Gravitational waves are a modification of the structure of space-time in the universe, due to the interactions of a particular type of star, called the Neutron Star, when orbiting as binary pairs (see Figure 1):
“In 1993, astrophysicists Russell Hulse and Joseph Taylor received the Nobel Prize in Physics for their 1974 discovery of a binary pair of neutron stars (PSR1913+16) 21,000 light years from Earth. Seven years later, after tracking the radio emissions of one star in the pair over a period of years, Taylor and two other colleagues (Joel Weisberg and Lee Fowler) noted that the time it takes for the two stars to orbit each other was decreasing exactly in a way that general relativity predicted if the two stars were radiating gravitational waves. Analyses of other binary neutron star systems confirmed this effect firmly concluding that gravitational waves were not just theoretical. More than 40 years later, on September 14, 2015, gravitational waves were finally directly detected by LIGO's interferometers. This accomplishment was achieved because LIGO is designed to sense the infinitesimally faint whispers of gravitational waves through the imprint of that radiation on laser light. How faint are these whispers? LIGO must detect a change in arm length of about 10-19 m (10,000 times smaller than a proton). Achieving this degree of sensitivity requires a remarkable combination of technological innovations in precision lasers, vacuum technology, and advanced optical and mechanical systems.” (Source: Ligo Caltech educational)
Gravitational waves are a very important physical phenomenon which may help scientists to look at the structure of the Universe with more information and unprecedented details about the “big bang” theory. Until now, the studies about the birth and the structure of the universe have been done mainly by studying light emissions, which is estimated to have started from 300,000 years after the “big bang”. Now the gravitational waves represent a new instrument to study and reveal phenomena that have never been revealed like the “big bang” itself, because this type of effect is related to the collisions of planets, stars across the universe, and hence these gravitational waves may carry information about the initial interactions that caused to the birth of the universe.
How is a gravitational wave detected?
Laser technology is the basis for the workings of LIGO observatories: a laser beam has the speed of light (c=3 x 108 m/s) which is a reference constant all across the universe. If a gravitational wave impacts the tunnel of the LIGO, its length will be modified accordingly and the time elapsed by the laser light to travel through the tunnel can be measured. The indirect measurement of the variation of length of the tunnel will give information about the presence of gravitational waves. Furthermore, the LIGO website shows a scheme for a homemade kit for vibration detectors based on the realization of a Michelson Interferometer, which is able to measure the relative movement of two light sources like a pair of coupled stars (see Figure 2):
The Layout of a Michelson Interferometer (Source: LIGO Laboratory)
The laser realization is a further example of the possible usages of electronics technology to empower astronomy observatories, as is shown by the following figure that contains the description of the ICs for the realization of a green laser pointer:
The schematic of a green laser pointer, built by means of electronics components. (Source: img.bhs4.com)
Do you think that the discovery of gravitational waves will change our perception of the structure of the universe? Do you work with laser technology?