TechPulsar discovery confirms Einstein's theory, ushering new era in cosmic exploration

Pulsar discovery confirms Einstein's theory, ushering new era in cosmic exploration

Albert Einstein predicted phenomena that were proven to exist only 100 years later.
Albert Einstein predicted phenomena that were proven to exist only 100 years later.
Images source: © Public domain

7:07 PM EST, January 16, 2024

A pulsar operates akin to a cosmic lighthouse - rotating quickly around its own axis, while emitting a beam of electromagnetic radiation. When observed from Earth, it appears the celestial object periodically emits an electromagnetic "pulse" at consistent intervals.

The subsequent "flashes" appear cyclically and consistently enough that a pulsar becomes a useful tool for precise time measurement-- its accuracy rivals that of an atomic clock. This meticulous observation of its behavior was Hulse and Taylor’s Nobel-worthy endeavor.

The breakthrough commenced with an observation of PSR B1913+16 - a system comprising a pulsar and a neutron star. Although the name might appear unappealing, its significance for our understanding of the Universe is inestimable.

Pulsar validates Einstein's theory

The crux of Hulse and Taylor's scientific discovery was their measurements, which indicated that the celestial bodies of this system are orbiting faster and faster – with an acceleration of 0.0000765 seconds per year and the system's orbit tightening by roughly 11.5 feet annually.

While this might appear insignificant owing to the vast distances inherent in space, it underlines a crucial fact: Einstein was right. The tightening orbit implies that the system is losing energy for some reason. But what's causing this loss?

The answer was hinted at by the general theory of relativity: energy "seeps" out of the system in the form of gravitational waves, cast as ripples in space-time.

Even though these waves were not directly observed in the '70s, Hulse and Taylor's findings insinuated their existence and subsequently, their measurable impact on our reality, as predicted by Einstein.

The significant "L"

There lies a considerable gap of scientific skepticism between "should exist" and "does exist". In this matter, the gap was 42 years long. That's how much time passed between Hulse and Taylor’s Nobel Prize and the announcement of tangible evidence of gravitational waves, which was later awarded a Nobel Prize as well.

It's important to note that the official announcement doesn't always align with the moment of discovery - the results announced in early February 2016 pertained to research conducted six months prior.

The instrument used for this research was the American gravitational waves detector, LIGO - twin installations roughly 1865 miles apart, one in Washington and the other in Louisiana. They comprise long (the longer, the better), empty tubes laid out in the shape of an "L".

The tube shields a near vacuum through which a laser light beam is projected from the juncture where both tubes meet. The longer the light travels, the higher the chance of observing deviations resulting from the effect of gravitational waves.

LIGO gravitational wave detector
LIGO gravitational wave detector© LIGO Lab

Although both arms of the detector are precisely the same length, a gravitational wave causes the light to traverse a marginally shorter distance in one of them. "Marginally" is billions of times less than the diameter of an atom nucleus, but large enough to determine that our reality has been skewed: the light took a slightly shorter path because the gravitational wave bent space-time.

How long should such a ruler be to indicate the passage of gravitational waves? To enlarge the scale of detected distortions, mirrors are placed in the detectors to reflect the laser dozens or hundreds of times.

Thanks to this, for instance, the LIGO detector, whose arms are 2.5 miles long, enables studying the behavior of the light beam over several hundreds of miles. To reduce local disturbance interference, the gathered data is compared with that provided by the European Virgo detector: all detectors should independently register anomalies when gravitational waves pass.

However, there's a three-sun mass discrepancy in the total calculation. What became of them? They were dispelled in the form of gravitational waves during the astral collision. These waves hurtled across the cosmos, reaching Earth in 2015, where they interacted with the light transmitted through the detector arms.

Interestingly, Einstein also hypothesized that mass not only warps ("depresses") space-time but also sets it spinning (Lense-Thirring effect), which was corroborated in 2020 in a study of the pulsar PSR J1141-6545.

A brisk voyage to cosmic boundaries

Research on gravitational waves will be easier in the future as we might not need to construct terrestrial detectors, but can put cosmic objects to use. An example is a plan to use mirrors placed on the moon during the Apollo 11, 14, and 15 missions for studies. Laser-irradiated, they would permit measuring of distortions occurring not over a few kilometers, like terrestrial detectors, but over the 238,900-mile distance between Earth and the moon. But why?

Gravitational waves carry invaluable information. Even though detecting them may feel like, in Professor David Blair's words - eavesdropping on vibrations a door makes when knocked on from 6,200 miles away, they relay information on what occurred in the Universe. They don't provide a visual image, but behave more like an echo of distant events.

Theoretically, their study brings us closer to comprehending the process of space-time warping. It might seem abstract for now, but perhaps in the future, Earthlings will travel vast distances through this method, bypassing the speed of light limit and time dilation issues. Theoretical groundwork for such journeys, like the Alcubierre drive (compressing space-time ahead and expanding it behind the ship), already exists.

Practically, studying gravitational waves allows us to observe what occurred a long-distance away and in the distant past. Combined with other vast cosmological studies, it brings us closer to understanding the phenomena and processes that shaped our Universe.

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