Name: What Happens When Science Clashes with the Public?: Crash Course Scientific Thinking #7
Uploaded: 2026-03-18T21:32:03.000Z
Duration: 12 min 26 s
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I know that, you know that, and the tobacco industry definitely knows that.

But not all that long ago, you couldn't even watch Saturday morning cartoons without being bombarded with messages that cigarettes aren't that bad for you.

Tobacco companies ran ads in magazines and periodicals saying that numerous scientists question smoking's risks, that there are many possible causes of lung cancer, and

that there's no proof cigarette smoking is one of them.

So if you had been there, how would you have figured out what was true?

Hi, I'm Hank Green, and this is Crash Course Scientific Thinking.

Before scientific knowledge reaches people like you and me, it takes a long, arduous journey, and

big stretches of it are dedicated to collecting, testing, and

scrutinizing empirical evidence, information collected through rigorous scientific methods that either support or refute an idea.

The the vast majority of scientific progress hums along quietly, its evidence becoming widely accepted without much hullabaloo.

You won't hear pundits debate whether carbon has six protons, and

there won't be dramatic headlines about the mating behavior of sea slugs, though I for one definitely would and do read those articles.

But here's the Sometimes science produces a nugget of knowledge that resists the status quo.

It challenges an economic system or a hierarchy or a choice people make in their lives.

And when it lands with the public, tensions can flare, which is what happened in 1964 with smoking.

So in this episode, we're going to do two things.

First, we'll peel back the curtain on how the scientific process pieced together evidence about the risks of smoking.

And then we'll unpack why that knowledge got so much pushback and what we can learn from the tale about the public consumption of science news.

At the Beginning of the 20th century, lung cancer was so rare, doctors treated cases of it like once in a lifetime learning opportunities.

But then, in the 1920s and 30s, lung cancer rates started to spike, and

scientists began working to figure out why.

There were a lot of early ideas about the possible cause.

Maybe it was atmospheric pollution or newly paved roads.

Maybe it was X rays, poison gas from World War I, or the after effects of the 1918 flu pandemic.

But as we learned in an earlier episode, correlation doesn't mean causation.

So over two decades, scientists tested different explanations and shared the results with each other.

Each study was like a pebble added to a pile of evidence.

Scientists had to weigh that evidence by examining each study skeptically and asking things like how well was the study designed?

Did it find a strong or weak relationship to lung cancer.

And how directly did the methods actually get at the question they were trying to answer?

For some explanations, no evidence emerged.

But eventually, four main lines of evidence pointed to one suspect.

Observational studies which had followed groups of people over a period of time showed that smokers developed lung cancer at higher rates than non smokers.

But there were other factors in people's lives that could be affecting cancer rates.

Experimental studies were done on mice because you can better control conditions in a lab, and

mice exposed to tobacco developed tumors.

What actually happens when lungs are exposed to smoke?

Further studies showed that cigarette smoke destroys cilia, the tiny structures in lungs that keep out bad stuff.

Tobacco smoke itself contains a chemical compound that was previously shown to cause cancer in people exposed to coal tar.

All that evidence, when weighed collectively, began to tip the scales.

By the late 1950s, scientists had reached a consensus, widespread agreement, given all of the evidence, that smoking was the leading cause of lung cancer.

So in 1964, the US Surgeon General, himself a smoker, announced to reporters that cigarettes cause lung cancer.

But for the public, that message got drowned out by a lot of noise.

this time, let's look at what was going on in the public view.

Even in the 1930s, people suspected smoking wasn't exactly great for you.

But tobacco companies worked to stay ahead of the narrative, boasting that their cigarettes were healthier, safer, gentler, fresh as mountain air.

reynolds Tobacco Company ran ads citing studies that claimed more doctors smoke Camels than any other cigarette.

And you want to know how they got that statistic?

By giving doctors free Camel cigarettes and then asking them what kind of cigarettes they smoked.

By the 1950s, tobacco companies knew about the mounting scientific evidence, but

they were still invested in selling their product.

Instead of our cigarettes are better for you, the ads became, we don't know yet if cigarettes are bad for you.

And by doing so, they manufactured a controversy that didn't actually exist.

In 1954, a committee called the Tobacco industry Research Committee, which was formed by the tobacco companies, released a statement claiming the link between smoking and lung cancer wasn't settled and they would be researching the issue themselves.

These people would have thrived on social media.

This went on for decades, Long after the scientific consensus had been settled.

The tobacco industry, distracted from smoking's harms by funding and publicizing research looking into alternative explanations for lung cancer.

They suppressed and criticized studies that found smoking was bad for you.

And all the while, they publicly denied that smoking was risky or addictive and blasted ads that made cigarettes seem as enticing as possible.

They did all of this knowingly and strategically to keep making money.

A 1969 internal memo at the tobacco company Brown and williamson stated, doubt is our product.

Since it is the best means of competing with the body of fact that exists in the mind of the general public, it is also the means of establishing a controversy.

The tobacco industry preyed upon people's cognitive biases, those predictable patterns our brains tend to take that can sway us away from accepting valid information, Especially when it challenges something we already do or think.

The news that smoking causes cancer just didn't vibe with a world where smoking was common, widely accepted, and

When you're addicted to something, you pay more attention to reasons to keep doing that thing.

And the tobacco industry was willing to give smokers those reasons, even though the reasons were made up.

They systematically attacked the widely accepted scientific explanation in order to sow doubt among the public.

But here's what finally turned the tide against in the 1990s, scientists uncovered evidence of exactly how cigarette smoke can trigger a normal cell to become a cancerous cell.

Then, in 1998, a major settlement required the tobacco industry to pay up billions of dollars for the damage they had caused.

the tobacco industry still tried to spin the narrative, the message this time.

They claimed they'd always been transparent about the risks of smoking and said that it had always been an individual's choice to take those risks.

Which brings me to another common point of tension that can make scientific knowledge seem controversial.

Sometimes scientific knowledge clashes with people's values.

There's stuff science can tell us, like the precise mechanism that causes a cell to become cancerous, or how much smoking increases your individual risk of developing cancer.

But science can't tell us what to do with that knowledge.

It's on us as individuals and as societies to decide what to do now that we know what we know.

For example, in the early 2000s, as the dangers of secondhand smoke became more widely known, Many cities and states began banning smoking.