Cosmology

Gravitational Waves
Here is the simulation of the Gravitational Waves

Introduction

On February 11, 2016 scientists announced the first direct detection of gravitational waves whose existence was first proposed by Albert Einstein, in 1916. Finally having direct evidence for a phenomenon that was first predicted 100 years ago, using an instrument that was proposed 40 years ago.

Detecting the Gravitational Waves

The waves came from two black holes circling each other, closer and closer, until they finally collided. The recently upgraded Laser Interferometer Gravitational Wave Observatory (LIGO) captured the signal on Sept. 14, 2015. Researchers said the collision occurred 1.3 billion years ago between black holes that were about 29 and 36 times more massive than the sun, respectively. During the crash, about three times the mass of the sun was converted into gravitational waves in less than a second, generating a peak power output of about 50 times that of the entire visible universe

Theory that Leads to the Formulation of the Gravitational Waves

Einstein’s theory of general relativity can be summarized in two statements: Matter tells space and time how to curve and curved space and time tell matter how to move. Einstein realized the consequence of distorting space and time which is, general relativity allows for gravitational waves, which are rhythmic distortions which propagate through space at the speed of light.

General relativity states that space and time are not separate things but rather are linked together in a single fabric: space-time. Massive objects stretch and curve this fabric. These dips cause objects such as planets, and even light, to take a curved path around those more massive bodies

Gravitational waves affect this fabric as well, causing ripple like distortions.

Nature of the Gravitational Waves

Gravitational waves are ripples in the fabric of space-time which are produced by the acceleration or deceleration of massive objects in space.

Gravitational waves produce “quadrupole distortion.” For example, if matter is stretched in the vertical direction, gravitational waves will compress it in the horizontal direction and vice versa.

Gravitational waves don't get distorted or altered by interactions with matter as they race through space; they therefore carry "pure" information about the objects and events that created them.

The earliest source of gravitational waves is not the Big Bang, but rather cosmological inflation: a period during which the universe underwent a brief flash of exponential expansion just after the Big Bang. When light waves vibrate in a certain direction, we say that it has a specific polarization. If gravitational waves were present at the time when the CMB was born, they should leave behind a unique swirly pattern – a curling in the polarization of the light – dubbed "B modes."

New Windows on the Universe

No one knew for sure if black holes actually merged together to create even more-massive black holes, now there's physical proof.

The detection of gravitational waves give humanity the ability to see the universe in a totally new way.

An entirely new realm of information is now available. Gravitational waves are used to detect some of the most violent processes in the universe: merging black holes and/or neutron stars, or the core region of supernova explosions. In some cases, gravitational waves are the only way to learn about these situations. For example, we are able to look at the actual dynamics of what goes on inside the supernova. While light is often blocked by dust and gas, gravitational waves come right out of the supernova, boldly unimpeded. As a consequence, you really find out what's going on inside of these things. Likewise, scientists aren't sure what happens to regular matter under such extreme conditions, but gravitational waves could provide extremely helpful clues, because these waves should carry information about the interior of the neutron star all the way to Earth

How the LIGO (Light Interferometer Gravitational Wave Observatory) Functions

There are two detectors that makes up the observatory one in Livingston, Louisiana and the other in Hanford, Washington.

LIGO is a ground-based observatory that uses laser interferometry to seek out gravitational waves. In 1994, the agency committed almost $300 million to a group led by Kip Thorne and Ron Drever of Caltech and Rainer Weiss of MIT to transform their prototypes into a full-blown gravitational wave observatory

As a gravitational wave passes through Earth, it squishes space in one direction and stretches it another direction. LIGO looks for that warping of space-time using two "L" shaped detector. Each arm of each detector is 2.48 miles (4 kilometers) long. Near the point where the two arms meet, a pulse of laser light is released down each arm simultaneously. The pulses travel down an arm, bounce off a mirror at the far end and come back near the starting point, at the crux of the "L."

If a gravitational wave passes by, it will compress one arm of the detector and stretch the other. As a result, the light beam traveling down the stretched arm will take slightly longer to get back to the starting point than will the light beam traveling the arm that has been compressed. If the same signal is spotted by both detectors, researchers can be confident the signal is real, and not the result of environmental conditions at one of the two sites. Recording the signal at two different locations also allows scientists to find the gravitational wave's source in the sky by triangulation.

To spot gravitational waves directly for the first time ever, scientists had to measure a distance change 1,000 times smaller than the width of a proton.

To put this kind of sensitivity into yet more perspective, LIGO technology is theoretically capable of measuring the distance from the sun to the nearest star, Proxima Centauri, which lies about 4.25 light-years away to a level of about the width of a human hair.

The Sept. 14 signal was spotted by both LIGO detectors, about 7 milliseconds apart.

Application to Everyday Life

General relativity provides an understanding how gravity influences the passing of time, and this information is necessary for GPS technology, which uses satellites that orbit further away from the gravitational pull of the Earth than people on the surface.

Before the Detection of Gravitational Waves in LIGO

In 2014, researchers using the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) telescope in Antarctica announced they had detected signatures of gravitational waves in the microwave light left over from the Big Bang (known as the cosmic microwave background). But that result fell apart when observations by Europe's Planck space observatory showed the alleged signatures were probably nothing but space dust.

Difference between Gravitational Waves and Gravity Waves

Gravitational Waves are, in their most basic sense, ripples in space-time. Einstein's theory of general relativity predicted them over a century ago and they are generated by the acceleration or deceleration of massive objects in the cosmos.

Gravity Waves are physical perturbations driven by the restoring force of gravity in a planetary environment. In other words, gravity waves are specific to planetary atmospheres and bodies of water