Einstein's Theory of General Relativity Archives

October 13, 2024October 13, 2024 by Matt Williams

New Research Could Help Resolve the “Three-Body Problem”

Zine Tseng as Chinese radio astronomer, sitting at control panel for antenna — Zine Tseng plays a Chinese radio astronomer in "3 Body Problem." (Credit: Ed Miller / Netflix © 2024)

Perhaps you’ve heard of the popular Netflix show and the science fiction novel on which it is based, The Three-Body Problem, by Chinese science fiction author Liu Cixin. The story’s premise is a star system where three stars orbit each other, which leads to periodic destruction on a planet orbiting one of them. As Isaac Newton described in his Philosophiæ Naturalis Principia Mathematica, the interaction of two massive bodies is easy to predict and calculate. However, the interaction of three bodies leads is where things become unpredictable (even chaotic) over time.

This problem has fascinated scientists ever since and remains one of the most famous unsolved mysteries in mathematics and theoretical physics. The theory states that the interaction of three gravitationally bound objects will evolve chaotically and in a way that is completely detached from their initial positions and velocities. However, in a recent study, an international team led by a researcher from the Niels Bohr Institute ran millions of simulations that showed “isles of regularity in a sea of chaos.” These results indicate that there could be a solution, or at least some predictability, to the Three-Body Problem.

May 8, 2023May 8, 2023 by Matt Williams

LISA Will Be a Remarkable Gravitational-Wave Observatory. But There’s a Way to Make it 100 Times More Powerful

Artist's impression of the Laser Interferometer Space Antenna (LISA). Credit: ESA

The first-time detection of Gravitational Waves (GW) by researchers at the Laser Interferometer Gravitational-wave Observatory (LIGO) in 2015 triggered a revolution in astronomy. This phenomenon consists of ripples in spacetime caused by the merger of massive objects and was predicted a century prior by Einstein’s Theory of General Relativity. In the coming years, this burgeoning field will advance considerably thanks to the introduction of next-generation observatories, like the Laser Interferometer Space Antenna (LISA).

With greater sensitivity, astronomers will be able to trace GW events back to their source and use them to probe the interiors of exotic objects and the laws of physics. As part of their Voyage 2050 planning cycle, the European Space Agency (ESA) is considering mission themes that could be ready by 2050 – including GW astronomy. In a recent paper, researchers from the ESA’s Mission Analysis Section and the University of Glasgow presented a new concept that would build on LISA – known as LISAmax. As they report, this observatory could potentially improve GW sensitivity by two orders of magnitude.

May 3, 2023May 5, 2023 by Matt Williams

Gravitational Lensing is Helping to Nail Down Dark Matter

Using the gravitational lensing technique, a team was able to examine how light from distant quasar was affected by intervening small clumps of dark matter. Credit: NASA/ESA/D. Player (STScI)

According to the most widely-accepted cosmological model, the majority of the mass in our Universe (roughly 85%) consists of “Dark Matter.” This elusive, invisible mass is theorized to interact with “normal” (or “visible”) matter through gravity alone and not electromagnetic fields, neither absorbing nor emitting light (hence the name “dark”). The search for this matter is ongoing, with candidate particles including Weakly-Interacting Massive Particles (WIMPs) or ultralight bosons (axions), which are at opposite extremes of the mass scale and behave very differently (in theory).

This matter’s existence is essential for our predominant theories of gravity (General Relativity) and particle physics (The Standard Model) to make sense. Otherwise, we may need to radically rethink our theories on how gravity behaves on the largest of scales (aka. Modified Gravity). However, according to new research led by the University of Hong Kong (HKU), the study of “Einstein Rings” could bring us a step closer to understanding Dark Matter. According to their paper, the way Dark Matter alters the curvature of spacetime leaves signatures that suggest it could be made up of axions!

December 14, 2021December 14, 2021 by Matt Williams

Twin Stars Prove Einstein at Least 99.99% Right

Artistic impression of the Double Pulsar system, where two active pulsars orbit each other in just 147 min. The orbital motion of these extremely dense neutrons star causes a number of relativistic effects, including the creation of ripples in spacetime known as gravitational waves. The gravitational waves carry away energy from the systems which shrinks by about 7mm per days as a result. The corresponding measurement agrees with the prediction of general relativity within 0.013%. The picture at high resolution and two alternative versions (1b, 1c) are accessible in the left column. [less] © Michael Kramer/MPIfR

More than a hundred years have passed since Einstein formalized his theory of General Relativity (GR), the geometric theory of gravitation that revolutionized our understanding of the Universe. And yet, astronomers are still subjecting it to rigorous tests, hoping to find deviations from this established theory. The reason is simple: any indication of physics beyond GR would open new windows onto the Universe and help resolve some of the deepest mysteries about the cosmos.

One of the most rigorous tests ever was recently conducted by an international team of astronomers led by Michael Kramer of the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany. Using seven radio telescopes from across the world, Kramer and his colleagues observed a unique pair of pulsars for 16 years. In the process, they observed effects predicted by GR for the first time, and with an accuracy of at least 99.99%!

August 14, 2021August 14, 2021 by Brian Koberlein

Matter From Light. Physicists Create Matter and Antimatter by Colliding Just Photons.

An artistic view of light becoming matter. Credit: Gerd Altmann, via Pixabay

In 1905 Albert Einstein wrote four groundbreaking papers on quantum theory and relativity. It became known as Einstein’s annus mirabilis or wonderous year. One was on brownian motion, one earned him the Nobel prize in 1921, and one outlined the foundations of special relativity. But it’s Einstein’s last 1905 paper that is the most unexpected.

April 12, 2021April 12, 2021 by Matt Williams

Gaia Finds 12 Examples of Einstein Crosses; Galaxies Being Gravitationally Lensed so we see Them Repeated 4 Times

Credit and : R. Hurt (IPAC/Caltech)/The GraL Collaboration

In 1915, Einstein put the finishing touches on his Theory of General Relativity (GR), a revolutionary new hypothesis that described gravity as a geometric property of space and time. This theory remains the accepted description of gravitation in modern physics and predicts that massive objects (like galaxies and galaxy clusters) bend the very fabric of spacetime.

As result, massive objects (like galaxies and galaxy clusters) can act as a lens that will deflect and magnify light coming from more distant objects. This effect is known as “gravitational lensing,” and can result in all kinds of visual phenomena – not the least of which is known as an “Einstein Cross.” Using data from the ESA’s Gaia Observatory, a team of researchers announced the discovery of 12 new Einstein Crosses.

September 9, 2020September 10, 2020 by Matt Williams

Behold! The Black Hole Collision Calculator!

This image shows two massive black holes in the OJ 287 galaxy. The smaller black hole orbits the larger one, which is also surrounded by a disk of gas. When the smaller black hole crashes through the disk, it produces a flare brighter than 1 trillion stars. Credit: NASA/JPL-Caltech

Black holes have been the subject of intense interest ever since scientists began speculating about their existence. Originally proposed in the early 20th century as a consequence of Einstein’s Theory of General Relativity, black holes became a mainstream subject a few decades later. By 1971, the first physical evidence of black holes was found and by 2016, the existence of gravitational waves was confirmed for the first time.

This discovery touched off a new era in astrophysics, letting people know collision between massive objects (black holes and/or neutron stars) creates ripples in spacetime that can be detected light-years away. To give people a sense of how profound these events are, Álvaro Díez created the Black Hole Collision Calculator (BHCC) – a tool that lets you see what the outcome of a collision between a black hole and any astronomical object would be!

July 24, 2020July 24, 2020 by Matt Williams

The Moon is an Ideal Spot for a Gravitational Wave Observatory

High-resolution view of the lunar surface (JAXA/SELENE)

In the coming years, multiple space agencies will be sending missions (including astronauts) to the Moon’s southern polar region to conduct vital research. In addition to scouting resources in the area (in preparation for the construction of a lunar base) these missions will also investigate the possibility of conducting various scientific investigations on the far side of the Moon.

However, two prominent scientists (Dr. Karan Jani and Prof. Abraham Loeb) recently published a paper where they argue that another kind of astronomy could be conducted on the far side of the Moon – Gravitational Wave astronomy! As part of NASA’s Project Artemis, they explain how a Gravitational-wave Lunar Observatory for Cosmology (GLOC) would be ideal for exploring GW in the richest and most challenging frequencies.

April 25, 2020April 25, 2020 by Matt Williams

A Star is Orbiting the Milky Way’s Black Hole and Moving Exactly How Einstein Predicted it Should

Observations made with ESO’s Very Large Telescope (VLT) have revealed for the first time that a star orbiting the supermassive black hole at the centre of the Milky Way moves just as predicted by Einstein’s theory of general relativity. Its orbit is shaped like a rosette and not like an ellipse as predicted by Newton's theory of gravity. This effect, known as Schwarzschild precession, had never before been measured for a star around a supermassive black hole. This artist’s impression illustrates the precession of the star’s orbit, with the effect exaggerated for easier visualisation.

At the center of our galaxy, roughly 26,000 light-years from Earth, is the Supermassive Black Hole (SMBH) known as Sagittarius A*. The powerful gravity of this object and the dense cluster of stars around it provide astronomers with a unique environment for testing physics under the most extreme conditions. In particular, it offers them a chance to test Einstein’s Theory of General Relativity (GR).

For example, in the past thirty years, astronomers have been observing a star in the vicinity of Sagittarius A* (S2) to see if its orbit conforms to what is predicted by General Relativity. Recent observations made with the ESO’s Very Large Telescope (VLT) have completed an observation campaign that confirmed that the star’s orbit is rosette-shaped, once again proving that Einstein theory was right on the money!

January 11, 2020January 11, 2020 by Matt Williams

Hubble Finds Teeny Tiny Clumps of Dark Matter

To put it simply, Dark Matter is not only believed to make up the bulk of the Universe’s mass but also acts as the scaffolding on which galaxies are built. But to find evidence of this mysterious, invisible mass, scientists are forced to rely on indirect methods similar to the ones used to study black holes. Essentially, they measure how the presence of Dark Matter affects stars and galaxies in its vicinity.

To date, astronomers have managed to find evidence of dark matter clumps around medium and large galaxies. Using data from the Hubble Space Telescope and a new observing technique, a team of astronomers from UCLA and NASA JPL found that dark matter can form much smaller clumps than previously thought. These findings were presented this week at the 235th meeting of the American Astronomical Society (AAS).