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NS: Instant Expert: General relativity

Post by bystander » Wed Jun 30, 2010 6:35 pm

Instant Expert: General relativity
New Scientist | 30 June 2010
Instant Expert: General relativity
  1. PAST, PRESENT AND FUTURE

    Albert Einstein's general theory of relativity is one of the towering achievements of 20th-century physics. Published in 1916, it explains that what we perceive as the force of gravity in fact arises from the curvature of space and time.

    Einstein proposed that objects such as the sun and the Earth change this geometry. In the presence of matter and energy it can evolve, stretch and warp, forming ridges, mountains and valleys that cause bodies moving through it to zigzag and curve. So although Earth appears to be pulled towards the sun by gravity, there is no such force. It is simply the geometry of space-time around the sun telling Earth how to move.

    The general theory of relativity has far-reaching consequences. It not only explains the motion of the planets; it can also describe the history and expansion of the universe, the physics of black holes and the bending of light from distant stars and galaxies.

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    EINSTEIN'S INSIGHT

    How Einstein moved from his 1905 special theory of relativity to general relativity a decade later, via a brainwave he had at his day job.
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    PHYSICIST, SUPERSTAR

    Einstein's theory was confirmed and the physicist himself won worldwide fame when a 1919 solar eclipse allowed his predictions to be put to the test.
  2. HOW GENERAL RELATIVITY SHAPES OUR UNIVERSE

    Einstein's general theory of relativity has revealed that the universe is an extreme place. We now know it was hot and dense and has been expanding for the past 13.7 billion years. It is also populated with incredibly warped regions of space-time called black holes that trap anything falling within their clutches.

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    BLACK HOLES

    What happens when extreme gravity pierces the fabric of space-time? There's a monster example at each galaxy's heart.
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    THE EXPANDING UNIVERSE

    Einstein wasn't happy with the idea of a big bang – until astronomer Edwin Hubble showed that galaxies are speeding away from each other.
  3. FRONTIERS OF GENERAL RELATIVITY

    General relativity predicts that the universe is full of exotic phenomena. Space-time can tremble like the surface of a pond and it seems to be full of a mysterious form of energy that is pushing it apart. It is also conceivable for space-time to be so warped that it becomes possible to travel backwards in time.

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    GRAVITATIONAL WAVES

    Even empty space-time, devoid of stars and galaxies, can have a life of its own.
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    THE DARK UNIVERSE

    The universe isn't behaving as it should – that's why astronomers and cosmologists think it's dominated by unseen dark matter and dark energy.
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    QUANTUM GRAVITY

    The big unsolved problem of modern physics is reconciling its two pillars: general relativity and quantum mechanics. Quantum gravity would unite them.

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