What on Earth is wrong with gravity?
BBC - Horizon - What on Earth is wrong with gravity?
Key concepts from the programme:
Telescope with BUILT IN Laser
1000 million billion photons go up
10 or 5 come back
very hard experiment
1 to 3 centimeters precision measurement of Moon distance
40 years of measurements show that actual orbit of moon is
different to that predicted by Newton.
Moon observation is about 10 meters off Newton predictions.
filmed 28 July 2007
Two galaxies previously named 957 and 561.
Identical spectrum = same galaxy,
light takes two paths.
Global Position system
south of Denver Colorado, GPS Headquarters.
In Orbit time itself runs at a different speed
than on the surface of Earth.
Extra corrections are regularly dialled-in.
stronger field = slower time ticks
weaker field = faster time ticks
N: black hole=time stops?
LIGO Gravitational Wave Observatory
4km tubes at 90 degrees laser-mirrors
No GWs have been found.
Particle physicist and ex D:Ream keyboard player Dr Brian Cox wants to know why the Universe is built the way it is. He believes the answers lie in the force of gravity. But Newton thought gravity was powered by God, and even Einstein failed to completely solve it. Heading out with his film crew on a road trip across the USA, Brian fires lasers at the moon in Texas, goes mad in the desert in Arizona, encounters the bending of space and time at a maximum security military base, tries to detect ripples in our reality in the swamps of Louisiana and searches for hidden dimensions just outside Chicago.
FILMING Road Trip Routing
- Flight London Heathrow via Chicago to New Orleans
- Drive to Livingston
- New Orleans, Louisiana – LIGO, the Laser Interferometer Gravitational Wave Observatory
- Flight New Orleans to Denver
- Drive Colorado Springs
- Colorado Springs, Colorado – GPS headquarters at Shriever Airforce Base
- Drive to Denver
- Flight to Chicago
- Drive to Geneva
- Chicago, Illinois – Fermilab, Tevatron Particle Accelerator
- Drive to Chicago
- Flight to Tucson
- Tucson, Arizona – Kitt Peak Observatory
- Drive to El Paso
- Drive to Fort Davis
- Fort Davis, Texas – McDonald Observatory
- Drive to El Paso
- Flight to San Francisco
- San Francisco, California
- Flight Home…
Particle physicist and ex D:Ream keyboard player Dr Brian Cox takes Horizon on a unique journey of discovery. Brian’s not content with his research at CERN, nor with his collaboration with Danny Boyle on Sunshine providing the inspiration for the character played by Cillian Murphy. Brian wants to discover why the universe is built the way it is and he believes the answers lie in the force of gravity.
Gravity is the thing that keeps our feet on the ground and it was the first force of nature we thought we really understood. Back in 1687, Sir Isaac Newton managed to distil gravity down to one short equation. With it, he could predict how bodies moved under its influence, how the moon orbits the Earth, how the planets orbit the sun and even how stars move about the night sky. But driving out into the wilds of Texas, Brian goes to the McDonald Observatory where astronomers have categorical evidence that Newton wasn’t entirely correct.
Back in 1969, it was Newton’s understanding of gravity that helped get Neil and Buzz to the sea of tranquility. When they came home., the left behind on the moon’s surface some very special mirrors which could be used to put Newton to the test. By firing a laser at these mirrors, scientists like Peter Schelus make incredibly accurate measurements of the distance from the Earth to the Moon. Taking readings over 40 years, we now have a phenomenally precise map of the orbit of the moon. But the orbit of the moon is different to that predicted by Newton. “…It turns out that simple Newton’s laws of gravity really don’t answer all of the questions. You’ve got to explain your observations and Newton’s gravitational theory just doesn’t do it anymore…” In other words, Newton got it wrong.
Although he had his equation, Newton never really had any idea how or even why gravity worked. He simply put that down to God. It was Albert Einstein who came up with a completely new understanding of the Universe and with it, the key to the workings of gravity.
Unlike Newton’s Universe which was pretty much had stuff wafting around empty space, Einstein Universe’s had an internal fabric in which all matter was embedded. This fabric was made of the 3 dimensions of space intricately linked with the fourth dimension of time - the spacetime. In Einstein’s universe, the planets, stars, galaxies actually warp, bend and distort the spacetime. “…Everything that happens in the universe effects the spacetime and the spacetime affects everything that happens in the universe...”
Brian heads out to the famous Kitt Peak Observatory just west of Tucson, Arizona. Looking deep into the heart of the Cosmos, some 7.8 billion light years from Earth, astronomers here witnessed what appeared to be two completely identical galaxies. This baffled them until they realized that there was an intermediate galaxy in the frame. According to Einstein, this nearer galaxy was physically bending the spacetime which caused the light coming from the far off galaxy to get bent, producing the multiple images we see from earth.
Einstein realized that his universe of bendable spacetime could explain the existence of gravity. With spectacular graphics, conceptualizing spacetime as never seen before, Brian explains that the Earth distorts spacetime, and it’s this curving of the fabric of the universe that creates the effect we feel as gravity. The bigger the mass, or the nearer you are to an object, the more curved the spacetime becomes, and so the stronger is the effect of gravity. This may sound like science fiction, but many of us use the bending of spacetime everyday, when we switch on our GPS Sat Nav.
Heading south of Denver, Brian uses the car’s GPS to navigate to the Global Positioning System HQ, a maximum security military instillation just outside Colorado Springs. Guided by Major Bandit Brandt, he is taken round the very room from which the whole GPS network is controlled. To keep the system working, the clocks onboard the satellites up in orbit have to be in synch with time on earth. But up in the reduced gravity of orbit, spacetime is bent in such a way that time ticks faster than time on earth. “…What Einstein said is that the stronger the gravitational field the slower time ticks and the weaker it is the faster time ticks…” For the GPS to work, the controllers have to dial in a time correction, otherwise GPS would drift by around 11km per day and be completely useless.
On Earth and throughout much of the Universe, Einstein’s idea of bending spacetime is an accurate description of how gravity works. But Einstein knew his theory of gravity doesn’t apply to the whole universe. It fails to work in the most violent and turbulent places in the cosmos.
In the swamps of Louisiana, scientists are trying to peer deep into the most brutal corners of the Universe. At the Laser Interferometer Gravitational Wave Observatory, head man Joe Giame explains how they hope to use something called ‘gravitational waves’ to observe violent cosmic phenomena. ‘Gravitational waves’ are believed to be created when the spacetime is violently churned up by fast moving massive objects, sending out waves in the spacetime. “…These waves are physical distortions in our reality. You know they really are stretching and contracting the space and time that we’re in…” But so far, this bit of Einstein’s understanding of gravity and how the Universe works has yet to be proved correct.
Einstein has no answers in the dark heart of a black hole, and his idea of gravity completely fails at the Big Bang, the beginning of time. Here the Universe was incredibly hot, incredibly dense, and incredibly small. Much as he tried, Einstein never managed to answer the question of how gravity works when things get very small. “…Einstein’s theory of relativity just can't provide the answer, the maths doesn't work on the smallest distance scales…” But Brian insists that we have to know how gravity works at the smallest distances, if we want to know how it all began.
Brian takes us into the dark world of subatomic particles and the quest for a quantum theory of gravity, a universal theory that will work everywhere in the Cosmos. Quantum mechanics predicts that the force of gravity is ultimately created by the transmission of a particle, which they’ve called the graviton.
Using the Tevatron Particle Accelerator just outside Chicago, scientist Greg Landsberg has been trying to create these illusive gravitons. But in this complex field of science, Greg has a significant challenge on his hands. “…Its amazing that the way to see the graviton is by not observing it, by observing it’s missing…” If gravitons are created, Greg believes they would instantly disappear, vanishing from our reality into alternative dimensions of space. Brian explains that “…what scientists like Greg are proposing is that there can be extra hidden unseen dimensions. It sounds ridiculous and it is impossible to picture, but theoretically It’s possible. And it’s also possible that gravitons can spend most of their time in their extra dimensions…”
For the time being, the quest to find the graviton, and with it the solution to the mystery of gravity continues. Brian is confident we are looking in the right places. “..The solution to a deeper understanding of gravity will certainly lie in the marriage of Einstein’s theory with the quantum theories of sub atomic particles…” But he concedes that “…If there are things that I listen to, you listen to that you think that I just don’t understand that, then you’re in good company because nobody understands it…”
By BBC News Online science editor Dr David Whitehouse
You think that light is fast? Well, think again. Sometimes it is slower than a crawl.
All schoolchildren know that light is the fastest thing there is. It zips along through empty space at 297,000 km per second (186,000 miles a second). Light from the Sun takes about eight minutes to reach us, from the Moon just over a second, and two million years from the nearest galaxy.
But now a Danish physicist and her team of collaborators have found a way to slow light down to less than 1.6 km per hour (one mile an hour) - slower than a slow walk.
The researchers, led by Dr Lene Hau of the Rowland Institute for Science, and Harvard University, both in the US, said last year that they had slowed light down to 60 km per hour (38 mph). Now, they have gone even further.
Addressing a conference in the US, Dr Hau said that you could almost send out a beam of light, go for a cup of coffee and return in time to see the light come out of the other side of her equipment. "You could almost touch it," she added.
The way Dr Hau and her team have slowed down light by a factor of 600 million or so is to use a group of atoms called a Bose-Einstein condensate (BEC). These atoms are cooled to a temperature of only a few billionths of a degree above absolute zero, the coldest possible temperature, at which all motion stops.
In a Bose-Einstein condensate, atoms are hardly moving at all. This means that according to the uncertainty principle that rules atoms, they are spread out and overlap. This results in a group identity for the collection of supercold atoms.
And when light passes through such an environment, it will slow down.
Physicists have known for a long time that the speed of light is reduced when it travels though any transparent medium, such as water or glass. Lenses, for example, focus light by allowing it to pass through different thicknesses, thereby slowing it down by differing amounts.
By firing co-ordinated beams of laser light through the BEC, Hau and colleagues have slowed light down to a crawl. Inside the BEC, the so-called refractive index (which measures the slowing of light) becomes enormous: as high as 100 trillion times greater than that of glass.
Slowing down light may have many practical uses in communications, signal processing, television displays and night-vision devices.
As Albert Einstein lay on his deathbed, he asked only for his glasses, his writing implements and his latest equations. He knew he was dying, yet he continued his work. In those final hours of his life, while fading in and out of consciousness, he was working on what he hoped would be his greatest work of all. It was a project of monumental complexity. It was a project that he hoped would unlock the mind of God.
"I want to know God's thoughts"
"I am not interested in this phenomenon or that phenomenon," Einstein had said earlier in his life. "I want to know God's thoughts – the rest are mere details." But as he lay there dying in Princeton Hospital he must have understood that these were secrets that God was clearly keen to hang on to. The greatest scientist of his age died knowing that he had become isolated from the scientific community; revered on the one hand, ridiculed for this quest on the other.
It was a journey that started 50 years earlier in Berne, Switzerland. Then - in his early 20s - he was a young man struggling to make his mark. His applications to universities throughout Europe had all been rejected. In the end his father had pulled strings to get him a job as a third class clerk evaluating the latest electrical gizmos.
But in his spare time he was formulating the most extraordinary scientific ideas. In a single year - 1905, a year that would become known as his miracle year – he published papers that would redefine how we see our world and universe.
Time is relative
He confirmed that all matter was composed of molecules – an idea that at the time was controversial. And most famously of all, he published the paper 'On the electrodynamics of moving bodies'. It contained his Theory of Special Relativity and suggested that time - something that had always thought to be unchanging and absolute – was relative. It could speed up or slow down depending on the speed you were travelling. From this paper would come an additional three pages, finished in September of the same year, that would contain the derivation of e=mc², the most famous mathematical equation ever written.
Einstein was on a roll. Ten years after his Theory of Special Relativity, he published his Theory of General Relativity – a piece of work widely acknowledged as his masterpiece. The great 17th century scientist Sir Isaac Newton had described the force of gravity very successfully, but what caused gravity remained a mystery. In this Theory of General Relativity, Einstein suggested that gravity was due to the bending of time and space by massive objects. In 1919 astronomers confirmed this by measuring the bending of starlight around the sun during a solar eclipse.
The battle with quantum mechanics
In 1921, Einstein was awarded the Nobel Prize, not for his theories of relativity, but for another paper published in 1905. In this paper, Einstein proposed that light was not simply made up of waves, it could also be thought of as discrete, individual particles or quanta. This discovery would revolutionise physics and chemistry, because it would become one of the foundations of a new science: quantum mechanics.
But during the 1920s the new science of quantum mechanics began to turn the tide against the way Einstein saw the world. Young pretenders in the field of physics had begun to emerge, such as Heisenberg, Bohr and Schrödinger, who are now some of the most famous figures in science. But at the time they were mavericks. They saw quantum mechanics as a brand new way of interpreting everything.
A core element to their new interpretation of the world was that at a fundamental level, everything was unpredictable. You could, for example, accurately tell the speed of a particle but not – at the same time – its position. Or its position but not its speed. It meant that precise predictions were impossible – the best you could hope for was a science based on probabilities.
God does not play dice
Einstein's work was underpinned by the idea that the laws of physics were an expression of the divine. This belief led him to think that everything could be described by simple, elegant mathematics and moreover, that once you knew these laws you could describe the universe with absolute accuracy. Einstein loathed the implications of quantum mechanics. It was a clash of ideologies.
The conflict reached a crescendo in the late 1920s at the Solvay Conference in Belgium. There Einstein clashed with the great Danish physicist Niels Bohr over the nature of the universe. Einstein constantly challenged Bohr over the implications of quantum mechanics, but never budged from his belief that "God does not play dice", meaning that nothing would be left to chance in the universe. To which the quantum mechanics community replied: "Einstein, stop telling God what to do with his dice."
The theory of everything
But Einstein had a trick up his sleeve. He had already begun a piece of work that he believed would ultimately replace quantum mechanics. It would become later known as his theory of everything – it was his attempt to extend general relativity and unite the known forces in the universe.
By completing this theory of everything Einstein hoped he would rid physics of the unpredictability at the heart of quantum mechanics and show that the world was predictable – described by beautiful, elegant mathematics. Just the way he believed God would make the universe. He would show that the way the quantum mechanics community interpreted the world was just plain wrong. It was a project that he would work on for the next 30 years, until the final day of his life.
But while Einstein's theory of everything may be considered to have been a failure, it is an idea that still fascinates and draws some of the brightest minds in physics. Today many believe that String Theory is our best candidate for a theory of everything. But the ultimate irony is that lurking at the heart of String Theory is the very thing that, because of his beliefs, Einstein had been unable to accept: quantum mechanics.
Good, concise introduction:
'Einstein', Peter D Smith, (Life&Times series) Haus Publishing, ISBN 1-904341-15-2
In depth and authoritative biography focusing on Einstein's science:
'Subtle is the lord', Abraham Pais, OUP, ISBN 0-19-285138-1
The Bohr-Einstein debate:
'Einstein Defiant - genius vs genius in the quantum revolution', Edmund Blair Bolles, Joseph Henry Press, 0-309-08998-0
Words of wisdom:
'The Expanded Quotable Einstein, Alice Calaprice, PUP, ISBN 0-691-07021-0
Einstein's Cosmos, Michio Kaku, Orion, ISBN 0-297-84755-4