Putting a number on displacement is a tall order, but we do have an idea about who is leaving Oakland.

Produced and edited by Olivia Allen-Price, Vinnee Tong, Paul Lancour and Julia McEvoy. Theme music by Pat Mesiti-Miller.

Ask us a question at BayCurious.org.

Follow Olivia Allen-Price on Twitter @oallenprice.

Bay Curious listener Kristin Seitz was looking at a map of San Jose when she noticed an awful lot of holes. The city's territory isn't one undivided shape, but rather resembles a piece of Swiss cheese. Seitz wondered: Why are there so many unincorporated "urban islands" in the San Jose area?

Reported by Ericka Cruz-Guevarra. Produced and edited by Olivia Allen-Price, Vinnee Tong, Paul Lancour and Julia McEvoy. Theme music by Pat Mesiti-Miller.

Ask us a question at BayCurious.org.

Follow Olivia Allen-Price on Twitter @oallenprice.

Owners of historic buildings might be able to sell the air space above their building, allowing developers elsewhere to build higher.

Listener Jenny Wread has noticed the Bay Area's smog on her commute. And she's hearing more Spare the Air alerts. How is the air quality doing in the Bay Area as the population grows?

Reported by Matt Beagle. Produced and edited by Olivia Allen-Price, Vinnee Tong, Paul Lancour and Julia McEvoy. Theme music by Pat Mesiti-Miller.

Ask us a question at BayCurious.org. Follow Olivia Allen-Price on Twitter @oallenprice.

Take a trip around the San Francisco Bay and get to know our local foghorns -- where they are, how they work, who turns them on.

Reported by Laura Klivans. Bay Curious is made by Olivia Allen-Price, Jessica Placzek, Paul Lancour, Ryan Levi and Suzie Racho. Additional support from Julie Caine, Julia McEvoy, Ethan Lindsey and Howard Gelman. Holly Kernan is Vice President for News. Theme music by Pat Mesiti-Miller. Ask us a question or sign up for our newsletter at BayCurious.org. Follow Olivia Allen-Price on Twitter @oallenprice.

If you live in the Bay Area, a foggy day can be a good excuse for some guilt-free time indoors. If you live near the water, days like that bring something else: foghorns.

Reported by Laura Klivans. Produced and edited by Olivia Allen-Price, Vinnee Tong, Suzie Racho, Paul Lancour and Julia McEvoy. Theme music by Pat Mesiti-Miller.

Ask us a question at BayCurious.org.

Follow Olivia Allen-Price on Twitter @oallenprice.

In the 1960s, San Francisco was in the midst of a sexual revolution. Officials across the Bay in Oakland wanted none of it.

Reported by Adizah Eghan. Produced and edited by Olivia Allen-Price, Vinnee Tong, Paul Lancour, Suzie Racho and Julia McEvoy. Theme music by Pat Mesiti-Miller.

Ask us a question at BayCurious.org.

Follow Olivia Allen-Price on Twitter @oallenprice.

When Sutro Tower was first proposed, nearly everybody hated it. How did it get built?

Reported by Jessica Placzek. Produced and edited by Olivia Allen-Price, Vinnee Tong, Paul Lancour, Suzie Racho and Julia McEvoy. Theme music by Pat Mesiti-Miller.

Ask us a question at BayCurious.org.

Follow Olivia Allen-Price on Twitter @oallenprice.

The Big Apple, Sin City, the Big Easy -- all famous nicknames for American cities. But have you heard of Man Jose? This week we explore if San Jose should be called Man Jose.

Reported by Jessica Placzek. Produced and edited by Olivia Allen-Price, Vinnee Tong, Paul Lancour and Julia McEvoy. Theme music by Pat Mesiti-Miller.

Ask us a question at BayCurious.org.

Follow Olivia Allen-Price on Twitter @oallenprice. And use the #BayCurious hashtag!

f you’ve walked past Adobe’s corporate headquarters in downtown San Jose, you may have spotted them: four big orange LED lights that look like flat-head screws, turning in apparently random patterns.

This week’s Bay Curious question comes from listener Geoff Morgan, who wanted to know:

What do the turning wheels on the top of the Adobe building mean?

To start with, it helps to know Adobe makes computer software for people who work with words, pictures and sound.

“At the core of our DNA, really, is art and technology,” says Siri Lackovic, the company’s senior brand strategist.

That’s why you’ll find clever art installations all over their office towers.

Siri is one of the two people on the planet who know the whole story behind the glowing orange orbs Geoff noticed. The other person, of course, is the guy who came up with the concept, New York artist Ben Rubin.

“The hope is that someone would look up and say: ‘What is that?’ ” Ben says. “What is that thing trying to say, you know? What is its message?”

The name of this installation is San Jose Semaphore.

“Semaphore, by definition, is really a form of visual communication,” Siri explains.

Way back when, the only way to communicate surreptitiously over a short distance — say, from land to a ship — would be to rely on flag bearers.

“They would hold up the flag, and depending on the position of the flag, would let them know if it was safe to come in, or better to stay put,” she says.

This resonates with Geoff, the KQED listener who asked the question.

“I actually was in the Navy, and so I remember people communicating with flags, and it was always interesting to me because it looked very official, but a lot of times, they were talking about the latest baseball scores from ship to ship and things like that,” he says.

In case you didn’t serve in the Navy, here’s an amusing set of dramas executed in semaphore by Monty Python.

So, the short story on San Jose Semaphore is that it’s an art installation. The long story stretches back to artist Ben Rubin’s childhood in Boston during the 1970s. Back then, he owned a Heathkit shortwave radio. Sometimes, when he turned it on, he’d hear the strangest things.

“These sort of clicks and beeps and mechanized announcements,” Ben says. “Who could not listen to an encrypted message and not wonder what it says, you know?”

As NPR reported in a 2000 feature for the “Lost and Found Sound” series, these were numbers stations, shortwave radio broadcasts that historians believe transmitted messages to spies stationed around the world, starting in World War I.

To the average listener, the letters, numbers and songs broadcast on the stations sound random. But if you have the key to decode the gobbledygook — it’s a message.

Ben was fascinated by these numbers stations. So when it came time for college, he got a bachelor’s degree in computer science and semiotics, the study of signs and symbols. After graduation, he starting making art inspired by his studies. Now he makes media installations using technology, sound, images and physical structures — like the piece on the top of Adobe’s building in San Jose.

Silicon Valley Loves A Challenge

Each of these orange discs can assume four positions: horizontal, left-leaning diagonal, vertical, right-leaning diagonal. Four positions, plus four discs, means there are 256 possible combinations.

Every 7.2 seconds, those wheels turn to a new configuration of sort of positions. Then they rest.

“When they’re in that resting position,