Tue, 09 Jan 2007 08:36 CST
It's a meteor. It's a green flash. Or is it all in the mind?
Intermittent bursts of green streaks across Singapore skies on Sunday evening have set communities abuzz with talk of unidentified flying object (UFO) sightings and experts debating the phenomenon.
The light was seen around 7.40pm in areas including Woodlands, Bedok, Bukit Panjang, Clementi and Marina.
While some readers said it was a green light, others observed a blue and white glow. The light resembled a fireball with a "tail", lasting for a few seconds in the sky before disappearing, they said.
"There was a light flying very fast going towards Sentosa and it was shaped like a rocket," said self-employed businessman Mr Abdullah Yusof, 48, who was at Harbourfront Centre with his family. The phenomenon lasted for less than a minute, he added.
Another reader, 25-year-old software engineer Xu Tao saw three green lights "moving from left to right" from his Clementi flat. His first thought? Aliens.
He said: "I thought it might be a UFO because it definitely looks different from aeroplane lights."
But the experts have a different, more scientific take. Mr Albert Lim, president of The Astronomical Society of Singapore (Tasos) described it as a bolide, or an exploding fireball.
"This is essentially a meteor but it is a hundred times brighter. A normal piece of rock that comes into the atmosphere will burn up and this is known as a shooting star. When bigger chunks come in, they take a longer time to burn up and they drag across the sky," he said.
There are millions of meteors every day but they are hardly seen by the naked eye and their trails are usually short, lasting from half a second to two seconds. Sporadic meteors like the one on Sunday are so random that it is almost impossible to predict how frequent they occur, he said.
He added that since the meteor was heading southwards, it would have probably ended up in the sea.
However, chief executive of the Singapore Science Centre, Dr Chew Tuan Chiong said: "The fact that it occurred around sunset suggests it is likely to be what people call the 'green flash'."
This is caused by the scattering of sunlight by small particles in the atmosphere, which results in different light components.
"The atmosphere acts as a lens and when these colour components are blended correctly, you see the green flash," he explained.
He does not think it might be a meteor as there was no noise reported.
But Tasos' Mr Lim is not convinced.
"Whether there is sound depends on the distance and how intense the explosion is. This occurred after sunset and the green flash does not normally have a trail or last for 10 seconds. I am almost certain that this is a meteor," he said.
The meteorological services department of the National Environment Agency said there was no information on the phenomenon as it was too small to be detected by satellite.