No more. "Acid rain, nuclear power, infectious diseases -- the world is a little different," he said.

It was the nuclear power issue that first got him interested in public knowledge of science, when he was a graduate student in the 1960's. "The issue then was nuclear power," he said. "I used to play tennis with some engineers who were very pro-nuclear, and I was dating a person who was very anti-nuclear. I started doing some reading and discovered that if you don't know a little science it was hard to follow these debates. A lot of journalism would not make sense to you."

Devising good tests to measure scientific knowledge is not simple. Questions about values and attitudes can be asked again and again over the years because they will be understood the same way by everyone who hears them; for example, Dr. Miller's surveys regularly ask people whether they agree that science and technology make life change too fast (for years, about half of Americans have answered yes) or whether Americans depend too much on science and not enough on faith (ditto).

But assessing actual knowledge, over time, "is something of an art," he said. He varies his questions, as topics come and go in the news, but devises the surveys so overall results can be compared from survey to survey, just as SAT scores can be compared even though questions on the test change.

For example, he said, in the era of nuclear tests he asked people whether they knew about strontium 90, a component of fallout. Today, he asks about topics like the workings of DNA in the cell because "if you don't know what a cell is, you can't make sense of stem cell research."

Dr. Miller, who was raised in Portsmouth, Ohio, when it was a dying steel town, attributes much of the nation's collective scientific ignorance to poor education, particularly in high schools. Many colleges require every student to take some science, but most Americans do not graduate from college. And science education in high school can be spotty, he said.

"Our best university graduates are world-class by any definition," he said. "But the second half of our high school population -- it's an embarrassment. We have left behind a lot of people."