If someone built a monument to U.S. metric conversion, it could take the shape of a 2-liter bottle of pop.

Funny, huh? Thirty years after the country went metric, and this is all we have?

It has been that long since Congress passed and President Gerald Ford signed the Metric Conversion Act of 1975, back when being all-international seemed like a good idea.

To many others, though, it has always seemed, well, foreign. It certainly does to fourth-graders today, confronting their metrics chapter in math class with no more awareness of what a kilogram feels like than their parents had. Same with kilometers and degrees Celsius.

"Dad, is a kilometer about like a mile?"

"No, I think it might be more like half a mile, unless it's a mile-and-a-half."

In 1971, a federal report warned that our country soon would become an island in a sea of metric. Apparently, we love island life. To the anti-metric, the system is hyper-rational, almost too precise. There's something human about the inch and foot, quart and gallon that's lost with metrics, critics say. To this way of thinking, weights and measures are as much cultural as practical.

Lorelle Young, president of the U.S. Metric Association, which has advocated metric conversion since 1916, said she understands the comfort of the inch-pound system, the emotional attachment. But clinging to it for these reasons isn't enough, she said. In a competitive, technical and global environment, metrics are the only way to go.

"We don't teach our kids to use manual typewriters," she said. "We don't wait for the ice man."

The metric system is based on 10s and uses descriptive prefixes, which makes it easy to learn. There are 100 centimeters in a meter, for instance. The confusion comes when people delve into complicated conversion equations to relate metric to inches and pounds.

Gabriel Mouton, a French mathematician and priest, gets credit for coming up with the system in the 1600s. The French adopted it in the late 1700s. The meter was figured to be one-10-millionth the distance from the equator to the North Pole. The length of the meter has been refined a couple of times since.

The inch-pound system came to us by way of the British, who are now more metric than we, even though many a British citizen still revels in resistance.

In truth, metrics has seeped into the U.S. vernacular beyond the plastic soda bottle. It's perfectly acceptable to speak of the 100-meter race in the Olympics or the local 5K run for cancer research. People happily buy 35-mm film and talk about the 3.6-liter engines in their cars. And, of course, the metric system is the language of science and medicine.

Even more significantly, Young said, metrics continue to overtake inches and pounds in industry and commerce. The car industry works in metrics. Skis are sized in centimeters.

"I call it stealth metrics," she said. "People accept it."

James R. Frysinger, a physics lecturer at the College of Charleston in South Carolina, has another term: "metric moments." They happen every day without upsetting anyone. Fat and fiber come in grams, sodium in milligrams. Computer speeds are in megahertz. Wine and spirits come in metric sizes only. Watts, volts and amperes are metric units.

While metric creep might indeed eventually transform us, in-your-face changes likely still will illicit derisive or angry reactions.

Try erecting highway distance signs in kilometers, for instance. Many of the 1970s signs that offered both miles and kilometers are long gone. A real estate agent who speaks in anything but square-footage would be as lonely as the Maytag repairman. Canadian weather forecasters using Celsius can tell you about the balmy 25-degree day ahead, but their U.S. counterparts certainly wouldn't try it.

Mike Thompson, a meteorologist at WDAF-TV in Kansas City, must be fluent in Celsius (everyday metrics) and Kelvin (scientific metrics) to deal with incoming temperature data. Celsius is used just about everywhere except the United States, but Thompson knows Celsius temperatures don't mean a thing to his viewers.

And, frankly, he likes Fahrenheit better for describing surface temperatures. Fahrenheit marks 180 degrees between the freezing and boiling points of water. Celsius has 100. In effect, the units of the Fahrenheit scale are closer together than in Celsius.

"I think it's more descriptive," Thompson said.

Meanwhile, the Food and Drug Administration is expected to consider a product labeling change that would allow -- not require -- manufacturers to list only metric sizes on products rather than listing both metric and inches-pounds.

Expect howling.

Even though the proposal makes sense in a global marketplace, Young said, she knows what some people will be thinking.

"This is America, and we're the best and first, and everyone should do what we do," she said. But that's not going to happen in weights and measures.

"It's more important to look forward, particularly when we're talking about our children," Young said.