In a Ted presentation, physicist Allan Adams describes the relevance of the gravitational waves in better understanding the universe. He mentions two black holes collided in a distant galaxy about 1.3 billion years ago, converting the matter equal to three suns into pure energy in a tenth of a second. But the energy from the collision was not released in the form of light but gravitational waves. This collision happened around the same time the earth had become host to multicellular life .
The search for the gravitational waves began about 25 years ago when Rai Weiss at MIT and Kip Thorne and Ronald Drever at Caltech proposed building a giant laser detector to detect the gravitational waves from the colliding black holes. While their proposal was initially met with skepticism by many, the US National Science Foundation decided to fund their idea. The laser detector called The Laser Interferometer Gravitational-Wave Observatory (LIGO) eventually became a reality after decades of brainstorming, research & development, and construction. LIGO is now called Advanced LIGO because it continues to be improved .
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LIGO was turned on in early September 2015 and detected the gravitational waves from those colliding black holes just days later. A gravitational wave is a ripple in the shape of space and time. but the gravitational wave are not easy to detect because they are extremely weak and this is one of the reasons the idea of a laser detector was initially dismissed by many, even if that laser detector now happens to be five km long. LIGO co-founder Kipp Thorne acknowledged in his landmark paper on gravity in 1973 that the laser detector is not an ordinary challenge but he also expressed optimism that such a task may be doable by combining the ingenuity of the physicists and the support of the general public .
LIGO could be understood as an ear instead of an eye. Visible light tend to have a very small wavelength which makes it easier to detect them but the sound wavelength can be as long as 50 feet which poses detection challenges. Gravitational waves cannot help us make images of the things out in the universe but listening to the gravitational wave still helps us better understand the universe. The waves tell stories because the sounds of different events are different. For instance, the gravitational waves from the collision of non-spinning black holes sound different than the gravitational waves from the collision of spinning black holes. The whirring sound of the gravitational waves detected by LIGO in September 2015 allowed the physicists to determine the fact that the colliding black holes had mass of 29 suns and 36 suns, respectively and they were whirling around each other 100 times per second .
LIGO is revolutionary because it provides us a new way of understanding the universe. Instead of seeing, it allows us to hear the universe. This is important because there are limitations to what we can see. For example, much of the action in supernova happens at the core and the core is hidden behind thousands of kilometers of iron, carbon, and silicon. We can never see such things in action because they are opaque to light and similarly, there may be other things in the universe that we will never be able to see. Thus, the ability to listen will allow us to discover things we would never have found otherwise. Last but not least, the ability to listen will help us understand the universe from its very beginning.
- Adams, Allan. What the discovery of gravitational waves means. 10 March 2016. 27 November 2016 https://www.youtube.com
