Updated: Oct 8
Author: Samiha Sehgal
In February this year, my friends and I visited the Vigyan Samagam – a mega science exhibition at the National Science Center in Pragati Maidan, New Delhi, India. Our main intention to visit the center was to see the exhibit of LIGO India, which was one of the major attractions and a proud moment for our country, showcasing the advancements in science, technology and research. Among others, were the Thirty Meter Telescope, India-Based Neutrino Observatory, CERN and a few experiments of its particle accelerator, LHC.
The Laser Interferometer Gravitational-Wave Observatory, or LIGO, is a setup to detect gravitational waves, which were predicted by Einstein in his general theory of relativity.
According to Einstein, when two bodies orbit each other, a special effect is created, and such a movement can cause a ripple in space. These ripples spread out, in the same way that ripples in water are formed when a pebble is thrown into it. These special ripples of space were given the name: “gravitational waves”.
Gravitational waves are invisible, yet incredibly fast as they travel at the speed of light. These waves squeeze and stretch anything (space) that come in their path. This has been explained in the form of an illustration in Fig. 1.
Fig. 1: Illustration of how mass bends space. [Source: NASA.]
The process of laser interferometry is used by the detectors to measure these ripples in spacetime. Gravitational waves are formed by colliding black holes, neutron stars, or by supernovae.
The detailed structure and functioning of the laser interferometers and detectors can be seen from Fig. 2.
Fig. 2: Laser Interferometers and LIGO detectors.
Currently, there are two major interferometers of LIGO in the world, both of which are in the USA. The first is in Hanford, Washington and the second is in Livingston, Louisiana. A breakthrough was made on the fourteenth of September 2015, when the first gravitational wave was detected by LIGO Hanford and Livingston. This observed gravitational wave signal was formed by the collision of two humongous black holes, 1.3 billion light years apart from each other.
A gravitational wave is created by the interaction of objects that are far from the Earth and so, it emits an extremely weak signal by the time it reaches our planet. It is quite difficult to precisely locate its source in the sky, given that the noise (due to the amplifier, receiver, etc.) created by the instruments is much louder. Therefore, sensitive and powerful devices must be used for this purpose, along with advanced mathematical techniques.
A detailed description of the astronomy of gravitational waves has been given in the form of the following Fig. 3, as taken from the exhibit itself.
Fig. 3: Gravitational waves and their astronomy.
(Stephen Hawking’s books were a great way for me to understand black holes and gravitational waves in a lucid manner and can be read by all).
As has been mentioned above, the first two major LIGO facilities are both in the USA. There are a few smaller ones as well in other parts of the world. Fig. 4 shows the geographical location of the LIGO observatories.
Fig. 4: Location of all the LIGO facilities. [Source: LIGO Caltech.]
The image above shows an “approved” facility of the LIGO detector in India. It is indeed a matter of great pride for our nation that the third major facility is being set up in Maharashtra, India.
Fig. 5 describes all about LIGO India – the need for a third major setup, how and why this particular site was chosen, and also how LIGO India will be beneficial.
Fig. 5: LIGO India.
The LIGO India setup will be developed by the Department of Atomic Energy and the Department of Science and Technology of the Government of India, in collaboration with the National Science Foundation, USA. Several other national and international research/academic institutions will be a part of this project.
The volunteers at the exhibit were extremely helpful and explained the project to us in great depth. They had even built a simulator of the interferometer to showcase its functioning and demonstrate the concept. A small part of this model has been shown in Fig. 6.
Fig. 6: If we treat spacetime like the surface of water, then gravitational waves can be considered as ripples on the surface. Water in the model is used to show two black holes, with their characteristic “spin” orbiting each other and merging.
Overall, the LIGO (India) exhibit was highly informative and inspiring. The highlight of this exhibit was to know that India will play a major role in detecting and studying gravitational waves with LIGO. It just shows how far India has come in the field of science and research and has a long and exciting way to go.
The European Organisation for Nuclear Research, or CERN, as it is commonly known as, runs and operates the largest particle physics laboratory in the world. CERN makes use of some of the most powerful scientific techniques (particle accelerators and detectors) to study fundamental/elementary particles.
We all know that our Universe came into existence from the Big Bang. During this process, a huge amount of energy was involved, which in turn, created particles. And thus, did we see the beginning of space and time. The Universe has now been expanding and cooling. It took many years for the first atoms to be formed. And so formed matter. Today, the building blocks of matter and the forces of their interactions are all described by a single theory - the Standard Model. The Standard Model explains the elementary/fundamental particles which go beyond atoms. Now, our regular optical telescopes cannot see beyond the formation of atoms. Particle accelerators are needed to study intricate particle behavior and formation. And their intense energy conditions involved in particle collisions helps us investigate this, and further, how the Universe subsequently evolved.
An interesting fact is that the World Wide Web (WWW) was invented by a British scientist while working at CERN. More information regarding this can be seen in the following Fig. 7 and Fig. 8.
Fig. 7: Tim Berners-Lee at CERN and a graph showing the growth of internet users since the discovery.
Fig. 8: WWW (World Wide Web)
The Large Hadron Collider (LHC), designed and developed at CERN, is the most powerful particle accelerator in the world. It is basically a ring made of superconducting magnets. These magnets are supported by accelerating structures to increase the energy of the particles along their way. The beams inside the LHC are made to collide at four different locations, giving rise to the position of four detectors – ATLAS, CMS, ALICE and LHCb.
These particles are then made to collide at a speed close to that of light, giving us an insight into the fundamental laws of nature and understanding particle behavior at an even more microscopic level than was ever imaginable.
Let’s now discuss each of the LHC’s detectors briefly.
One of the four major experiments of the Large Hadron Collider, ATLAS, is deeply involved with discovering some of the most exciting details of particle physics. It explores the Higgs-boson, or the "God particle", and digs deeper into dark matter, trying to find out its particulate nature. Fig. 9, taken from the exhibit itself, provides a better understanding of the above mentioned.
Fig. 9: ATLAS.
The detector is a multi-layered instrument designed in such a way that it can detect some of the smallest and most energetic particles that come along its way. Over a billion particle interactions occur in its detector just every second. But only one in a million collisions provide interesting results that are further examined.
The Compact Muon Solenoid, or the CMS, is a general-purpose detector that uses a huge solenoid magnet to bend the paths of particles during their collisions at the LHC. Its scientific goals are like those of the ATLAS experiment, but differences lie in the magnet systems used in the detector. A good description of the CMS detector has been provided below in Fig. 10.
Fig. 10: CMS.
ALICE (A Large Ion Collider Experiment) detects quark-gluon plasma. All matter is made up of atoms. Each atom consists of a nucleus which has protons and neutrons, surrounded by a cloud of electrons. (Hydrogen is an exception, as its nucleus has no neutrons). Protons and neutrons are further made of quarks. Quarks are held together by gluons. Quarks and gluons have not been found to exist in isolation yet, and are permanently bound to each other. This condition is known as confinement.
At extremely high temperatures (created artificially) in the LHC for particle collisions, protons and neutrons “melt”, resulting in a breakage in the quark-gluon bond. This is quark-gluon plasma, and comes under a branch of particle physics called quantum chromodynamics (QCD).
The Large Hadron Collider Beauty Experiment tries to explain why our Universe consists of matter, but not antimatter. It does so by studying a type of particle called the beauty quark, or b quark. The matter-antimatter question has been simply explained in Fig. 11.
Fig. 11: LHCb
Thirty Meter Telescope
The Thirty Meter Telescope, or TMT, is a highly advanced and new telescope that will allow us to dig deeper into space and allow for better observations. Its prime mirror has a diameter of 30m and it will be thrice as wide, with 9 times the area of the currently largest visible light telescope in the whole world.
Fig. 12 shows the various components of the TMT, as taken from the exhibit.
Fig. 12: Thirty Meter Telescope.
This will result in the TMT images being more than 12 times sharper than those from the Hubble Space Telescope.
The TMT’s unique capabilities and high technologies will give astronomers the chance to pursue deep research on exoplanets to find out whether life exists beyond the Earth. Its high resolution will also allow the detection of black holes that are a part of different galaxies. It will also help in providing useful information about the beginning of the Universe in terms of dark matter.
The TMT International Observatory LLC (TIO) is responsible for the design and development of the TMT. TIO is an international partnership between a few countries, including India.
The concept and working of the TMT were explained to us in a great manner by a scientist working at the prestigious Bhabha Atomic Research Center (BARC).
Along with this, he also introduced us to the Major Atmospheric Cerenkov Experiment Telescope (MACE). In altitude, it is the highest Cerenkov Telescope in the world and was built by Electronics Corporation of India, Hyderabad for BARC. This telescope is located at Hanle in Ladakh, India and is also the second largest gamma ray telescope in the world. Fig. 13 gives the specifications of this telescope.
The MACE Telescope will enhance our understanding in astrophysics, fundamental physics and particle acceleration mechanisms.
Fig. 13: MACE Telescope.
India-based Neutrino Observatory (INO)
The India-Based Neutrino Observatory (INO) (Fig. 14) is a project aimed at developing a world class underground laboratory for non-accelerator based high energy and nuclear physics research in India. The project is jointly funded by the Department of Atomic Energy and the Department of Science and Technology, Government of India.
Fig. 14: India-based Neutrino Obervatory.
The main goal of the INO is to study neutrinos. Neutrinos are fundamental particles and belong to the lepton family. (Leptons are elementary particles and there are six different ones according to the Standard Theory). Also, according to the Standard Theory, neutrinos are massless. However, recent experiments and research have shown that these electromagnetically neutral particles have a small finite mass, which remains unknown. Determining the masses and studying more about the properties is a challenging task which has taken particle physics to greater heights.
There were other smaller exhibits which I would have loved to visit but couldn’t due to time restraints.
Overall, the entire experience was highly enriching and inspiring. It was a great opportunity as a student, to learn so much about the field I am interested in, by interacting with people who actually work on such projects. The highlight of this visit for me was learning about India’s collaborations with LIGO and knowing how much we have advanced in this field.