Gravitational waves: Why the fuss? (Update)

February 11, 2016
A Laser Interferometer Gravitational Wave Observatory optics technician inspects the equipment that will be used to conduct test
A Laser Interferometer Gravitational Wave Observatory optics technician inspects the equipment that will be used to conduct tests in Pasadena, February 10, 2016

Great excitement rippled through the physics world Thursday at the announcement that gravitational waves have been detected after a 100-year search.

Here's what it means.

Q: What are gravitational waves?

A: Albert Einstein predicted gravitational waves in his general theory of relativity a century ago. Under this theory, space and time are interwoven into something called "spacetime"—adding a fourth dimension to our concept of the Universe, in addition to our 3D perception of it.

Einstein predicted that mass warps space-time through its gravitational force. A common analogy is to view space-time as a trampoline, and mass as a bowling ball placed on it. Objects on the trampoline's surface will "fall" towards the centre—representing gravity.

When objects with mass accelerate, such as when two black holes spiral towards each other, they send waves along the curved space-time around them at the speed of light, like ripples on a pond.

The more massive the object, the larger the wave and the easier 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—black holes coalescing, massive stars exploding, or the very birth of the Universe some 13.8 billion years ago.

Albert Einstein (1879-1955), author of the theory of relativity, was awarded the Nobel Prize for Physics in 1921

Q: Why is the detection of gravitational waves important?

A: It ended the search for proof of a key prediction in Einstein's theory, which changed the way that humanity perceived key concepts like space and time.

Detectable gravitational waves open exciting new avenues in astronomy—allowing measurements of faraway stars, galaxies and black holes based on the waves they make.

Indirectly, it also adds to the evidence that black holes—never directly observed—do actually exist.

So-called primordial gravitational waves, the hardest kind to detect and not implicated in Thursday's announcement, 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.

Q: Why are gravitational waves they so elusive?

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

A: Einstein himself doubted gravitational waves would ever be detected given how small they are.

Ripples emitted by a pair of merging 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 deform a four-kilometre light beam such as those used at the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) by about the width of a proton.

Q: How have we looked for them?

A: Before now, gravitational waves had only been detected indirectly.

In 1974, scientists found that the orbits of a pair of neutron stars in our galaxy, circling a common centre of mass, were getting smaller at a rate consistent with a loss of energy through gravitational waves.

That discovery earned the Nobel Physics Prize in 1993. Experts say the first direct detection of gravitational waves is likely to be bestowed the same honour.

After American physicist Joseph Weber built the first aluminium cylinder-based detectors in the 1960s, decades of effort followed using telescopes, satellites and laser beams.

Earth- and space-based telescopes have been trained on cosmic microwave background, a faint glow of light left over from the Big Bang, for evidence of it being curved and stretched by gravitational waves.

Using this method, American astrophysicists announced two years ago they had identified gravitational waves using a telescope called BICEP2, stationed at the South Pole. But they later had to admit they made an error.

Another technique involves detecting small changes in distances between objects.

Gravitational waves passing through an object distort its shape, stretching and squeezing it in the direction the wave is travelling, leaving a telltale, though miniscule, effect.

Detectors such as LIGO at the centre of Thursday's news, and its sister detector Virgo in Italy, are designed to pick up such distortions in laser light beams.

At LIGO, scientists split the light into two perpendicular beams that travel over several kilometres to be reflected by mirrors back to the point where they started.

Any difference in length upon their return would point to the influence of gravitational waves.

Sources: European Space Agency, Institute of Physics, LIGO, Nature.

Explore further: Missing gravitational waves lead to black hole rethink

Related Stories

Missing gravitational waves lead to black hole rethink

October 21, 2015

Human understanding of galaxies and black holes is being called into question after an 11-year search for mysterious gravitational waves—famously predicted by Albert Einstein 100 years ago—failed to find anything.

Video: The hunt is on for gravitational waves

December 21, 2015

Gravitational waves are tiny distortions of space-time caused by some of the most violent cosmic events such as colliding black holes. The observation of these 'ripples of space-time' requires exquisitely sophisticated new ...

Gravitational wave rumors ripple through science world

January 12, 2016

Rumors are rippling through the science world that physicists may have detected gravitational waves, a key element of Einstein's theory which if confirmed would be one of the biggest discoveries of our time.

Recommended for you

Spherical tokamak as model for next steps in fusion energy

August 24, 2016

Among the top puzzles in the development of fusion energy is the best shape for the magnetic facility—or "bottle"—that will provide the next steps in the development of fusion reactors. Leading candidates include spherical ...

Feeling the force between sand grains

August 24, 2016

For the first time, Lawrence Livermore National Laboratory (LLNL) researchers have measured how forces move through 3D granular materials, determining how this important class of materials might pack and behave in processes ...

Understanding nature's patterns with plasmas

August 23, 2016

Patterns abound in nature, from zebra stripes and leopard spots to honeycombs and bands of clouds. Somehow, these patterns form and organize all by themselves. To better understand how, researchers have now created a new ...

Stretchy supercapacitors power wearable electronics

August 23, 2016

A future of soft robots that wash your dishes or smart T-shirts that power your cell phone may depend on the development of stretchy power sources. But traditional batteries are thick and rigid—not ideal properties for ...

4 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

baudrunner
3 / 5 (2) Feb 12, 2016
Einstein predicted that mass warps space-time through its gravitational force
Mass doesn't have gravitational force. Increase the velocity of a particle, and you increase its mass, but in effect you've increased its energy density. Increased density means that more space is displaced as a result. Gravity is the result of spatial displacement. You could say that a mass causes the displaced space to be curved around it, and that the result is a gravitational field around the mass, which when it overlaps the gravitational field of another mass, results in a cancellation of the volume between the two because of the 180° phase relationship that those respective fields have.

Go ahead and flag this as pseudo science if you like, but have a good think about it any way. Shock waves were detected which caused a ripple in space-time, but shock waves aren't gravity waves, because gravity has no EM wave characteristics.
nikola_milovic_378
1 / 5 (1) Mar 15, 2016
The right of the wonder that most people in science and almost all scientific institutions in a completely wrong way knowledge of the truth about the universe and its organization.
Everything that is related to the occurrence of BB, the spread of the universe, the curvature of space-time, dark matter, dark energy and much more, it really is a big mistake and the consequences of not accepting the existence of spiritual entities of the universe.
In this way, which denies the existence of the Creator of everything in the universe, including ourselves, will never be able to figure out all the floor above.
To facilitate understanding of the phenomenon, here's my notions:
 The universe is an infinite sphere filled substance ether, of which creates a substance under the influence of high-frequency ether, a hundred copies and orders the absolute consciousness of the universe (ACU), as the immense power of creation
nikola_milovic_378
1 / 5 (1) Mar 15, 2016
This creates strings of ether, in whose cross-section is formed of substances in the form of quarks and gluons and quarks, which are kept firmly associated special forces. In the further process of forming the subatomic particles, atoms, molecules, gas and gas clouds, heavenly bodies and clusters of galaxies.
Gravity is caused by unbalanced state between matter and ether and has a duty to re-assemble the material into a critical mass and to return it to its original state, in the ether, and it takes place through black holes.
Generally not exist the following items: BB, expansion of the universe, not "dark", the theory of relativity and Lorentz transformations are a mirage of those without personal consciousness, and consciousness is part of the spiritual entity of the universe (SEU). Because when we think, that has no idea what is religion, not to speak of the universe. It has nothing to do with religion.
nikola_milovic_378
1 / 5 (1) Mar 15, 2016
And science needs to go through its black hole, in order to understand what caused it and how we are able to do so because it is not our work.
There are two completely illogical statements with "evidence" of the existence of gravitational waves. The first; two black holes can never collide, because around them there are hundreds of billions of stars at distances of several hundred thousand light years.
The second is that the matter came before gravity, and beyond that space and time, which can not act on each other. The space is formed to accommodate the movement of matter, but the time to measure this movement and to determine the position of matter in this space.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.