On Saturday night, there was a loud explosion-like sound from many parts of Helsinki, but the source of the explosion remained a mystery on Monday.
The boom sparked a discussion on social media The residents of Oulunkylä, Kumpula, Käpylä, Arabia, Kulosaari, Metsälä, Meilahti and Kulosaari claim to have heard noise on Saturday at about 11.45 pm.
Speculation about the sound source has also been widespread. Some have suggested that it could have been a meteor that has struck the atmosphere, an earthquake, or even a supersonic explosion caused by an air force fighter jet. However, these possibilities have been ruled out.
Helsinki police began receiving notifications from residents of the Oulunkylä area shortly before midnight. People described noise a "hollow exploding sound" and "big shot."
The police unit was sent to Oulunkylä, but the police did not find a reason to explain the sound.
Meteor, earthquake, war games were ruled out
Ursa from the Group Amateur Astronomy Association also investigated the possibility that the noise was due to a meteor event. However, based on the images taken by the group’s camera network, there have been no indications so far that the sound came from a meteor, Ursa’s spokeswoman said. Anne Liljeström.
"The current opinion is that it was probably not due to a meteor, but of course it cannot be ruled out." he said.
The hard boom was also unrelated to military operations, Army Office Communications Manager Max Archipelago told Helsingin Sanomat.
He told the newspaper that there was no military aviation activity at the time that could have caused it.
Some have also wondered whether the explosion could be related to the ongoing Zapad military exercises in Russia and Belarus. However, Arhippainen said that it would be difficult to imagine it because the exercises were held so far from Helsinki.
Others have speculated that a mysterious voice could have come from a seismic event like an earthquake. Seismologist from the University of Helsinki Tuija Luhta, said that probably didn’t happen.
"It was probably not an earthquake of any kind. We have an even more detailed analysis from that day [to examine]but we looked at it quickly over the weekend and it doesn’t show clearly [seismic activity] at our stations in Helsinki," Luhta said.
"If it were an earthquake, it would occur mainly in large seismometers and would have been heard" he said, adding that this was not the case.