Last year, there was much excitement as scientists at the BICEP2 telescope at the South Pole claimed to have gathered evidence of gravitational waves that were released shortly after the Big Bang.
However, it was later shown that intergalactic dust had led them astray in their observations, and they had not detected gravitational waves at all.
This leaves the field open for experimental groups to search for first direct evidence of gravitational waves. The experiments are very challenging, given the fact that these waves are very faint and extremely difficult to detect; many groups are involved in this endeavour. One of these is the Laser Interferometer Gravitational-wave Observatory (LIGO), designed and operated by Caltech and MIT.
This detector recently underwent upgradation which would make it ten times more sensitive, which, in turn, would provide a 1000-fold increase in the number of astrophysical candidates for gravitational wave signals. This upgraded detector was officially dedicated in a ceremony held on May 19.
“We’ve spent the past seven years putting together the most sensitive gravitational-wave detector ever built… we are looking forward to our first science run with Advanced LIGO beginning later in 2015. This is a very exciting time for the field,” Caltech’s David H. Reitze, executive director of the LIGO Project, noted in a press release.
As early as 1916, Einstein predicted gravitational waves as a consequence of his general theory of relativity. Gravitational waves are ripples in the fabric of space-time produced by violent events such as the collision of two black holes or by cores of supernova explosions. They are produced by accelerating masses, just the same as accelerating charged particles produce radio waves (e.g. electrons in antennas). Among other things, studying gravitational waves can tell us more about the nature of gravity.
In fact, the waves have not been directly detected so far, but indirect evidence that they exist comes from 1974 discovery of the Hulse-Taylor binary pulsar whose period of orbit decreases in a manner exactly predicted by general theory of relativity. This system is believed to emit gravitational waves, in accordance with what Einstein had predicted would happen to masses moving relatively to each other. Russell Hulse and Joseph Taylor were awarded the Nobel Prize for this discovery in 1993.
The advanced LIGO will also be used to search for gravitational cosmic background.
Gravitational wave detectors receive signals from all directions. However, to locate the sources of the waves, a network of detectors is needed. There is a proposal (LIGO-India) to establish one such detector in India.
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