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Einstein was right: Space and time bend
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| HardTranceProd |
http://observer.guardian.co.uk/uk_n...2057529,00.html
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Einstein was right: space and time bend
Ninety years after he expounded his famous theory, a $700m Nasa probe has proved that the universe behaves as he said. Now the race is on to show that the other half of relativity also works
Under his name in the Oxford English Dictionary is the simple definition: genius. Yet for decades physicists have been asking the question: did Albert Einstein get it wrong? After half a century, seven cancellations and $700m, a mission to test his theory about the universe has finally confirmed that the man was a mastermind - or at least half proved it.
The early results from Gravity Probe B, one of Nasa's most complicated satellites, confirmed yesterday 'to a precision of better than 1 per cent' the assertion Einstein made 90 years ago - that an object such as the Earth does indeed distort the fabric of space and time.
But this - what is referred to as the 'geodetic' effect - is only half of the theory. The other, 'frame-dragging', stated that as the world spins it drags the fabric of the universe behind it.
Francis Everitt, the Stanford University professor who has devoted his life to investigating Einstein's theory of relativity, told scientists at the American Physical Society it would be another eight months before he could measure the 'frame-dragging' effect precisely.
'Understanding the details is a bit like an archeological dig,' said William Bencze, programme manager for the mission. 'A scientist starts with a bulldozer, follows with a shovel, then finally uses dental picks and toothbrushes to clear the dust away. We're passing out the toothbrushes now.'
The Gravity Probe B project was conceived in the late 1950s but suffered decades of delays while other scientists ran tests corroborating Einstein's theory. It was Everitt's determination that stopped it being cancelled. The joint mission between Nasa and Stanford University uses four of the most perfect spheres - ultra precise gyroscopes - to detect minute distortions in the fabric of the universe. Everitt's aim was to prove to the highest precision yet if Einstein was correct in the way he described gravity.
According to Einstein, in the same way that a large ball placed on a elasticated cloth stretches the fabric and causes it to sag, so planets and stars warp space-time. A marble moving along the sagging cloth will be drawn towards the ball, as the Earth is to the Sun, but not fall into it as long as it keeps moving at speed. Gravity, argued Einstein, was not an attractive force between bodies as had been previously thought.
Few scientists need the final results, which will be revealed in December, to convince them of Einstein's genius. 'From the most esoteric aspects of time dilation through to the beautiful and simple equation, e=mc2, the vast bulk of Einstein's ideas about the universe are standing up to the test of time,' said Robert Massey, from the Royal Astronomical Society.
He said the mission was 'legitimate science' to test a theory and confirm its brilliance, but others have criticised the costs and length of the study, claiming that what was announced had already been shown. Sir Martin Rees, the Astronomer Royal, said the announcement would 'fork no lightning'.
The theory explained
When Einstein wrote his general theory of relativity in 1915, he found a new way to describe gravity. It was not a force, as Sir Isaac Newton had supposed, but a consequence of the distortion of space and time, conceived together in his theory as 'space-time'. Any object distorts the fabric of space-time and the bigger it is, the greater the effect.
Just as a bowling ball placed on a trampoline stretches the fabric and causes it to sag, so planets and stars warp space-time - a phenomenon known as the 'geodetic effect'. A marble moving along the trampoline will be drawn inexorably towards the ball.
Thus the planets orbiting the Sun are not being pulled by the Sun; they are following the curved space-time deformation caused by the Sun. The reason the planets never fall into the Sun is because of the speed at which they are travelling.
According to the theory, matter and energy distort space-time, curving it around themselves. 'Frame dragging' theoretically occurs when the rotation of a large body 'twists' nearby space and time. It is this second part of Einstein's theory that the Nasa mission has yet to corroborate.
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| Taranis |
Question from someone who knows little to nothing about science:
If your 'ball on the trampoline' analogy is accurate, then wouldn't the earth, in the fullness of time, be pulled into the sun? As the marble would eventually run out of the energy that keeps it moving, stop spinning, and fall in next to the bowling ball?
Just curious, science has never been my thing. |
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| HardTranceProd |
sorry it's not "my" explanation - the quote accidentally ended earlier than it should have :)
I fixed my post. |
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| DJ Shibby |
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The other, 'frame-dragging', stated that as the world spins it drags the fabric of the universe behind it.
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Tell me this man did not enjoy some very fine cannabis in his day! |
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| Krypton |
| quote: | Originally posted by Taranis
Question from someone who knows little to nothing about science:
If your 'ball on the trampoline' analogy is accurate, then wouldn't the earth, in the fullness of time, be pulled into the sun? As the marble would eventually run out of the energy that keeps it moving, stop spinning, and fall in next to the bowling ball?
Just curious, science has never been my thing. |
On the trampoline scale, perhaps, but on the cosmic scale, it would take a very very very long time for us to dive into the sun. In fact, it should be the sun that kills earth by growing into a 'Red Giant' near the end of its life. |
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| Renegade |
| quote: | Originally posted by Taranis
If your 'ball on the trampoline' analogy is accurate, then wouldn't the earth, in the fullness of time, be pulled into the sun? As the marble would eventually run out of the energy that keeps it moving, stop spinning, and fall in next to the bowling ball? |
It's an imperfect analogy. The only reason a bowling ball warps the shape of a trampoline is because of the gravitational pull of the Earth, which is also why if you tried to place a marble in "orbit" around it, it would just roll underneath the bowling ball. In space you haven't got that artificial influence.
The best way I've heard it described is to imagine that an object orbiting another object is just taking the path of least resitance along the contours of the fabric of space time warped by the bigger object. The reason why the Earth doesn't just "fall" into the sun is firstly because it will never run out of energy (unless something very big hits it - 1st law of thermodynamics) and secondly because it requires less force to keep the Earth in orbit around the sun (which is a very stable, balanced system) than it would to push the Earth into the sun, or to push it out of orbit altogether. |
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| Capitalizt |
Think of it like this:
ALL objects in a gravitational field fall at the same speed, regardless of how fast they are going.
This means if you shoot a bullet perfectly straight, it falls towards the ground at the exact same speed as if you had just dropped the bullet and let it fall to your feet.
Ok? Ok.
Now, Despite the fact that both bullets fall at the same speed, the bullet travelling at high speed (shot out of the gun) goes much farther every second.
Now...if you had a gun that could shoot a bullet say...8km/sec (escape velocity), and you shot it straight ahead, it would still be falling toward the ground at the same speed as always, but because it is going fast enough to take advantage of the earth's curvature, it would never hit the ground ;)
It is effectively in orbit at that speed. It is constantly falling towards the earth, but because the earth is round, it ends up falling "around" the planet instead of into it.
Of course, in reality your bullet would probably hit a person, a mountain, or a few dust particles that would provide resistance, slowing it down and causing it to fall to the surface...so it wouldnt stay in orbit forever. In space however, there is no resistance...just an empty vaccuum. There is nothing to slow down the earth's momentum, which is why we will continue falling "around" the sun forever. |
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