People living 100 miles apart in the United Kingdom were left baffled when they heard mysterious "bang sounds" between 10 p.m. and 10:30 p.m. on Saturday.
The "mystery bangs" were so loud that windows shook. Scores of people from London to Glasgow said that they had heard the bangs that sounded like that of fireworks or loud aircraft, Mirror reports.
Some people even suggested that the sounds might be of "aircraft sonic booms" coming from Russian airships, which have performed "routine military exercises" in the past while passing through the area.
Twitter user, @Keelingover, posted on the social networking site: "Prob RAF scramble, we're back to Cold War tensions." He thought the Russians may have been flying close to British airspace.
Another user also echoed similar thoughts; @VirtualAstro was convinced that the source of the sounds was an aircraft. "My dogs are freaking out! Gotta be sonic booms or something if heard over such a large area by so many," the user tweeted, Metro reports.
However, the Ministry of Defence denied such claims and told the Daily Mail that they had no information on any jets flying over the area. Meanwhile, the Metropolitan Police said that the only possible explanation to the sounds would be a firework display in Croydon. But, people do not believe it as the sounds were very distinct as far as Glasgow.
Dr Bhupendra Khandelwal, who is an engineering research associate from Sheffield, says the sound can be from a 'pulse detonation engine'.
A resident from Croydon in South London recorded the sounds on her phone and posted it on the internet. It can be heard in the video below:
"It makes the same kind of pulsing sound as the one on this audio. When we run a test engine it's a real industrial noise and you can hear it for miles. We have people coming to us asking to make less noise or keep it to the daytime," Khandelwal said.
But, what is crucial here is that the engine works by using the force from a series of explosions, caused by mixing a fuel mist and air intake to thrust itself forward. It is believed that it can power planes at five times the speed of sound. So, does that mean the bangs were produced from explosions somewhere near the region and someone is trying to generate power for some unknown use?
Some said that similar sounds were heard in New York as well.