Human lives in extremely large numbers
The Census Bureau says there are approximately 7,768,000,000 people alive in the world today. That's a lot of people -- far more than the human brain can easily conceptualize. (Apparently, our brains make an inconvenient jump from simple primate math to object-based math, making us think of "billions" much the same way we might think of "bananas". Alas.)
■ If you were to take a single day on Earth and add up the 7.7 billion individual days experienced by every one of us, you'd accumulate quite the diary. There was a rather ambitious film project that tried to do something like that, capturing a glimpse of the same day in every country on the planet. But even that film was compressed into just 104 minutes.
■ But supposing instead that you could take those 7.7 billion days and play them out in sequence, one at a time, one after another non-stop, how long would it take? The math seems obvious: 7.7 billion person-days, divided by 365.25 days per year, yields 21,081,451 years' worth of human experience taking place for every 24 hours on this pale blue dot.
■ How long is 21 million years? The dinosaurs went extinct 65 million years ago, but they're pretty hard to conceptualize outside of myth anyway. Looking closer to our own family tree, the closest science has documented is an early primate that might have walked upright 7 million years ago.
■ So what this means is that every 24 hours on Earth, human beings experience a cumulative passage of time (laid end-to-end, as it were) that is three times longer than every day that has passed since the earliest possible hominids emerged. (Humans and chimpanzees shared a common ancestry until 13 million years ago.
■ The point to this conceptual math is deceptively simple: Anything we can do to improve material standards of living or the dignity of the common person on a mass scale, we should seek to do with a sense of urgency about the impact. A non-trivial number of the people who have ever lived are alive right now, so we shouldn't be shy about doing our best to make those lives better.
■ We should approach our decisions with appropriate modesty, of course -- we can be embarrassingly wrong if we're not careful. But there is much work to do in the world, and every little increment of progress -- if it reaches enough lives -- can have an impact that far outstrips (in human-days of life experience) the number of days humans have even walked the face of Earth. In the words of Jonathan Sacks, "The world will not get better of its own accord. Nor will we make it a more human place by leaving it to others -- politicians, columnists, protestors, campaigners -- making them our agents to bring redemption on our behalf." Every day is worth 21 million years.