Explained: The Idea Of An Observatory On The Moon To Detect Gravitational Waves – Swarajya

Cosmic events of unimaginable magnitude are unfolding everywhere in the universe.

The news of these developments come to us, here on Earth, in a variety of forms.

For the scientific community, it is a matter of being at the right place at the right time and hopefully with the right equipment to receive this news of developments happening in distant reaches.

Two astrophysicists have proposed an idea that seeks to assemble this trio of right factors in order to detect objects and events hidden from plain view, in many cases even electromagnetic view.

Scientists Dr Karan Jani and Professor Abraham Loeb have suggested that a gravitational-wave observatory be put on the Moon to improve our ability to look deeper into space.

The Moon, they say, would make an excellent base for detection of gravitational waves.

The idea of gravitational waves originated in Albert Einstein's theory of general relativity.

It remained a prediction for a century (indirect evidence in 1974) until in 2015, it was confirmed with the Laser Interferometer Gravitational-wave Observatory (LIGO) gravitational waves were detected from 1.3 billion years ago after two spiralling black holes had crashed into each other.

Since then, gravitational-wave detectors in the United States and Europe have been chasing gravitational signals from remote locations underground.

Together, they have detected scores, some 50 of them, in the last five years.

Future projects like the Einstein Telescope and Cosmic Explorer promise to help refine our abilities to probe further.

However, gravitational-wave detectors based on Earth, and even space, may not be enough in our quest for some of the more mysterious objects in space.

They have limitations that could be reduced or done away with if the detector was instead put to work on the Moon.

Gravitational-wave observatory on the Moon

The Laser Interferometer Gravity-wave Observatory (LIGO) and VIRGO experiments have been doing a fine job at detections in the 10-1000 Hz spectrum.

Future labs are set to shine a light on lower frequencies around 5 Hz in the case of Earth-based observatories and down to milli-Hz in the case of the space-based Laser Interferometer Space Antenna (LISA).

However, theres much to gain from tuning the frequency down further, to a spectrum of deci-Hz to 1 Hz.

The Moon is apt for this range.

This frequency range tends to be too low for Earth-based detectors and too high for space missions, write the authors in their paper.

The universe offers a rich set of astrophysical sources in this regime.

Detection of gravitational waves in this low-frequency domain could help one of the authors of the paper, Dr Jani, verify the existence of a cosmic object of his passion.

I am very interested in intermediate-mass black holes. They are smaller than the monster black holes found at the centres of galaxies, and are a mysterious class with no confirmed existence. But with gravitational waves, we can detect any black holes, says Dr Jani.

The low 0.1-5 Hz frequency range opens the doors to detecting these intermediate-mass black holes.

In addition, its possible to explore 30-80 per cent of the observable universe with the proposed Gravitational-wave Lunar Observatory for Cosmology (GLOC), vastly expanding the search area.

The Moon is apt for detection

The Moon lends itself better to detection of gravitational radiation in comparison to Earth.

For one, it is much quieter there than where we are.

Thanks to that, the lunar detector will not have to deal with geological rumblings on the Moons surface, which is especially important in the case of low-frequency detection.

For less than 10 Hz, we start to have seismic noise on Earth that couples with the detector. The Moon is at least 1,000 times quieter than Earth, says Dr Jani.

On the Moon, the size of the observatory can be scaled up.

Currently, the LIGO detectors have two arms at a length of 4 km each.

The arms are made up of over a metre-wide steel vacuum tubes arranged in an "L" shape and protected from the environment by concrete.

Dr Jani and Professor Loeb propose expanding the arms out 10 times to make the arm length 40 km on the Moon.

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Explained: The Idea Of An Observatory On The Moon To Detect Gravitational Waves - Swarajya

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