Andrew Zentner

Andrew Zentner

No, “The Big Bang Theory” wasn’t always a TV show.

And as far as Andrew Zentner is concerned, the nearly century-old explanation for the origin of the universe pretty much is tantamount to fact.

The professor in the University of Pittsburgh’s Department of Physics and Astronomy will admit one of his pet peeves is telling people what he teaches and studies, and getting responses along the lines of: “Oh, that’s just a theory.”

“They have no idea of what level of detail we know about all of this,” he told those attending the “Our Universe: the Past 13.8 Billion Years” program he presented July 1 at Mt. Lebanon Public Library.

“Saying something is just a theory is not even a meaningful criticism, because everything you know is a theory, whether or not you’re willing to admit it,” he said. “The question is: is there evidence to support the theory?”

As a theorist with particular interest in cosmology, the science of the origin and development of the universe, Zentner has seen the continuing expansion of the capabilities for gathering observational data, and those in turn have gone a long way toward corroborating many of the hypotheses related to the field.

For example, the age of the universe can be determined by analyzing the spectra, the colors produced, of the farthest objects detectable from Earth.

“When you take a spectrum, the elements in the periodic table and the molecules all absorb and emit light,” he explained. “But they only absorb and emit light at very specific colors, very specific wavelengths and frequencies.”

The remote objects show a composition of almost entirely hydrogen and helium, the elements with the two lowest atomic numbers and the first to form, 20 minutes or so after the event that launched the universe. Elements with higher atomic numbers, including carbon and oxygen, formed within the matter that became stars, and the ages of the newer objects can be determined by the presence of heavier elements in their spectra.

Regarding the universe’s origin, a Belgian priest, mathematician and physics professor named Georges Lemaître proposed in 1927 what became known as the “Big Bang Theory,” that everything began as a single point of unimaginably high-density matter.

Two years later, American astronomer Edwin Hubble provided support for the theory by observing the farther galaxies are from Earth, the faster they tend to move away, which indicates the universe is in a continual state of expansion.

Some galaxies are 12 billion light years distant, which adds up to a number of miles with 21 zeroes at the end.

“The light that galaxy emitted that we’re collecting today was already traveling for 2 billion years when the Milky Way formed,” Zentner said about our galaxy. “It was already traveling over 7 billion years when the Solar System formed.”

Contrast that to the distance to the nearest star to Earth, in the Alpha Centuri system, which is some 25 trillion miles away. That’s about where light years start to come in as the handiest form of measurement.

“The light that leaves this star, Proxima Centauri, takes four years to get to us, and that’s when we observe it,” Zentner said. “This is still like nothing in the grand scheme of things.”

Consider that the Milky Way has a diameter of 100,000 light years, and the next-closest major galaxy, Andromeda, is 2 million light years distant.

And consider the universe contains perhaps 50 billion galaxies, each containing hundreds of billions of stars, plus all the planets and everything else revolving around them.

No wonder Zentner has some advice for anyone who wants to study astronomy.

“Learn math,” he said.

Multimedia Reporter

Staff writer Harry Funk, a professional journalist for three-plus decades, has been on the staff of The Almanac since 2015. He has a bachelor’s degree in journalism and master of business administration, both from Indiana University of Pennsylvania.

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