CERN’s at it again, but it’s not particle physics. Einstein’s also at it again, but this time, it isn’t the famed grizzly haired scientist. A group of European scientists working with CERN will soon propose a design for a telescope the Einstein Observatory - which will be much better than any other known telescope of its kind. The catch: This one will detect gravitational waves rather than optical radiation or radio waves.
What is the Einstein Observatory
The Einstein Observatory (EO) is a ‘third-generation’ gravitational wave detector and it is designed to be at least a 100 times more sensitive that its existing predecessors. The principle of detection is simple and classic. The arms of the Observatory, each several kilometers long and each being a laser beam will shrink or expand ever so slightly if a gravitational wave passes. This will cause a change in the interference pattern in a central photo-detector. Let’s look at this in more detail.
Einstein’s theory of General Relativity predicts that gravitational energy, stored in gravitational fields, should be released as waves, just like energy in electromagnetic fields is released by electromagnetic waves (which we call light). The problem is that, unlike light, the energy of a gravitational wave is so small that if a typical one passes by earth right now, the earth will shrink and then expand by the breadth of a proton which is much much smaller than even an atom. Detecting such small perturbations is a huge challenge that has so far been unconquered. Relativity predicts that gravitational waves of comparatively large magnitude are emitted by violent cosmic events, like merging of black holes, or fusing of neutron stars, or even supernova explosions. These will be the typical gravitational waves scientists hope to detect with EO. The success of Einstein’s theory has been such that no one doubts the existence of gravitational waves, even though one hasn’t been detected inspite of dedicated search.
What EO intends to do is this: there is a particular way two beams of light interfere with each other.
They form a well-known pattern called an interference pattern (you might see these patterns when water waves interfere). A slight shift in the path a beam of light travels will disturb these patterns. The process is extremely sensitive – and if the beams travel a long distance before interfering, the sensitivity increases. (For science buffs: This is the same principle first used by Michelson in his famous experiment for measuring the speed of light and later, the most famous ‘failed’ experiment in history. This failed experiment, known simply as Michelson-Morley experiment, aimed to detect a change in the speed of light in different directions so as to confirm the aether hypothesis. None was detected. Einstein would later build his Special Theory of Relativity around this result.)
More on the EO
The EO will be housed 100 to 200 meters below ground, in order to minimize the seismic activity of the ground and its effect on the telescope. The EO will be extremely sensitive in the range 1 Hz to 10 kHz, which is the frequency band for the gravitational waves. The Einstein Observatory will lead a scientific revolution, is what Michele Punturo, scientific coordinator of the design, says. The data from the EO will be corroborated and complemented by data from various gamma-ray and X-ray telescopes.
The EO is actually two interferometers one to detect gravitational wave signals from 2-40 Hz and the other to detect till 10 kHz. This is required, since detecting at low frequencies is a very difficult job and needs dedicated instruments tuned for doing only that.
EO will hope to improve upon existing gravitational wave telescopes like LIGO, Virgo and TAMA (all first generation), and even Advanced LIGO and Advanced Virgo (second generation). The design will be presented at European Gravitational Observatory site in Pisa, Italy.
It is of utmost importance to the progress of cosmology that the telescope, like the illustrious scientist it is named after, becomes as successful as his theories.