Tuesday, December 1, 2009
Thursday, November 19, 2009
Kuhn’s thesis was that scientific ideas do not evolve slowly and continuously. Scientific paradigm changes often take place through sudden dramatic shifts which occur when least expected. These changes usually sneak up on society and take everyone by surprise since the old paradigm is the one embraced by society's power elite, or in our day, by the Departmental Chairmen, the tenured professors and Heads of labs. The old belief system is able to maintain itself till the last minute. Once a new way of thinking reaches a tipping point, however, its changes can be immediate and profound.
Sometimes there may be an early indication which may be thought of as being only an interesting curiosity. Madame Curie was enchanted and delighted by the pretty blue light given off in the dark by her radioactive isotopes. This was something entirely new and unexpected. In terms of the prevailing 19th Century theories of matter and physics, the light was anomalous – there was no explanation for its source. No one could have imagined the significance this blue light would have 40 years later, when physical theories had been developed to explain it, the same theories which would permit the creation of nuclear bombs.
Einstein’s relativity theory is one of the foundational paradigms of today’s model of the physical universe. It seems to have withstood all challenges carried out over the past 80 years. When an astronomical result is obtained that varies from what is expected by relativity, this is called an “anomaly”, and it is automatically assumed there must be a hidden “second-order phenomena” which, when found, will explain the anomaly. But what happens when no explanation can be found? Scientists usually assume that given enough time they will find the explanation. So far this has been true. But sometimes, as in the case of Madame Curie’s blue light, the phenomenon can only be explained after a fundamental overhaul of the underlying physical theory.
The Pioneer Anomaly
In 1972 the US launched a spacecraft named the Pioneer 10 having a mission to travel across the solar system and take pictures of Jupiter and its moons before racing out of the solar system into interstellar space. The following year, in 1973, Pioneer 11 was launched on a similar mission, to rendezvous with Saturn to photograph its rings, and afterwards, to head out of the solar system into space. At the time of their launch, rocket technology was not available which could propel a spacecraft from earth at a sufficient speed to enable it to escape from the sun's gravity and reach outer space. On board ion-thruster propulsion systems had not yet been invented. But the gravitational field of a planet could be used to increase speed of a craft, employing “slingshot technology”, in which the spacecraft first was allowed to accelerate towards the planet, and then, avoiding collision, made to fly away at a greater speed.
Pioneer 10, after leaving earth, was able to reach escape velocity after it performed a gravity assist flyby around Jupiter. A year later, Pioneer 11 also used a flyby around Jupiter to propel it back inside the solar system with sufficient velocity to reach Saturn 5 years later and then afterwards to head out of the solar system in an opposite direction to that taken by Pioneer 10.
Throughout their journeys from earth, around the planets and out into space, the location of the two Pioneer craft and their speed could be measured with extreme accuracy using a technique known as Doppler radar which had been developed and highly refined for military use and for air traffic control. Both Pioneer missions were documented in detail and both returned images of stunning beauty back to earth.
Then, after heading into space, something totally unexpected was discovered! Doppler tracking data from the spaceships showed there was an anomalous shift in wavelength towards the blue in the radiation received back on earth from the spacecraft. The anomalous effect was continuous and did not vary. Something unknown was causing each spacecraft to loose a distance of about 1000 meters per day from its calculated flight path. The tracking data, which was accurate to one part per trillion, was subsequently analyzed over the next 14 years using the most sophisticated computer algorithms, taking into account all the known forces that could affect the motion of the spacecraft, but no property of the solar system was found which could provide an explanation for the acceleration.
Scientists in many mathematical and scientific disciplines were encouraged to propose explanations for the errant behavior of the spaceships. All of the positioning data was made public. Over the past 30 years, more than 124 peer reviewed scientific papers were published, offering a wide range of explanations for the Doppler blue shift, from exotic new gravitational effects arising from dark matter, dark energy, the effects of stellar bodies in the Kuiper belt, drag of the interplanetary medium, dust, solar wind, cosmic rays, electromagnetic forces from possible hard-to-detect electric charges in the spacecraft, and innumerable others.
And of course a number of papers were published suggesting that the laws of physics themselves may need to be amended. A modification of the law of gravity, or of inertia, or a MOdified Newtonian Dynamics (MOND). Some scientists suggested that a new theory of gravity may be required in which the spin of an object is able to change the value of G, which would be an effect not accounted for by Einstein in relativity theory. Other hypotheses have been put forward which incorporate mathematical models derived from String Theory and M-Theory which can explain the anomaly by assigning special constants to higher dimensions of space. Sorting out these competing theories will require new evidence from experiments which will need to be carried out in the future.
But there is yet another intriguing possibility. Are the anomalous blue shifts recorded from the Pioneer spaceships the first sign of a profound change that is to come? Could they be like Madame Curie’s little blue light, seemingly innocent, but in fact presaging what will turn out to be a radical change in our deepest understanding of the nature of the physical world? Are we now on the brink of a transition, in which our current mathematical models of gravity, mass, and energy may need to be upgraded? Will the discovery of new particles by the Large Hadron Collider become part of a new vision of physics?
FIVE MORE FLYBY ANOMALIES
On March 3, 2008 in Physical Review Letters five senior scientists at the Jet Propulsion Laboratory in Pasadena reported what they characterized as “anomalous orbital-energy changes” accurately observed in six separate Earth flybys by the spacecrafts Galileo, NEAR, Cassini, Rosetta, and MESSENGER. The authors said, “Like the Pioneer anomaly, and perhaps even more surprising, the Earth flyby anomaly is a real effect. . . . . . . . Its source is unknown.”
These flyby anomalies may end up being the harbingers of a profound paradigm change in physics.