Fade in: 1963. Your grandmother, 24-years-old, is blowing smoke rings on an airplane. Wide pan: 85 strangers marinating in a churning cloud of hot, poison breath.

The question I struggle with when I think of once-ubiquitous airplane smoking is this: Why didn’t those people realize how disgusting they were?

Then come my happy childhood memories of smoky restaurants. The good old days when there was a chicken in every pot, an ashtray on every table. My grandma ran a little restaurant where I’d eat some Sunday mornings among the chain-smoking regulars.

It’s so strange to me that right now in Illinois, there’s a class of sixth-graders with no living memory of the smoking section at Chili’s. When some kid hears about life before the smoking ban, I imagine his first thought is something like: Why didn’t those people realize how disgusting they were?

The answer, in short, is that we’re all blind to the nastiness of our social norms; what looks hideous in retrospect was totally cool at the time.

It took decades of medical testimony and public-relation campaigns and a fair amount of death to push smoking quite literally to the periphery of public life. For years, we clung to cigarettes through warnings about cancer and the dangers of secondhand smoke, though appeals to vanity and a deluge of countervailing propaganda.

It’s only now, in the era of the indoor smoking ban, that we can look back and understand how smelly and polluted and cancerous our public spaces were.

My God, how oblivious we were.

Cut to New York City, Monday afternoon. A judge strikes down Mayor Bloomberg’s planned prohibition of sugary drinks in excess of 16 ounces on the eve of its implementation. Arbitrary and capricious, the judge says.

A reasonable appraisal, but here’s the real cause of death: Bloomberg’s big-soda ban was ahead of its time.

The many parallels between Bloomberg’s soda ban and any indoor smoking ban are not readily apparent. Cigarettes are manifestly offensive. They stink; there’s the coughing and the wheezing and the disease. They actively hurt innocent bystanders. Soda doesn’t offend, it causes no immediately apparent collateral damage.

But consider the long-term effects of both products. More cigarettes means more chronic disease and death, higher health-care costs, lower productivity, more debt, weaker economy. Similarly, more soda means more obesity, more chronic disease and death, and so on in the above manner.

This isn’t a theoretical connection; this is happening. A study of more than 33,000 Americans published last fall in the New England Journal of Medicine suggested that sugary drinks are a leading cause of widespread obesity. Annual health-care costs for obese people are, on average, $2,740 higher than health-care costs for people at a better weight.

Health-care spending, inflated by obesity and related disease, is the single largest driver of federal budget deficit growth; an obesity-related decline in productivity is an economic drag.

Through this macro lens, large-soda bans — like smoking bans — would make solid public policy. This is doubly true in Iowa, the No. 10 obese state in the United States and the fourth-most obese state outside the Old Confederacy, according to last week’s rankings from Gallup.

Sooner than later, we’ll have to take some unpleasant steps to fix the way we eat and drink.

Recognize that 70 percent of our food is processed. National soda consumption has fallen over the past decade, but per capita soda drinking is still far higher in the United States than anywhere else in the world. Eleven percent of our calories come from fast food every day; for people ages 20 to 38, that number is 15 percent.

We’re addicted to some seriously vile stuff, and not one of us is immune; if it came down to it, I’d probably sell my molars Fantine-style for chicken nuggets and a Coke.

Whether we recognize it or not, our next great public-health fight is against Big Junk-Food, and our best weapons are rules and regulations. Shout about freedom for as long as you like, but understand that the longer we cling like generations before us to an unsustainably gross lifestyle, the more permanent the damage becomes.

Fade into the era of the soda ban.

Close on your grandchild, 6-years-old, cross-legged on the floor some day in the distant future. You tell her a story about when you were a kid, slurping on a 44-ounce Circle K mug of a fluorescent, body-rotting sludge called Mountain Dew.

She’s disgusted.