1.3-billion-year-old space event detected

It is not very often that something gets reported in the newspaper 1.3 billion years after it happened 12 billion trillion km away.

This, however, was felt on Earth in September last year, albeit by sensitive scientific instruments.

Researchers from the Laser Interferometer Gravitational- Wave Observatory (Ligo) in the United States announced in February the detection of waves triggered by the collision of two black holes, which are each about 30 times the mass of the Sun. This was the first time such waves had been measured directly.

These gravitational waves are like ripples on a water surface. In this case, the surface represents spacetime, a view of the universe that merges space and time into a single entity.

The waves had been predicted by Albert Einstein in his general theory of relativity a century ago, but have never been verified until now. This is because gravity is a relatively weak force, requiring both a very large disturbance and a highly sensitive detector to "see" the waves.


The energy released in the 20 milliseconds of the recently documented collision was 50 times that of all the stars in the observable universe. A single star like our Sun has the power of more than 10 billion nuclear bombs going off every second.

Even with that much energy, measuring the gravitational waves wasn't a trivial exercise.

Ligo scientists had devised a set-up that fired lasers along tunnels 4km long. The gravitational waves caused tiny changes in tunnel length, which could be measured in terms of the time the lasers took to travel back and forth.

To detect those changes required an accuracy equivalent to measuring the distance from Earth to the nearest star outside the solar system to within the width of a human hair.

In the comic below, cartoonist and former science teacher Otto Fong gives his take on what the discovery means for those not playing with the lasers.

Mr Fong is the creator of the Sir Fong's Adventures In Science comic-book series.

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A version of this article appeared in the print edition of The Straits Times on April 01, 2016, with the headline 1.3-billion-year-old space event detected. Subscribe