Sai Rayasam, Physical Science, Summer 2020
Caption: Numerical simulation of two merging black holes performed by the Albert Einstein Institute in Germany. This rendition shows the degree of perturbation of the spacetime fabric, the so-called gravitational waves, through the colors (red being the highest degree of perturbation and violet being the lowest degree). (Source: Wikimedia Commons)
In 1916, Albert Einstein predicted the existence of gravitational waves on the basis of his general theory of relativity. He posited that all objects with mass(i.e. humans, cars, and airplanes) create gravitational waves when they accelerate. These gravitational waves are ripples in spacetime similar to how a rock creates ripples in a pond when tossed in. But most objects on Earth are non-massive and far too unenergetic to create waves big enough to detect. As a result, Einstein suggested that we would have to look for extremely energetic and massive processes occuring far outside of our solar system to find these waves (an example of such a process would be a merging black hole).1 However, even these hugely energetic processes only created miniscule waves, which made Einstein himself believe that we would never directly come in contact with them.2
But, in 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) picked up a distortion in the fabric of the cosmos that stemmed from the collision of two black holes more than a billion light years away. This marked the first time that scientists had the technology to be able to directly detect the presence of gravitational waves. However, to detect such a miniscule wave, which was only one ten-thousandth the width of a proton, LIGO’s size and reach needed to be immense. It required installing two interferometers(one in Hanford, Washington and another in Livingston, Louisiana) on opposite sides of the country(to rule out false signals) that would take up four kilometers of area each.2 To address this problem, a team of physicists proposed a plan that would replicate the function of the enormous interferometers and also make it accessible in a device that is only one meter long–4,000 times smaller than LIGO. However, to create such a small device that performs this task would be “phenomenally difficult to build,” says Gavin Morley, one of the co-authors of the study.2
The physicists call the complex theoretical device solution the Mesoscopic Interference for Metric and Curvature (MIMAC). The complexity of the design that Gavin Morley outlines stems from the fact that the key component of the device would be a diamond particle that is around a millionth of a meter. With this diamond particle, the researchers attempt to utilize a quantum phenomenon called superposition, a state where a particle occupies two different positions simultaneously. To achieve superposition, the physicists would beam a series of microwaves at an electron in the diamond, and due to remarkable rules of quantum theory, the electron would both absorb and not absorb one of the microwave photons, therefore occupying two states. One of these states is magnetically neutral and the other has its own magnetic field, so by applying an external magnetic field the physicists can separate the two states of the superposition and then realign them in a predictable way. Any gravitational wave that passes over the detector would disrupt this electron, thereby stretching the shape of its superposition and preventing the components to realign properly. The measurements of these distortions of the superposition would yield the results that illuminate the gravitational waves.2
But this is only a conceptual framework and has not been verified by experimentation. Those specific steps that the physicists need to perform, from the size of the diamond particle to the specific microwave targeting, are what make the device so difficult to build. However, if this device were to come to life, the implications would be vast. Due to MIMAC’s small size, it can be pointed at any direction in the sky, unlike LIGO which is oriented based on Earth’s rotation. Furthermore, any lab in the world could get their hands on it, which would be a huge advancement from the limited two locations that LIGO works at. Also, once the first MIMAC is created, it would be very easy to reproduce, allowing scientists the ability to detect any physical object in the universe that otherwise would have been obscured(due to the fact that gravitational waves do not get altered by matter).2,3 While these implications would sharply increase the number of devices aiming to detect gravitational waves, there is some concern that these advances are far into the future. But experimental physicist Ron Folman believes that it “may be realized within our lifetime.”2 It is indisputable that once MIMAC becomes reality, it would transform the field of gravitational-wave astronomy.
Sources:
- LIGO Caltech. (n.d). What are Gravitational Waves?. Retrieved from https://www.ligo.caltech.edu/page/what-are-gw
- Folger, T. (2020, June 30). Tiny Gravitational-Wave Detector Could Search Anywhere in the Sky, Scientific American. Retrieved from https://www.scientificamerican.com/article/tiny-gravitational-wave-detector-could-search-anywhere-in-the-sky/
- LSC. (n.d). Introduction to LIGO and Gravitational Waves. Retrieved from https://www.ligo.org/science/GW-Potential.php