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Gravitational Waves, the Einstein Centennial, and an Explanation by David Tennant

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Einstein and his famous theory of gravity - general relativity - are once again in the news. The LIGO-Virgo collaboration announced yesterday 11th February that they had directly detected gravitational waves for the first time. This brought worldwide excitement to the field of science.

Gravitational waves are ripples in the fabric of spacetime itself, and propagate as the result of violent events in the Universe, like black holes colliding or stars exploding as supernovae. Even events just after the Big Bang could have created an early type of gravitational waves that scientists refer to as "primordial gravitational waves". The event reported by the LIGO-Virgo collaboration is due to the collision of two black holes, that eventually merged into one larger black hole about 1.3 billion years ago.

Gravitational waves were predicted by Einstein's theory of gravity a hundred years ago, but had never been detected directly. A direct detection of gravitational waves is extremely difficult. Scientists at LIGO use a laser interferometer that bounces lasers back and forth, first splitting the laser beam and then recombining it. By looking at the structure of the recombined laser beam, scientists can measure minute changes in the laser path that could indicate that spacetime was slightly distorted. The telltale signature that a gravitational wave had passed through the experiment was finally detected last September, and announced yesterday following months of intensive verification by the LIGO-Virgo team.

LIGO stands for Laser Interferometer Gravitational-Wave Observatory. It is an international collaboration with over 1000 members, representing over 15 countries, and founded in 1997. This major discovery shows the importance of large, international and collaborative projects with long timescales for modern discoveries in physics.

Scientists around the world are delighted at the announcement, and many on twitter were using the hashtags #Einstein100, #gravitationalwaves and #LIGO to follow the announcement as it unfolded on a webcast press conference held in Washington, DC.

The breakthrough discovery will give astrophysicists "new eyes" with which to observe the Universe. Today, scientists observe the night sky by collecting light - or electromagnetic waves - with telescopes. This light can be in the visible part of the spectrum, just like the light we see with our eyes, or in wavelengths that are invisible to human eyes, for example in the microwave, x-ray, or infra-red. Now that the existence of gravitational waves has been confirmed, scientists hope to look at the Universe with "gravitational" eyes. This will provide an entirely new approach to study gravity, black holes and well as the Universe as a whole.

This is a very exciting time for science, as astrophysicists now have the technological tools to study Einstein's great theory in more detail - 100 years after he first developed it.

Einstein's theory of General Relativity has other major implications, including the need for dark matter and dark energy to explain current observations of distant galaxies. To celebrate the Einstein centennial and the importance of his major work, I hope you will enjoy this short animation narrated by former Dr. Who David Tennant, animated by the award-winning Eoin Duffy and co-written by director Jamie Lochhead and myself.

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