Oh, the things Bruno Frohlich can scan.

Ancient whale skulls. Smashed human ones. Stradivarius violins. Violas. Cellos. Guitars. Stringed instruments from Mongolia. Apollo spacesuits. Eagle feathers. Mummified birds from Egypt oddly missing their heads. Dinosaur leg bones, fossilized. Thigh bones, hip bones, arms bones, teeth. An infant’s iron casket dug up in the District. Live turtles. Dead crocodiles. Mummy after mummy from Egypt. And one from Peru.

The Smithsonian Institution owns 137 million things. Over the past 15 years, Frohlich, it seems, has scanned them all.

Okay, not quite. But if he had enough time, he would.

“This is my hobby,” Frohlich says of his job.

In 1996, Siemens Corp. donated a used medical CT scanner to the National Museum of Natural History. Understanding the machine’s potential to reveal ancient secrets, Frohlich took charge of it.

“In the old days, 20 years ago, we would do an autopsy, cut the body open,” Frohlich says of studying mummies. No need for such destructive science now. Just scan an object, and a three-dimensional image of its innards appears.

Frohlich said few other museums own full-size CT machines. And now the Smithsonian owns two. A faster, higher-resolution scanner arrived in September, again a used model (again donated by Siemens) that retails for about $250,000. It’s a gleaming white five-foot-tall vertical doughnut with a sliding table attached, squeezed into Frohlich’s third-floor laboratory.

In a hospital, the scanner’s penetrating X-rays might spot a tumor. At the museum, they reveal that what appears to be a small mummy of a sacred kitten is, in fact, hollow — a 2,500-year-old Egyptian con job.

“You never know what you’ll find,” says the 60-something Danish native, perhaps a little impishly.

A small rectangular box hangs above the lab door. It reads “X-RAYS” and flashes red when the scanner is on. People walk in anyway, interrupting. This annoys Frohlich. There’s so much to scan.

Frohlich enjoys the solitude of it. “I’m not a give-me-attention kind of guy,” he says as he briskly leads a visitor past a mob of tourists in the museum’s entrance hall. “I’m more of a leave-me-alone type.”

Sometimes this happens: A colleague wheels up to the lab a behemoth chunk of dinosaur skeleton. It is mineralized bone — a fossil — so it is hard. X-rays scatter off such items, bouncing all over the joint and possibly exposing the unwary to tiny doses of radiation. So when confronted with hard targets, Frohlich waits until everyone in the vast museum has left.

In the 2 a.m. quiet, he scans.

“My workdays keep going; they are 24 hours,” he says. “I love it.”

Scanmaster of the Smithsonian is Frohlich’s second job at the museum. He arrived in 1978 as a forensic anthropologist, a career that still carries him around the world. In the Aleutian Islands of Alaska and the deserts of Mongolia, he helps solve ancient murder mysteries. When he’s not traveling, he spends half his time in Vermont, where he aids the state police there and in Connecticut in solving more-recent homicides.

At the museum, though, it’s all about the scans. As Frohlich works, he sits behind a leaded-glass window with a view of the CT machine. A dosimeter stays clipped to his shirt pocket, measuring his radiation exposure.

The CT machine whirs in a wash of white noise. On the screen of the control station, a three-dimensional image appears, a high-resolution peek inside rock, or metal, or wood, or tissue. It’s technology; may as well be magic.

Coming back to life

One recent morning, the museum showed off its new scanner. Three reporters, a TV camera and four high school interns clad in red polo shirts crowd around the scanner table. It’s warm. Sweat appears on Frohlich’s brow. As he expounds on the machine’s value to science, he talks a little too fast, excitedly.

As he does so, a 700-year-old Peruvian rests on the scanning table. She is on her side with her legs crossed, one knee sticking up. She is tiny. She has seen better days. Her bones are bony. She is missing a lot of teeth and some of her skin. Ragged cloth strips still wrap her head. Decades ago in the Andes, she was found in a cold, dry cave, good for preservation. She’s a natural mummy.

Scans revealed that the woman was in her 40s when she died, her organs still intact. She may have been a sacrifice, Frohlich says. Other scientists can now read the images and learn more about the woman’s health, search for hints as to what diseases she may have had, whether she had any broken bones. They can piece together her story.

As Frohlich talks, a phalanx of Siemens executives and the museum’s director, Cristian Samper, wait in the hallway. They are on a schedule. Someone tells Frohlich to wrap it up.

“They expect me to describe 20 years of work in 20 minutes,” he scoffs.

He keeps talking, faster.

He pulls a human skull from a shelf behind him. Yes, there are human skulls on his shelves, in cardboard boxes numbered 39, 233, 787. The Smithsonian flies Frohlich to Mongolia frequently to collaborate with the Mongolian Academy of Sciences. And so, here is a skull he brought back.

Frohlich turns it over, points to a triangular hole gaping in the rounded back of the skull. Something like a baseball bat could have done it. A real good thwack. Who killed this centuries-old Mongolian, and why?

“We’re not out there just to pick up mummies and skeletons,” Frohlich says later of his expeditions. “We’re there to learn about the people. We make them come alive.”

Scanning helps. It can show, for instance, whether bone healed after a trauma, indicating survival. The hole-in-the-head guy, he did not survive the whack. His face is smashed, too. “Someone made sure he was dead,” Frohlich says.

The sounds of music

Frohlich enjoys the forensics, unraveling these mysteries. Even more, he loves scanning.

After the first machine arrived, Frohlich sent word to staff at the Smithsonian’s 19 museums and galleries: Bring me your scannables. And so they did.

Some Air and Space Museum curators carried over a spacesuit once worn by a moon-walking astronaut. The scans revealed weak spots in the suit’s latex and neoprene, guiding conservation efforts.

National Zoo herpetologists brought him a turtle.

The reptile kept trying to amble off the table. Frohlich set it atop a block of plastic foam. “The arms and legs were flapping,” Frohlich says, demonstrating with his own arms and legs.

Why scan the turtle? Was something wrong with it? “Yeah, I guess” is the answer. Diagnosing the ills of a turtle is not the point for Frohlich. The point is to scan it.

So the machine virtually sliced the turtle into hundreds of paper-thin digital slices. It is now a digitized turtle, stored in the cloud somewhere.

While the Smithsonian owns all of the scan data, Frohlich is working to make it publicly available. By March, he says, visitors to a new Web site will be able to download nearly every scan.

Such as that of a famous violin.

About a decade ago, someone at the National Museum of American History arrived with a Stradivarius violin.

“I thought it would be a half-hour project,” Frohlich says. But he became fascinated with the famous instrument. “It’s been 10 years.” His blue eyes go wide when he says this, as if even he is incredulous.

Frohlich set out to determine if a heartless X-ray machine could suss out the sonorous secrets of a Stradivarius.

Eventually, his scans built three-dimensional maps of 11 Stradivarius violins, violas and cellos. Their innards were revealed in such high resolution that Frohlich could see tiny wormholes in the wood. The scans also showed that the Italian who fashioned the instruments in the 17th and 18th centuries, Antonio Stradivari, used very thin wood, perhaps a clue to their tremendous timbre.

But even after all this, Frohlich is convinced that scanning will never reveal why a Stradivarius sounds like a Stradivarius. Music is largely in the ear of the beholder, he says, pointing to his ear.

In a research paper describing the project, Frohlich and three colleagues wrote, “Did [Stradivari] apply some secret features, material and/or chemical treatments to his instrument, which later instrument makers failed to recognize? Did he use special treated wood, special varnish, and did he select wood with very specific density to enhance both the looks and the tone qualities? Or, is it all a product of manipulative marketing in order to sell more instruments? We still do not know for sure, but it is most likely a result of many factors, some known to us, and others still a secret.”

The enduring mystery has not stopped instrument makers from trying to re-create a Stradivarius. Two luthiers in Minnesota recently used CT scans to attempt to replicate one of the violins, called the Betts, now held by the Library of Congress.

Frohlich says they have little chance of reproducing the sound quality.

Still, he’ll keep scanning.

“Can you do that fish fossil this afternoon?” one of the museum’s paleontologists, David Bohaska, asks as he wanders into the lab.

Although it pains him, Frohlich cannot. But he will soon. “How about next Monday?”