19 March,2014 09:00 AM IST | | Dr Nimesh Patel and Dr Tarun Souradeep
With the inflation theory receiving observational proof, we stand at the cusp of a hugely exciting breakthrough in cosmology
On March 17, 2014, humanity came one step closer to understanding the universe, how it began and ultimately, who we are and where did we come from. And it was all done by a group of young scientists that included several students.
Courtesy: Wikimedia Commons
The first observational evidence was reported for the rapid expansion of the Universe that occurred within a fraction of a second after Big Bang. This discovery also confirms the existence of gravitational waves in these very early moments during the birth of our Universe.
At the Harvard University conference, it is goosebumps time at the evidence provided by the BICEP2 team
The discovery was made using a new telescope at the South Pole, called the Background Imaging of Cosmic Extragalactic Polarization (BICEP2) and the results were presented by the team leader Dr. John Kovac. This announcement comes just weeks after a public event that was held at our institute to celebrate 50 years of the discovery of the Cosmic Microwave Background (CMB).
This discovery of the 3K radiation, a cooled leftover radiation from the creation of our Universe about 13.8 billion years ago, was made in 1964 by Arno Penzias and Robert Wilson, for which they were awarded the Nobel prize in 1978.
Pasadena, California, USA: This image released by NASA/JPL-Caltech on March 17, 2014 shows the BICEP2 telescope at the South Pole that uses novel technology developed at NASA's Jet Propulsion Laboratory in Pasadena, California. Pic/AFP
Detailed all-sky maps of the CMB were subsequently made using the satellite observatories, first the Cosmic Background Explorer (COBE, 1989) satellite and later the Wilkinson Microwave Anisotropy Probe (WMAP, 2001), which show that the CMB is not uniform, but consists of brighter and dimmer regions differing by about one part in a hundred thousand.
These fluctuations are the seeds from which stars, galaxies, and clusters of galaxies form as the universe expands. The pattern of these fluctuations reveals the universe when it was about 380,000 years old after the Big Bang.
In addition, the CMB radiation is polarized (that is, the light waves have a preferred plane of oscillation, just like the light filtered by polarized sun glasses, or light reflected from a plane surface such as a road or a lake).
Both the amounts of these fluctuations in the CMB as a function of angular scale and the pattern of polarization on the sky, are directly observable quantities that can be used to test various theoretical cosmological models of the very early universe, and it is quite remarkable that it is now possible to test these models observationally, up to just 1 second after the big bang.
And the results presented on March 17, probe the universe even as early as a trillion, trillion, trillionth of a second after the Big Bang! The time interval of 0.000000000000000000000000000000000001 seconds after Big Bang is when the universe expanded at an exponential rate, to a size of about a marble, according to the "Inflation" theory, proposed by Prof.
Alan Guth (MIT) and Andrei Linde (Stanford) in the 1980s. Inflation, using Dr. Guth's words, is the "bang" of the Big Bang. Inflation is what explains the expansion. (Inflation is not to be confused with the recent discovery of the "acceleration" in expansion, which is supposed to have started much later, about 5 to 7 billion years after the Big Bang).
Although the theory of inflation was supported by previous CMB measurements with the WMAP satellite, the latest results today by the BICEP2 team provide a key piece of observational evidence in the imprint of the predicted pattern of polarization.
The "swirly" pattern of polarization is predicted by perturbations caused by gravitational waves during inflation, not just disturbances in density (which would cause polarization in linear/radial rather than curling pattern). It is this characteristic pattern of polarization, the so-called B-mode polarization, which is considered to be the Holy Grail in the field of CMB research. The BICEP2 group appears to have nailed it.
Every great scientific result needs stringent verification, which will necessarily follow, and in the next few months, similar results are expected from other instruments, including the Planck satellite. I am not involved in this groundbreaking research, but I was really excited to have been present when this announcement was made. This discovery is extremely significant since the question addressed is so fundamental: How did our universe begin?
Dr Nimesh Patel, Mumbai-born astrophysicist, works at the Harvard Smithsonian Center for Astrophysics in the Radio Astronomy division. He also teaches an undergraduate astronomy course at Harvard University.
What is the theory?
The Big Bang theory suggests that the universe got very big very fast; transforming itself in a fraction of an instant from something almost infinitely small to something extremely vast and gigantic, a cosmos so huge that no one will ever be able to see it all.
Prof John Kovac on the dais
On Monday, this theory received a major boost from an experiment at the South Pole called BICEP2. This telescope stationed by researchers found evidence of the oldest light in the universe.
A team of astronomers led by John Covac of the Harvard-Smithsonian Center for Astrophysics announced that it had detected ripples from gravitational waves created in a violent inflationary event at the dawn of time.
These findings show that the universe underwent a burst of inflation that was faster than the speed of light in the first instant of its existence, throwing off a storm of exotic gravitational waves in the process.
Einstein's predictions are coming true
The search for signatures of gravitational waves from the very early moments of the universe has been the primary, high-value target (a sort of âHoly Grail') for Cosmic Microwave Background experiments in the past few years. These are very exciting results with great impact for science and for the very human quest to understand our origins.
An artist's impression of the WMAP satellite which is helping us understand the Big Bang (Courtesy: NASA)
It is a first direct observation of gravitational waves, a prediction of Albert Einstein's theory of gravitation proposed a century ago. It lends credence to certain aspects of the understanding in reconciling the two major revolutions in 20th-century physics - quantum mechanics and Einstein's gravity.
The concept of inflation proposed about in 1980 by Prof Alan Guth is a widely held idea in contemporary cosmology. It provided a convenient mathematical framework for understanding the origin and evolution of universe and structures such galaxies within it.
An idea of such central importance begs for observational justification. Although there are many ways of realising the concept of Inflation, there are a few key generic predictions. The generation of gravitational waves during inflation, poetically described as "tremors of Big Bang" is the last one in the list to be experimentally confirmed.
However, it is important bear in mind that these observations do not dent the importance the expected direct measurements of gravitational waves using man-made apparatus such as LIGO (Laser Interferometer Gravitational-Wave Observatory).
These measure gravitational waves from astrophysical objects at audio range of frequencies. In fact, there is a mega-science proposal, LIGO-India, under active consideration in India at this time.
The results announced on March 17 in the US are from a respected and capable experimental group. However, as in any such result of great impact, these measurements need to face up to further scrutiny and confirmation from follow-up measurements.
Fortunately, it should be possible for a number of other experiments to verify these results in the near future. The Planck satellite would be announcing its measurements of CMB polarisation later in the year which is expected to be able to address these results independently.
A group of Indian scientists from the Pune-based Inter-University Centre for Astronomy and Astrophysics (IUCAA) are members of the international Planck collaboration.
Prof Tarun Souradeep is an astrophysicist at the Inter-University Centre for Astronomy and Astrophysics in Pune. He is the leader of the Indian team working for the Planck international collaboration to detect gravitational waves
