Children participating in Mathews Memorial Library’s summer youth program “Science Matters” had a special treat on Tuesday—a visit by Dr. Paul Vanden Bout of Mathews, retired director of the National Radio Astronomy Observatory on the campus of the University of Virginia in Charlottesville.

Vanden Bout discussed everything from the history of astronomical discoveries to black holes, then gave the large group of mostly rapt youngsters a chance to ask questions about whatever galactic matters they chose. He explained the reasons that ancient thinkers made assumptions about the physical world that later proved to be wrong.

“They weren’t stupid,” said Vanden Bout. “They were really smart. They explained things by what they saw.”

Because the Earth was big and solid, he said, the initial assumption was that it was the center of the universe. But as discoveries were made, knowledge was gained, and science progressed.

First, while it’s easy today to see that the Earth is round because astronauts have taken actual photos of it from space, early scientists had to figure it out by putting together bits of information garnered from observation. They watched ships sail away and disappear from bottom to top, noticed that the night sky was different if they went north rather than south, and observed a lunar eclipse, with the shadow of the Earth moving across the moon.

Early Greeks didn’t know the Earth moved, said Vanden Bout, and there were good arguments for why it didn’t. For instance, if the Earth were rotating, why couldn’t the effect be felt, and why wouldn’t it create a big wind? If the moon were rotating around the Earth, why didn’t it move away and get lost? But through careful observation and thought, over time, scientific minds eventually figured out the answers. Isaac Newton developed the theory of gravity, which explains why objects remain on the Earth, why the moon continues to rotate around the planet, and why the planets rotate around the sun.

Then someone figured out how to shape glass and make a lens for eyeglasses, said Vanden Bout, and that led to development of first the microscope, then the telescope, and finally scientists could actually see the planets.

“It was observed and proved,” he said.

Vanden Bout had the children use their mathematical skills to work out how fast the Earth rotates—1,000 miles an hour—and he shared a few more staggering numbers. The earth is moving around the sun at 33,000 miles per hour, he said, and the sun, located about two-thirds away from the center of the Milky Way (Earth’s galaxy), travels around that center at a half million miles per hour, making one orbit in a half million years.

“We don’t notice it, but it’s true,” he said. “We don’t feel any of it, but we know it’s happening because we can measure it.”

With the large telescopes now available, the largest of which is around 30 feet in diameter, astronomers can see other galaxies, said Vanden Bout, including the big group of galaxies called the Virgo cluster, of which the Milky Way is a part.

“And they’re all spinning around,” he said. “We’re going to get dizzy if we think about it too hard.”

With that, Vanden Bout fielded questions that ranged from the easy ones, such as “How can we see stars?” and “How do shooting stars move?” to the tough ones, such as “How do black holes work?” and “How is a galaxy made?”

He answered each from a lifetime of knowledge in language that most of the young audience appeared to understand.

After the talk, library director Bette Dillehay presented Vanden Bout with the summer program’s signature baseball cap, sporting the phrase, “Science Matters.”