Tag Archives: Gravitational waves

Gravitational Waves

As you may know, 2016 has already turned into a big year for physicists, probably one of the most important of the century. On 11 February 2016, the LIGO collaboration (Laser Interferometer Gravitational-wave Observatory) announced they had detected gravitational waves.

What are gravitational waves? Predicted by Einstein in 1916,“gravitational waves are ripples in the curvature of space-time which propagate as waves, travelling outward from the source”. (Wikipedia). Let’s make it a bit clearer. Imagine the universe as a big flat lake. Put a balloon on that water and you have got a planet. When you move the balloon, a wave is created on the surface of the water. In the universe, this phenomenon is called gravitational waves and needs a tremendous amount of energy to exist.

Gravitational waves
Gravitational waves from http://www.popsci.com/

Despite the determination of scientists, there was no scientific proof that gravitational waves actually existed, that was…until this year. LIGO‘s first operations between 2002 and 2010 did not detect any waves signal, the intensity of the signal that had to be detected being too small. It was then decided to replace the interferometers, the component responsible for the precision of the measures. The new ones were expected to have about four times the sensitivity of the initial LIGO interferometers.

In September 2015, after 5 years of intensive development and investments of $200.000.000, LIGO became Advanced LIGO. On 14 September which is only a few days after the reopening, Advanced LIGO detected a signal from two black holes with masses of 29 and 36 solar masses merging together about 1.3 billion light years away. Let’s take a moment to appreciate what it is we are talking about. 1 solar mass is equivalent to 2 x 10^30 kg with a light year equaling 1 x 10^16 metres. It is indeed a tremendous amount of energy. During the final fraction of a second of the merge, it released more power than 50 times that of all the stars in the observable universe combined. The mass of the new black hole obtained from merging the two was 62 solar masses.

Not only is this a life goal achievement for the physicists who have been working on it since 1980 and the first and only direct proof of the existence of black holes, but detecting gravitational waves was fundamentally different from what had been done previously. Rather than looking at particles or large objects, gravity science looks at “the medium of the universe itself”. That means physicists, and more generally scientists, could have an insight into previously impossible areas to study.

So, what we have here is not just a confirmation of gravitational waves, not just a window into black hole collisions, but a proof that we have at our disposal a whole new form of astronomy.