but I found a new one, which looks promising. Hopefully, this group can stick together, and we can give each other the feedback and energy we need in order to succeed as authors. If any of you from NaNo and Beyond are reading this, hi! Here’s to realizing our dreams!