Happy Friday! 
Since it's end of the work week, I get to kick off my work shoes and write about what's been rumbling around in my mind since my last (first) post.
In particular, I was thinking about the explanation that 100 femtoseconds is the length of time is takes for light to travel the width of a human hair.
Dang, I *love* stuff like that, i.e., taking a complicated concept and bringing it down to earth.
I could've said "a hundred femtoseconds is a hundred-quadrillionths of a second." Or "ten to the minus thirteen seconds." Or "zero-point-zero-zero-zero-zero-zero-zero-zero-zero-zero-zero-zero-zero-zero-one second long." And you'd probably say something like, "Whoa, that's a lot of zeros."
But would you get it? 
Because all those zeros don't really explain how long 100 femtoseconds is, in everyday terms.
So what's this got to do with consumption, you ask?
Okay, get ready, here comes the whiplash.
From 2011 to 1880.
ZAP!
I have been reading a lot of stuff about consumption in 1880. (Not "consumption" as in consuming food or goods, but "consumption" as in tuberculosis.) It's hard to grasp in this day and age just how insidious and downright  frightening tuberculosis was back then (just like it's hard to grasp the concept of a femtosecond). 
I was getting some really good information, but wasn't getting the immensity of the problem.
Until....
 La miseria (1886) by Cristóbal Rojas (1857–1890)
... Tuberculosis was EVERYwhere in the 19th century ...
... I read the "The Salisbury Plans in Consumption" in the Transactions of the American Medical Association, 1880 (held in NYC). The author, Ephraim Cutter, M.D., opens his paper by describing the extent of consumption:
It  is estimated that one-quarter of the human deaths is caused directly or  indirectly by what is commonly called consumption. Taking man to  comprise 1,500,000,000 of individuals living on this globe, and the rate  of annual mortality to be one in fortyfive, there is a total of  33,333,333 yearly deaths. One-quarter of this number gives 8,333,333  annual victims offered on the altar of consumption. The intellect is  unable fully to comprehend this vast number. Allow us to try to measure  it by some common gauges. I find I can write my name readily ten times  in one minute. It would take me 833,333 minutes to write it as many  times as there are annual consumptive deaths. That is, it would take 1  year, 213 days, and 16 hours of uninterrupted writing simply to inscribe  the names of this host, if on an average they consisted of thirteen  letters.
Suppose the vast company could be marshalled in  rows four deep and two feet apart, this host would reach 770 miles in  length, and occupy 10 days and 17 hours in passing a given point at a  continuous rate of three miles an hour.
If the coffins of this  host averaged three feet in length, and could be placed end to end, they  would reach 24,999,999 feet, or about 4733 miles, or farther than from  here to Liverpool. Their funerals, at an average cost of ten dollars, would sum up $83,333,333.
Bringing the matter down to the United States, with  a population of 45,000,000, we have 250,000 annual deaths from  consumption. A mortality of 20,000 deaths in the late epidemic of yellow  fever convulsed the nation and cost $27,000,000. How can we estimate  our annual monetary loss from one-quarter of a million deaths from  consumption? If the deceased had been associated in an organization, it  would take its secretary to call off the roll, at the rate of 36 names a  minute, 4 days, 19 hours, and 44 minutes of continuous phonation.
Now I get it.