"Nice hamsa!" said the young barista as we passed by the little coffee shop during an overnight ferry from Oslo to Copenhagen.

My wife, Anne, and I were on the second leg of a long-awaited heritage tour of Norway and Denmark last summer that was slowly taking an unexpected Jewish turn for me.

The barista reminded me of a Danish version of our son, Max. He had a straight nose and a long angular Nordic face, dark brown eyes, closely cropped black hair fashionably trimmed on the sides and two days worth of stubble. Anne was wearing her palm-shaped amulet with a blue eye in the center (also known in Islam as the "Hand of Fatima" to ward off the "evil eye") that I had bought her as a gift from Israel. I noticed that the barista wore a silver "chai" ("life" in Hebrew) medallion around his neck.

"Nice chai," I responded, and then told him the hamsa was from Israel.

"So's mine," he smiled back.

That's when I knew.

I reflexively reached under the neck of my shirt and revealed a blue Star of David pendant made of Eilat Stone. "So's mine," I said.

He would nod and smile at us each time we passed his coffee counter, and later he told us his story. He said his mother was a Danish Christian and that his father was a Polish Jew whose family had perished during the Holocaust. He considered himself Jewish, "although the rabbis probably wouldn't accept me."

"You are what you say you are," I told him, feeling a strong sense of paternalism.

"I could say I'm black, too" he countered with a note of resignation in his voice, "but that still wouldn't make me an African American."

"You are what you say you are," I repeated, this time more firmly.

He brightened and as we walked away, I heard him call out, "Kol Ha'kavod!" -- Hebrew for "all the respect."

Lenny Bruce once said, "If you're from New York and you're Catholic, you're still Jewish," during a riff on the differences between being Jewish and a gentile. Growing up in the greater New York area of the 1960s and '70s I, too, thought everyone was Jewish -- especially while living in the heavily Jewish enclave of Great Neck, Long Island. When my teacher at Clover Drive Elementary called out the name David in class, at least six hands shot up. It didn't matter to me whether you were Italian, Irish, Black, Greek; in my world view, everyone was a little Jewish --except for the Swedes, who reminded me of the towheaded, docile futuristic Eloi race in the H.G. Wells-inspired science fiction movie The Time Machine. We were fully assimilated cultural Jews ("Bagels-and-Lox Jews," as my dad liked to say) in the most Jewish populated city in the world, outside of Israel. In New York, you were simply Jewish by osmosis.

I think I inherited this Jewish awareness mentality from my dad. (Attention sociologists: you are free to refer to this cultural phenomenon as JAM.)

My father likes to tell the story of how when we went on a family trip to the south of France in the summer of 1965, we felt somewhat like fish out of water. And then we heard the familiar reassuring songs of Fiddler on the Roof from the chateau of our neighbor, Madame Danielle. I'm not sure if Madame Danielle was indeed Jewish, but enjoying Fiddler made her Jewish enough. All summer long my brother Drew and I would play with her children.

So it came as a surprise when I left for college in Madison, Wis., and discovered I was in the minority. Still, wherever I went I carried with me this invisible Jewish force field that told me there was always someone Jewish. And I have rarely been wrong.

But nowhere was this made more apparent than during last summer's supposed Scandinavian heritage trip for my wife.

Some call it "Jewdar" -- Jewish radar -- a sort of sixth sense that enables Jews to recognize other Jews. On our first night in Oslo, we met Mike and Patty Abkowitz of Austin, Texas, two intrepid travelers originally from western Massachusetts.

We quickly surmised from our surnames our ethnic background, but we still went through the motions of "Jewish Geography." I told them I was originally from New York City, but I was now a photographer of mostly bar and bat mitzvahs, living in Milwaukee. "Then you must know Timo," Mike said, referring to a popular Austin-based DJ originally from Wisconsin. Bingo. In fact, Timo (who is not Jewish) was a good friend of mine whom I'd worked with on about two dozen b'nai mitzvahs in Milwaukee, which practically makes him Jewish. Timo was Mike and Patty's DJ for their children's mitzvahs.

We also met the Alemans, a family of Cuban Americans from Homestead, Florida. Mario, about 75, was a retired Miami VA psych nurse, and his wife, Maria, was a retired nurse practitioner, and their grown-up daughter was still a practicing VA nurse. Mario carried a souvenir of a moose doll holding a Norwegian flag he called "Pepe" around his belt loop. "Pepe is tired," he'd say in his thick Cuban accent, and gently pat his moose on the head after a long day of viewing majestic waterfalls and Norwegian stave churches.

I asked Mario about his last name, which sounded like Allemande, the French word for a German. This seemed an odd name for a Cuban.

Mario told me his story. He said he was a descendant of Marranos -- Jews from the Iberian Peninsula forced to convert to Christianity -- who would flee the Spanish Inquisition, eventually making their way to the New World, settling among a colony of exiled Jews in Havana. After Castro's Communist overthrow, he and his family fled Cuba for Miami, where he would go on to serve as an ARMY medic in Vietnam. After the war, he and his family settled in the Miami area. While the Aleman's did not identify themselves as Jews -- Mario said he was raised in a nonreligious household -- we definitely shared a kinship as though we were indeed distant relatives.

In honor of my wife's late father, Robert Foster, a proud yet humble Norwegian American who built homes for a living, we visited Norway's Resistance Museum on the grounds of the medieval Akershus Castle overlooking the scenic Oslo harbor. The museum chronicled Norway's resistance to Nazi occupation during World War II. My late father-in-law had visited the museum years back and met elderly former resistance fighters who regaled him with tales of firing at Nazis while on skis and disappearing into the Norwegian woods. Sadly, nearly a third of Norway's estimated 2,200 Jews were deported and died in the Holocaust, but a number were shielded by their compatriots and even served in the ill-fated resistance.

In one museum panel, a name jumped out at me: Tor Friedman. Could we be related, I wondered?

Also on our tour was an Iranian family from the Los Angeles area. The grandfather stood stiffly and rarely spoke, and when he did, only in whispers -- a foreign language, most likely Farsi. Although he dressed casually, I sensed from the dignified way he carried himself that he had once held a position of authority, and I could imagine him in a uniform festooned with medals.

His daughter was about 40 and she spent most of her time doting on her 11-year-old daughter. The granddaughter spoke in a tiny adenoidal voice as though she had a stuffy nose, wore sparkly sneakers and colorful jumpsuits and spent most of the time staring into her iPad, playing beeping and buzzing games and snapping pictures.

They traveled with an uncle, about 60, who said he was a photographer in Los Angeles. We would compliment each other on our respective landscape photos on our digital cameras, but we never discussed politics or history, despite my subtle attempts to interject such topics into our conversations.

I suspected that the Iranians were Sephardic -- Jews from the Middle East, unlike Ashkenazic Jews, like me, who came from Eastern Europe -- but they never said so and I had the decency not to ask. They wore no obvious religious articles of clothing or Jewelry that would reveal their ethnicity. It was just a feeling I had, my "Jewdar" once again kicking in.

My wife and I experienced a number of other chance Jewish encounters during our Scandinavian summer adventure. When we boarded the overnight ferry to Copenhagen, the front deck quickly filled with tourists. A polyglot of dialects and languages soon filled the air like odors in a spice shop. I recognized a few words of Spanish, French and German, but had difficulty placing the various Slavic and Asian languages I also heard. As the ferry pulled out of the Oslo harbor, two tanned men with dark hair took a seat next to us. They spoke in rapid-fire succession in what I quickly recognized as Hebrew. An announcement came over the loudspeaker: would a "Shlomo" and an "Avi" report to the front office. The two men stood and left the deck.

As we made our way along the busy Vesterbrogade artery that cuts across the main shopping district of downtown Copenhagen, we passed the entrance to the famous Tivoli Gardens, and once again I heard the familiar guttural sounds of Hebrew like a radio broadcast from Israel. I pivoted and spotted a fashionably dressed woman lugging shopping bags, conversing on her smartphone. For a moment I felt I was on the teeming streets of Tel Aviv.

On the final day of our trip, we visited the Frederiksborg Castle museum outside of Copenhagen, the formal royal residence of the Danish nobility. We entered a room filled wall-to-wall with royal crests signifying different family allegiances and honorifics dating back to the 17th century, when I discovered a crest with the familiar six-pointed Star of David.

So did the 11-year-old Iranian girl, whose eyes lit up. She snapped a close-up of the Star of David on her iPad and ran back, excitedly, to show her mother, who just smiled and gently placed her arm around her daughter's shoulder. And then I knew for certain.