Pioneer anomaly

Trajectories of the Pioneer and Voyager spacecraft. (The Pioneer anomaly is much too small to be noticeable at this scale.)

The Pioneer anomaly refers to deviations from projected courses for several spacecraft sent to the outer solar system. The data sent back from both Pioneer spacecraft, Galileo, and Ulysses, represent one of the first meaningful tests of the precision of gravitation predictions over long distances. The spacecraft have deviated from the courses which scientists predicted using general relativity, as well as Newtonian mechanics, indicating that both theories may be fundamentally flawed.

Discovery

Pioneer 10 and Pioneer 11 were space probes sent to study the planets Jupiter and Saturn. After following a hyperbolic trajectory around these planets, they had reached escape velocity for the solar system and were flying out. While their main mission was now ended, NASA stayed in radio contact with the craft to study the outskirts of the solar system.

Around the time of Pioneer 11's flyby of Saturn, it was found to be slightly off-course. (Every spacecraft sent to the outer solar system is intended to follow a specific course, predicted by the theory of general relativity. Radio transmissions and radar are used to track spacecraft to ensure that they stay on course.) While this in itself was within the range of error, astronomers continued tracking the craft to find that the anomalous sunward acceleration increased. Currently, Pioneer 10 and Pioneer 11 are respectively over 30 and 70 AU from the sun, the farthest any spacecraft has gone in near-free-fall. By using Doppler radar, scientists have found that the courses for both the Pioneer spacecraft show a constant acceleration towards the sun of beyond theoretical preditions.

Although the Galileo and Ulysses spacecraft showed some unexpected sunward acceleration, other unpredictable factors, such as the Yarkovsky effect and the thrust caused by radioactive material on board, prohibit any accurate measurement of the effect on these two spacecraft. The confounding effects are even more significant on the Voyager spacecraft, preventing even a discussion of whether the Pioneer Anomaly affects these craft at all.

The Pioneer anomaly is about 1000 times bigger than the two effects contributing to the difference between the acceleration predicted by general relativity and that predicted by classical (Newtonian) gravity. The effect of the increase in inertia due to the Lorentz transform is less than , and the difference in acceleration due to the Schwarzschild metric is also less than .

Explanations

Originally, scientists supposed that the Pioneer navigation code was in error. However, the code was verified by an independent team. After a rigorous search for all possible effects, the anomaly was determined to be real: the course actually does diverge from models.

Several possible explanations, some flawed, have been proposed for this effect:

In 2010, creation scientist Dr. D. Russell Humphreys wrote regarding his explanation for the Pioneer anomaly:

“

The only non-standard assumption I used was that the matter of the cosmos is limited in extent, with a fair amount of empty space beyond the matter—an assumption supported by the Bible. With those relatively modest beginnings, I was able to explain the Pioneer anomaly — it’s due to a change in the ‘fabric’ of space. In fact, this anomaly could be the first local manifestation we have observed of the expansion of the cosmos, and the first evidence that expansion is occurring in the present, not just the past. exas is the southernmost part of the Great Plains, which ends in the south against the folded Sierra Madre Occidental of Mexico. The continental crust forms a stable Mesoproterozoic craton which changes across a broad continental margin and transitional crust into true oceanic crust of the Gulf of Mexico. The oldest rocks in Texas date from the Mesoproterozoic and are about 1,600 million years old. These Precambrian igneous and metamorphic rocks underlie most of the state, and are exposed in three places: Llano uplift, Van Horn, and the Franklin Mountains, near El Paso. Sedimentary rocks overlay most of these ancient rocks. The oldest sediments were deposited on the flanks of a rifted continental margin, or passive margin that developed during Cambrian time. This margin existed until Laurasia and Gondwana collided in the Pennsylvanian subperiod to form Pangea. This is the buried crest of the Appalachian Mountains–Ouachita Mountains zone of Pennsylvanian continental collision. This orogenic crest is today buried beneath the Dallas–Waco—Austin–San Antonio trend. The late Paleozoic mountains collapsed as rifting in the Jurassic period began to open the Gulf of Mexico. Pangea began to break up in the Triassic, but seafloor spreading to form the Gulf of Mexico occurred only in the mid and late Jurassic. The shoreline shifted again to the eastern margin of the state and the Gulf of Mexico passive margin began to form. Today 9 to 12 miles (14 to 19 km) of sediments are buried beneath the Texas continental shelf and a large proportion of remaining US oil reserves are located here. At the start of its formation, the incipient Gulf of Mexico basin was restricted and seawater often evaporated completely to form thick evaporite deposits of Jurassic age. These salt deposits formed salt dome diapirs, and are found in East Texas along the Gulf coast.[21] East Texas outcrops consist of Cretaceous and Paleogene sediments which contain important deposits of Eocene lignite. The Mississippian and Pennsylvanian sediments in the north; Permian sediments in the west; and Cretaceous sediments in the east, along the Gulf coast and out on the Texas continental shelf contain oil. Oligocene volcanic rocks are found in far west Texas in the Big Bend area. A blanket of Miocene sediments known as the Ogallala formation in the western high plains region is an important aquifer.[22] Located far from an active plate tectonic boundary, Texas has no volcanoes and few earthquakes.[23] The assumption I used violently contradicts the foundational assumption of the big bang, which says the universe has no centre and no edge. In that model, the fabric of space would not change. Consequently, the big bang model has been unable to explain the anomalous Pioneer acceleration.

”

Other explanations offered:

• The anomalous acceleration could be due to the spacecraft venting energy in certain directions. However, such effects would be expected to be more significant earlier on, when the power sources were less degraded. The opposite was actually the case.
• Drag forces from the particles in space, analogous to air resistance, could be slowing the spacecraft down. While the average concentration of the particles is not high enough to produce the observed acceleration, the Pioneer spacecraft could conceivably have picked up an electric charge which could be attracting the particles.
• The theory of General Relativity and the Law of Universal Gravitation could be wrong; the gravitational force could be slightly stronger than predicted. In this context, it is important to note that other spacecraft flying in hyperbolic trajectories around celestial bodies have also experienced anomalous gravitational effects.
• There could be gravitational forces from other celestial bodies that have not been taken into account.
• A March 2011 paper claims that the anomaly is caused by heat radiation.[1]
• A Sept. 2011 paper claims that the anomaly has been shrinking, but is still a mystery.[2]

External links

• Pioneer anomaly by Creation Ministries International