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Your body wasn’t built to last: a lesson from human mortality rates

How’s this for a morning jolt, stronger than your coffee? Stumbling across a blog post that begins with:

What do you think are the odds that you will die during the next year? Try to put a number to it — 1 in 100? 1 in 10,000? Whatever it is, it will be twice as large 8 years from now.

This is from a really interesting blog entitled Gravity and Levity, and written by Brian Skinner, a postdoc in theoretical condensed matter physics. And with a bit of irony I note that the date of the original post is 2009, which is pretty close to the 8 years he talks about in the above quote.

It’s pretty intense reading and so I’ll give you some highlights and then direct you to the original post.

So about this doubling within 8 years thing…. Here are some factoids.

  • first noticed by the British actuary Benjamin Gompertz in 1825
  • now called the “Gompertz Law of human mortality”
  • holds true across most countries, although the number 8 may be 7, or 9. The point is, your odds of mortality will double in X years.

Here’s how the author explains it using his own life as an example (because my life is no example, that’s for sure):

Your probability of dying during a given year doubles every 8 years. For me, a 25-year-old American, the probability of dying during the next year is a fairly minuscule 0.03% — about 1 in 3,000. When I’m 33 it will be about 1 in 1,500, when I’m 42 it will be about 1 in 750, and so on. By the time I reach age 100 (and I do plan on it) the probability of living to 101 will only be about 50%. This is seriously fast growth — my mortality rate is increasing exponentially with age.

He cites census data that still shows the veracity of Gompertz Law and this is the equation:

P(t) \approx e^{-0.003 e^{(t-25)/10}}

Skinner muses that bodies have a built-in expiration date and discusses some other theories of mortality such as The Lightning Bolt Theory, The Accumulated Lightning Bolt Theory – both of which he says are just not accurate because if they were, we’d have people dying at age 300 and our bodies just are not built for that.

This is a fascinating blog piece and if you’re in to such questions, well worth the read. Food for thought and not necessarily cheery news to start this holiday week.

Full story here: Gravity and Levity.

More stories about Physics.

Photo credit: Canva.com

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