What are gravitational waves and why should you care?

Scientists on Thursday February 11,2016 announced that they had detected evidence of gravitational waves caused by two black holes colliding 1.3billion years ago in historic experiment proving the theory of general relativity
The discovery has been hailed as a milestone in quest to understand the cosmos.

The scientists said they first detected a gravitational wave on September 14. In this image, student Muzi Li at the Institute of Gravitational Research at Glasgow University holds a phone that shows a computer simulation of gravity waves

The gravitational waves were detected on Sept. 14, 2015, at 4:51 a.m. CDT by both of the twin Laser Interferometer Gravitational-wave Observatory, or LIGO, detectors, located in Livingston, La., and Hanford, Wash. 

The LIGO Observatories are funded by the National Science Foundation, or NSF, and were conceived, built and are operated by Caltech and MIT.

The near simultaneous detection was necessary to confirm that the event was real, and indicated based on the relative time of arrival of the signals traveling at the speed of light, that the source was located in the southern hemisphere sky. 

The LIGO detectors are interferometers that shine a laser through a vacuum down two arms in the shape of an L that are each 4 kilometers in length. 

The light from the laser bounces back and forth between mirrors on each end of the L. Scientists measure the length of both arms using the light.

If there's a disturbance in space-time, such as a gravitational wave, the time the light takes to travel 4 kilometers will be slightly different in each arm making one arm look longer than the other.

LIGO scientists measure the interference in the two beams of light when they come back to meet, which reveals information on the space-time disturbance.

WHAT ARE GRAVITATIONAL WAVES 

Scientists view the the universe as being made up of a 'fabric of space-time'.

This corresponds to Einstein's General Theory of Relativity, published in 1916.

Objects in the universe bend this fabric, and more massive objects bend it more.

Gravitational waves are considered ripples in this fabric.

They can be produced, for instance, when black holes orbit each other or by the merging of galaxies.

Gravitational waves are also thought to have been produced during the Big Bang.

If found, they would not only confirm the Big Bang theory but also offer insights into fundamental physics.

For instance, they could shed light on the idea that, at one point, most or all of the forces of nature were combined into a single force. 

In March 2014, a team operating the Bicep2 telescope, based near the South Pole, believed they had found gravitational waves, but their results were proven to be inaccurate.

WHAT IS THE THEORY OF RELATIVITY? 

Gravitational waves were predicted under Albert Einstein's (pictured) General Theory of Relativity in 1916, but have since remained elusive

In 1905, Albert Einstein determined that the laws of physics are the same for all non-accelerating observers, and that the speed of light in a vacuum was independent of the motion of all observers - known as the theory of special relativity.

This groundbreaking work introduced a new framework for all of physics, and proposed new concepts of space and time.

He then spent 10 years trying to include acceleration in the theory, finally publishing his theory of general relativity in 1915.

This determined that massive objects cause a distortion in space-time, which is felt as gravity.

At its simplest, it can be thought of as a giant rubber sheet with a bowling ball in the centre.

As the ball warps the sheet, a planet bends the fabric of space-time, creating the force that we feel as gravity.

Any object that comes near to the body falls towards it because of the effect.

Einstein predicted that if two massive bodies came together it would create such a huge ripple in space time that it should be detectable on Earth.

It was most recently demonstrated in the hit film film Interstellar.

In a segment that saw the crew visit a planet which fell within the gravitational grasp of a huge black hole, the event caused time to slow down massively.

Crew members on the planet barely aged while those on the ship were decades older on their return.

The theory was most recently demonstrated in the hit film film Interstellar, in a segment that saw the crew visit a planet which fell within the gravitational grasp of a huge black hole, causing time to slow down massively, so crew members on the planet barely aged while those on the ship were decades older on their return

David Reitze, executive director of the Laser Interferometer Gravitational-Wave Observatories (LIGO)said "Ladies and gentlemen, we have detected gravitational waves"

 

Dr. David Reitze, Executive Director of the LIGO Laboratory at Caltech, shows the merging of two black holes at a news conference to discuss the detection of gravitational waves, ripples in space and time hypothesized by physicist Albert Einstein a century ago

Five Things About Gravitational Waves

• Gravitational waves are ripples that travel at the speed of light through the fabric of space-time.
• Albert Einstein predicted the existence of gravitational waves in his general theory of relativity a century ago, and scientists have been attempting to detect them for 50 years.
• On Thursday, February 11, 2016, physicists from the Laser Interferometer Gravitational-wave Observatory (LIGO) announced that they had detected gravitational waves from a black hole collision, proving Einstein was right. The LIGO detections represent a much-awaited first step toward opening a whole new branch of astrophysics
• Prior to the direct detection of gravitational waves, there was indirect evidence for their existence. For example, measurements of the Hulse–Taylor binary system suggest that gravitational waves are more than a hypothetical concept.
• The historic detection of gravitational waves may open a new era of astronomy in which gravitational waves are tools for studying the most mysterious and exotic objects in the universe

What are gravitational waves?

Albert Einstein predicted gravitational waves in his general theory of relativity a century ago. They are ripples in space-time, the very fabric of the Universe.

The game-changing theory states that mass warps space and time, much like placing a bowling ball on a trampoline.

Other objects on the surface will "fall" towards the centre -- a metaphor for gravity in which the trampoline is space-time

When objects accelerate, they send ripples along the curved space-time fabric at the speed of light -- the more massive the object, the larger the wave and the easier it would be for scientists to detect.

Gravitational waves do not interact with matter and travel through the Universe completely unimpeded.

The strongest waves are caused by the most cataclysmic processes in the Universe -- two black holes colliding, massive stars exploding, or the very birth of the Universe some 13.8 billion years ago.

Why would detection of gravitational waves be important?

Finding proof of gravitational waves will end the search for a key prediction in Einstein`s theory, which changed the way that humanity perceived key concepts like space and time.

If gravitational waves become detectable, this would open up exciting new avenues in astronomy -- allowing measurements of faraway stars, galaxies and black holes based on the waves they make.

So-called primordial gravitational waves, the hardest kind to detect, would boost another leading theory of cosmology, that of "inflation" or exponential expansion of the infant Universe.

Primordial waves are theorised to still be resonating throughout the Universe today, though feebly.

If they are found, they would tell us about the energy scale at which inflation ocurred, shedding light on the Big Bang itself.

Why are they so hard to find?

Einstein himself doubted gravitational waves would ever be detected given how tiny they are.

Ripples emitted by a pair of orbiting black holes, for example, would stretch a one-million-kilometre (621,000-mile) ruler on Earth by less than the size of an atom.

Waves coming from tens of millions of lightyears away would stretch and squeeze a four-kilometre light beam such as the ones used at the Advanced Laser Interferometer Gravitational Wave

Observatory (LIGO) at the centre of Thursday February 11,2016's announcement, by about the width of a proton.

Laser Interferometer Gravitational-Wave Observatories (LIGO)