How do planets create gravity

On the trail of the secrets of gravity

Agency
30/09/20021401 views0 likes

An epochal breakthrough may soon be imminent in physics. The European Space Agency ESA is currently preparing a number of unique interplanetary missions and experiments to unravel the unsolved mysteries of gravity. The results could lead to the previous notions of gravity being thrown overboard.

Enigmatic powers

Gravity is one of the four fundamental forces in nature. It shapes our universe and makes the formation of planets, stars and galaxies possible in the first place. The more intensively science deals with the phenomenon of gravitation and the influence of gravity on celestial bodies, the more questions arise. One example is the so-called Pioneer anomaly: When observing the NASA probes Pioneer 10 and 11, which were launched in 1972 and 1973 and have long since left our solar system, it was found that their flight speed did not meet expectations. Apparently some inexplicable force is slowing down the probes. The same effect can now also be seen in the Jupiter probe Galileo and the European-American solar probe Ulysses.

Gravity in abundance

Only matter can produce gravity, that is, gravity. But it has been known for a long time that there is more gravitational force in the universe than would be expected based on the apparent mass. In other words, in order to explain the observed gravitational forces, there would have to be far more matter in the universe than has been observed so far. Science therefore assumes that the depths of space hold large amounts of as yet undiscovered matter, the so-called dark matter.

According to other theories, gravitational forces act more strongly than previously thought over vast distances. If this were the case, the concept of dark matter would be dispensable. It is possible that the observed anomalies can also be traced back to a fifth, as yet unknown natural force, a very weak force that is only noticeable in the most distant regions of space.

Space is an ideal place to test such theories. In the weightlessness of space, the working of even the finest forces can be determined. In addition, extremely precise measurements are possible there.

Einstein put to the test

ESA is currently working on a series of highly ambitious space experiments and missions designed to test Einstein's general theory of relativity. With this theory, Einstein has so far most comprehensively and elegantly explained the phenomenon of gravitation. Among other things, Einstein's theory predicts a phenomenon that has never been observed before: light space tremors caused by so-called gravitational waves. Generated by accelerated cosmic masses - for example, neutron stars or black holes circling around each other - these small compressions and expansions of space propagate at the speed of light in space like concentric waves on a lake. ESA and NASA want to get to the bottom of this phenomenon with the probe trio LISA, which will start in 2011 and check space for the presence of gravitational waves. If such waves are registered, this would be conclusive proof of the correctness of the general theory of relativity.

Through further missions, the ESA wants to determine very precisely how the matter curves the space. With Gaia, a mission to map stars, and the Mercury mission BepiColombo, the aim is to determine whether the curvature of space is different from what general relativity predicts. And Microscope, a mission that ESA is preparing in collaboration with the French space agency CNES, is intended to test the equivalence principle postulated by Einstein. The principle states that all objects in a gravitational field are accelerated in the same way, regardless of their respective mass and chemical composition. Should microscope come across phenomena that run counter to this principle, this could point to a new dimension of gravity, quantum gravity.

The world of quanta

Scientists around the world are working feverishly on a conclusive theory of quantum gravity. The aim is to standardize the general theory of relativity and quantum mechanics, which describes all fundamental forces of nature with the exception of gravity. The concept of quantum gravity assumes that space is not smooth, but rather “granular” made up of the tiniest point particles. Almost like a beach, which from a distance also appears like a smooth surface, but actually consists of a myriad of individual grains of sand. The ESA space probe mission HYPER should track down this “point structure” of space as well as other gravitational phenomena. In addition, the European Space Agency has started to design another mission to investigate the Pioneer anomaly directly.

With this broad spectrum of missions, ESA will explore the nature of gravity on an unprecedented scale. It is very possible that this will result in groundbreaking discoveries that will completely turn our idea of ​​the universe on its head.

Information on the individual missions

LISA
LISA (Laser Interferometer Space Antenna) is a satellite-based laser interferometer in space for the detection and observation of gravitational waves that ESA is developing in cooperation with NASA. The detector consists of three space probes that circle the sun in a triangular configuration, each five million kilometers apart. The cosmic antennas are supposed to detect vibrations in the room, such as those emanating from super-heavy black holes. These vibrations, known as gravitational waves, were predicted by Einstein in his general theory of relativity. However, they have not yet been detected. For the first time, LISA attempts to measure these waves directly in space. The start of the LISA mission is planned for 2011.

Gaia
The aim of the Gaia mission, which is due to launch into space by 2012 at the latest, is to observe and map over a billion stars in our galaxy. Over a period of five years, the probe will record every observed star about 100 times and precisely record its movement and changes in brightness. In addition, Gaia is expected to discover hundreds of thousands of new celestial bodies, for example extrasolar planets and so-called brown dwarfs, which represent a "middle thing" between planet and star. And tens of thousands of as yet unknown asteroids are expected to be discovered in our solar system. In the course of exploring the celestial bodies, Gaia will also be able to determine exactly how matter bends space and thus deflects the light from the stars. Gaia should look for deviations from the curvature of space, which would be expected according to the general theory of relativity.

Microscope
The Microscope mission (MICROsatellite à Traînée Compensée pour l’Observation du Principe d’Equivalence) is intended to examine the equivalence principle of the general theory of relativity. The principle states that all objects, when exposed to a gravitational field, are subject to the same acceleration, regardless of their respective mass and composition. Microscope should determine whether this principle applies and has universal validity. Should the measurement results contradict this principle, this could indicate the working of a new, as yet unknown natural force or phenomenon and thus expand our knowledge of the nature of gravity and the laws of nature. Microscope is scheduled to start in 2005.

BepiColombo
The Mercury mission BepiColombo will consist of two orbiters and a lander, which will for the first time really comprehensively explore the planet closest to the sun in our system. The technologies for the mission, slated to launch in 2011, are currently being developed.
Among other things, BepiColombo is supposed to determine exactly how matter bends space and look for deviations from what the general theory of relativity predicts. With BepiColombo, Mars Express and Venus Express, ESA is the only space agency in the world that is currently planning missions to all planets in the inner solar system.

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