The mystery boom in the wee hours Saturday was a literally moving experience for Bryan Adlam.

"I heard the boom — it was quite loud — but I also felt it. I felt my house move," said the real estate agent, who lives in the Crown Point neighbourhood near the escarpment.

Turns out bewildered residents across the city heard the same thing after 2 a.m. On the beach strip. The Mountain. Even Ancaster.

Adlam posted a question about the sound blast on Facebook that quickly spawned 500-plus comments, theories and, obviously, fart jokes.

But so far, the source of the thunderous bang remains a mystery.

Was it a supersonic jet? An industrial accident? A skyquake? Nobody seems to know.

The most popular online theory — a dropped container of molten steel or slag — was emphatically shot down by steelmakers Stelco and ArcelorMittal Dofasco.

"We've checked twice. There was nothing," said ArcelorMittal Dofasco spokesperson Marie Verdun.

She acknowledged the oft-repeated online suggestion that workers accidentally "dropped a ladle" — think an enormous steel-plated vessel full of molten metal, ponderously carried through the air by crane.

Yes, Verdun said, that would be loud. "But if we dropped one, we would have a much bigger problem than a big noise," she said.

It's always possible another industrial accident was to blame, but neither police nor fire were called to an incident large enough to be heard across the city.

Similarly, no crashes, gas or transformer explosions were reported. (Film production on Ottawa Street this week could involve loud noises, but city officials were not aware of any explosive moviemaking at 2 a.m. Saturday.)

It was also a quiet night for the Hamilton Port Authority and the city's international airport. But spokesperson Tomas Cleary conceded the airport would not necessarily be informed if military jets were in the vicinity, for example.

A sonic boom that rattled the windows of Essex residents in the U.K. two days ago was recently confirmed to be the result of a Royal Air Force jet, according to the BBC.

The Canadian Department of National Defence was still checking Monday to see if military activities over Lake Ontario could have caused Hamilton's mind-boggling boom. Stay tuned.

Neither Canadian Pacific nor Canadian National Railway were aware of any crashes or major incidents on the mainline railways or shunting yards in the city, officials told The Spectator.

We're also "out of luck" for loud weather, said Environment Canada meteorologist Peter Kimbell, who searched all around Lake Ontario unsuccessfully for potential thunder or lightning culprits.

Earthquakes Canada showed no measurable seismic activity at nearby monitoring stations. Local seismographs can record even magnitude 1 tremors — which people typically do not feel — which suggests the boom did not originate underground.

(Interestingly, seismographs did record an "acoustic blip" during a similar wee hours mystery blast in 2005 that befuddled east end and beach strip residents. No one got to the bottom of that boom, either.)

In the meantime, residents have cheerfully filled the informational void with a range of educated-to-wild guesses, including asteroids, solar radiation storms, aliens and "God's taco night."

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But until we hear otherwise, feel free to call Hamilton's mystery blast a skyquake — the default label for unexplained booms out of the blue.

mvandongen@thespec.com

905-526-3241 | @Mattatthespec