Why do scientists shoot a laser at the Moon and what does gravitational waves have to do with it?

(ORDO NEWS) — A group of European researchers have suggested that the Moon‘s orbit could be used as a giant detector of gravitational waves – pulsations in the very fabric of space-time. These waves are much smaller than what existing detectors can pick up and could have come from the early universe.

Cosmic events involving huge masses and objects, such as collisions between black holes, can release so much energy that they physically distort the space-time continuum, causing ripples known as gravitational waves.

Although this phenomenon was first predicted by Albert Einstein over a century ago, gravitational waves were not directly detected until 2015.

To catch gravitational waves, instruments such as LIGO and the Virgo laser system must travel down 4 km tunnels and lie low.

The reason is that after reducing other environmental influences, any tiny change in the field of the laser beam may indicate that it has been overwhelmed by a gravitational wave, literally distorting reality.

This distortion may be only one thousandth of the width of a proton, but such sensitive instruments are quite capable of detecting them.

How to catch a gravitational wave

Dozens of detections have been made over the years, but current technology can only pick up signals within certain frequencies.

In a new study , a team from UAB and IFAE in Spain and University College London have come up with a new way to detect gravitational waves at much lower frequencies using the Moon’s orbit around the Earth.

Why do scientists shoot a laser at the Moon and what does gravitational waves have to do with it 2

The Apollo astronauts left mirrors on the Moon’s surface, which allows observatories on Earth to continuously aim lasers at them and measure how reflective they are.

This gives scientists the ability to track the distance of the Moon from Earth to within 1 cm. In some ways, this is a much larger version of existing gravitational wave detectors, but where LIGO lasers travel only 4 km, the average distance to the Moon is 384,400 km.

The accuracy of our measurements to the Moon, the additional distance, and the fact that the Moon takes 28 days to orbit the Earth make this method especially sensitive to detecting gravitational waves in the microhertz range.

These frequencies are beyond the capabilities of existing detectors on Earth, but are of particular interest to scientists.

Microhertz gravitational waves are thought to have come from the very early universe as it undergoes transitions between high energy phases. Detecting and deciphering these waves can reveal a huge amount of new information about a difficult period in the history of the universe to study.

This is not the first time the Moon has been considered for a role in detecting gravitational waves. Last year, another team suggested that the lunar surface could be an ideal location for a future object due to its isolation from background noise.

However, the main advantage of the new proposal is that it does not require the construction of a new facility at all – existing technologies can simply be repurposed.


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