## Sunday, July 24, 2011

### Elchanan Mossel on life, counting, and comparisons.

Elchanan Mossel has been visiting Microsoft Research for the past few days. In his work, he particularly likes reversible Markov chains. I missed an opportunity to ask him for his views on research, but, instead, the other day, as a spin-off of the topic "To hike, or not to hike", he offered me his opinion on life.

He is against counting people's age as the number of years elapsed since they were born. Instead, he wants to count in reverse, starting from the time when they will die and going back in time until the current date. Why? Because that's what really matters if you want to use that number as a gauge of how much deference to show someone. If the person is only a few hours or days from dying, of course you will most of the time yield to their wishes: it's their last chance to enjoy life, whereas you will get other opportunities later, after they are gone. Similarly if someone has only a year or two to live, whereas you have twenty or thirty years.

Of course the problem is that we do not know in advance exactly when someone will die. So, a natural solution is to use the person's current age as a proxy: the more years have elapsed since their birth, the closer they are to death, on average. Elchanan maintains that it's just a proxy, and that when other knowledge gives more information on the unknown date of future death, one should take it into account.

What's the upshot of this theory? The result is that, in spite of our age difference (I am his senior by 9 years), because of the difference in our respective physical health, he claims, or at least he implies, that I legitimately ought to show him respect and deference.

I think that that's right in line with yesterday's post on "Math madness".

#### 1 comment:

1. Maybe this is also why babies are more "respected" than 30-year olds, because (I think) there's more likelihood of a baby dying within the next year than a 30-year old.