While browsing through today’s WIRED newsletter, I found a link titled “Life on earth given 500 million years“.

Apparently, two American scientists have written a new book. Accordinly, their publishing house has decided to give them some PR backing by putting out strange press statements. I haven’t read the book but I am pretty sure the content is accurately summarised by the following statement by one of its authors, Mr Brownlee, an astrophysicist –

“The disappearance of our planet is still 7.5 billion years away, but people really should consider the fate of our world and have a realistic understanding of where we are going (emphasis added).”

As much as I subscribe to mr Brownlee’s statement in principle, I suspect he does not really grasp the importance people are rightly attributing to the earth’s eventual fate, in some 7.5 billion years, according to current estimates – nil. We know that the universe will eventually collapse or freeze and still have not stopped procreating. We also know that growth is theoretically impossible for the universe as a whole, as there is only a certain unchanging amount of energy (and thus matter, remember e=mc²). But we still have not stopped thinking about supporting the economy by buying a new car.

The more distant the future, the less important it is to us. For a simple reason – there is an increased likelihood we won’t actually see it. As John Maynard Keynes famously put it, “in the long run, we’re all dead”. Finance people, the world’s finest when it comes to quantifying things, have put this into an equation and the result was the “Net Present Value”.

We might care about what happens to our grand children, and possibly even their grandchildren. But there comes a point where the Net Present Value, or the perceived importance, of future events becomes zero – as long as Keynes’ assumption about our personal fate in the long run is universally agreed upon.

Should that change, I would be the first to reconsider my judgment on books like the one mentioned above, even despite the logical impossibility of immortality (the longer you live, the higher the chances to die of an unnatural cause; if you could theoretically live forever, the possibility of an unnatural death would logically become infinite; and yes, this “unnatural” death could then be caused by the earth being fried or a freezing universe).

Until then, however, people really should NOT consider the fate of earth in 7.5 billion years. Sure, it’s an interesting fact to know, but, honestly, more than anything, it’s a number you don’t need. What people really SHOULD consider is the fate of earth in, say, 50 years.

That’s obviously a very partial analysis, but it would be a far more relevant albeit far more complicated one. Which is surely why too few actually do attempt such an analysis. But it would certainly yield some numbers one could actually need.