Wednesday, January 14, 2015

Stephen Hawking's voice

Stephen Hawking in the 1980s
I learned something interesting today: I am among the last people who ever heard Stephen Hawking's real voice.

On Tuesday, April 23, 1985, Hawking gave a talk titled "Why Time Goes Forward" at Mandel Hall at the University of Chicago. I was a freshman that year, and I was in the audience.

In 1985 (30 years ago!), Hawking was pretty much the figure you see on the cover of "A Brief History of Time," published three years later: wheelchair-bound, bone-thin, as twisted as tree roots. He spoke in a hoarse, squeaky whisper. Essentially unintelligible, except to people in his inner circle, he was accompanied on stage by an English graduate student, bluff and robust, albeit with slightly thinning blond hair, who "translated" him phrase by phrase.

It was like listening to an oracle. Hawking would laboriously emit 30 seconds or so of rasps and squawks. These were in fact sentences, well-crafted and dense with thought, which the grad student would render in plummy Oxbridge tones. There were some jokes mixed in. To my great elation, as the talk progressed and my ear grew attuned, I was able to discern a couple of phrases amid the squawks, confirmed by the ensuing repetition.

What I did not know until now is that Hawking lost his voice just a couple of months later. Via Wired's great article on Hawking's IT and voice synthesizer setup (HT The Browser), I learned that he caught pneumonia in summer 1985 while visiting CERN in Geneva, and had to have an emergency tracheotomy. Since then, according to Wired, his voice has been that of "Perfect Paul," a voice developed for an early text-to-speech synthesizer by an MIT engineer, Dennis Klatt, who used his own voice as a model.

I remember Hawking's Mandel Hall talk fairly well, which is good, because the journal entry I wrote afterward gives maddeningly little detail, (though I did note for posterity that the grad student sported a yellow necktie). Hawking began by showing us a short film of plates falling off a table, then ran the same film in reverse. In real life, shards don't leap off the floor and reassemble themselves into chinaware, but why not? You can't find time-directionality in physics equations as such. They're all time-symmetric.

That led into a discussion of the various "arrows" of time. Hawking mentioned three: the entropic (the direction of increasing disorder), the psychological (which points in the same direction as the entropic, since brain processes are physical processes) and the cosmic (the direction taken by the universe).

When the universe is expanding, the cosmic and entropic arrows point in the same direction. When the universe is contracting, however, entropy is decreasing, so the entropic arrow flips. This raises the unsettling possibility that sentient beings in a contracting universe could believe themselves to be living their lives forward from birth to death, making choices and controlling their fate, when in fact the universe is rolling serenely in the other direction scrolling them backward from death to birth. If that were the case, those sentient beings -- us, for example -- would never know the difference.

Hawking closed by suggesting that the universe could be a "smooth" space-time object, without a tell-tale singularity (i.e., the Big Bang) that you could point to and say, "This is where it started." It wouldn't need a beginning, it would just be.

Heady stuff -- "mind-blowing," says my skimpy journal entry. A lot of it is in "A Brief History of Time." How much of it physicists currently consider tenable, I haven't a clue.

A few years later, I listened to an audiobook narrated by Hawking in his synth-voice, and I remember thinking what an extraordinary evening that night at Mandel Hall had been. I now know I was even luckier than I realized.

Saturday, January 3, 2015

How to lie about flu vaccines in one easy step

I wrote a news article on flu the other day, and a reader emailed me asking, "How many people who get the flu got a flu shot?" I did a couple basic calculations and discovered something interesting (well, interesting to me anyway): The more people get the flu shot, the more easily the resulting statistics can be used deceptively to imply the vaccine doesn't work!

Why? I believe it's known as "conditional probability." Anyway, here are the numbers I ran:

According to the Centers for Disease Control and Prevention, the flu shot cuts people's chances of getting the flu by about 60%. (It depends on your age and health status, the accuracy of the vaccine that year, and so on, but we're talking back-of-the-envelope numbers here.) WebMD says your odds of getting the flu are 5% to 20%. I used 10% as my baseline (i.e., pre-vaccine) risk. For population, I chose 500,000, roughly the number of people in my county.

CASE A: Suppose 50% of the population gets a flu vaccine. (The actual 2013-14 rate was 46.2%.) That means 250,000 people are unvaccinated, while 250,000 get the shot. Of the first half, 10%, or 25,000, will get the flu. Of the others, 25,000 would have gotten the flu, but they have protection that's 60% effective, so only 40%, or 10,000, actually come down with it.  That still gives us 10,000 people complaining that the vaccine didn't do them a lick of good, but our population of 25,000 people who didn't get vaccinated and subsequently got sick is 2 1/2 times larger. Clearly, vaccination is doing its job.

CASE B: Now suppose that 90% of the population, 450,000 people, get a flu vaccine, and only 50,000 don't. We're protecting a lot more people: The vaccine will really show its worth now, right? Let's see.

Among our 50,000 unvaccinated people, 5,000 (10%) will get sick. As for the vaccinated majority, 10% of 450,000 is 45,000, but they have 60% protection, so only 40% get sick. Unfortunately, 45,000 times 0.4 is 18,000. Horrors! Among or population of sick people, the number who got vaccinated vastly exceeds those who didn't. To be precise, the vaccinated group accounts for 78% of the total. Clearly, vaccines are dangerous and make you more likely to get flu!*

CASE C: If the CDC could achieve 99 percent vaccination compliance, then in my hypothetical population of 500,000, there would be 20,300** flu cases, and 19,800 of them - over 97%!! - would be people who got the shot.

When you work it out step by step, it's easy to see what's happening here - a smaller portion of a large number can be (much) bigger than a larger portion of a small number. But if you're innumerate, a writer of clickbait headlines, an anti-vaxxer, or some combination of the three, you write PATIENTS SICK WITH FLU 97% MORE LIKELY TO BE VACCINATED THAN NOT and all hell breaks loose.

The moral: The worse the stats look, the better off we are! 

The follow-up moral: Get a flu shot.

*In case it isn't sufficiently obvious, this "inference" is 100% wrong.

**Note that our total case numbers drop as vaccination spreads: 35,000 to 23,000 to 20,300. Even at 60% effectiveness, vaccination works.