Quantifying the Rate of Change

We live in an era that involves an extraordinary amount of change. To see this, consider the rate of global economic growth, which in recent decades averaged around 3 percent per year.51 This is historically unprecedented. For the first 290,000 years of humanity’s existence, global growth was close to 0 percent per year; in the agricultural era that increased to around 0.1 percent, and it accelerated from there after the Industrial Revolution. It’s only in the last hundred years that the world economy has grown at a rate above 2 percent per year. Putting this another way: from 10,000 BC onwards, it took many hundreds of years for the world economy to double in size. The most recent doubling took just nineteen years.52 And it’s not just that rates of economic growth are historically unusual; the same is true for rates of energy use, carbon dioxide emissions, land use change, scientific advancement, and arguably moral change, too.

So we know that the present era is extremely unusual compared to the past. But it’s also unusual compared to the future. This rapid rate of change cannot continue forever, even if we entirely decouple growth from carbon emissions and even if in the future we spread to the stars. To see this, suppose that future growth slows a little to just 2 percent per year.54 At such a rate, in ten thousand years the world economy would be 1086 times larger than it is today—that is, we would produce one hundred trillion trillion trillion trillion trillion trillion trillion times as much output as we do now. But there are less than 1067 atoms within ten thousand light years of Earth.55 So if current growth rates continued for just ten millennia more, there would have to be ten million trillion times as much output as our current world produces for every atom that we could, in principle, access. Though of course we can’t be certain, this just doesn’t seem possible.