GRAVITATION ANOMALIES DURING SOLAR ECLIPSE
EXPEDITION
The next solar eclipse in Europe takes place in 29th March 2006 in Turkey. The solar eclipse starts on western part of South America, goes over Atlantic Ocean, passes through North Africa, continues on Mediteranian Sea to Turkey, further to Russian, and ends in Asian. This eclipse is total. The path of the totality passes over Turkey from southwest to northeast as can be seen in Fig. 3. The mean width of the totality path is 183 km and the maximal duration on the central line is 3 minutes and 45 seconds. The altitude of the sun-moon system during the eclipse is 55 degrees on the southern Mediterranean coastline of Turkey. All these figures make this eclipse a good candidate when searching eclipse related gravity anomalies.
Figure 3. The path of the total solar eclipse on 29th March 2006. The central path is marked with the red line and the edges by the black lines
The gravity measurements will be done simultaneously on 3 different places with equal instruments. The measurement locations have been positioned approximately on the L-shape grid, as shown in Fig. 4. One of the positions is on the edge of the totality path, and two on  the central line of the totality. The distance between adjacent positions is 50-75 km. Several simultaneous recording sites with identical measuring systems have never been used in previous attempts to capture gravity anomalies during the solar eclipse, and therefore it has been very difficult to verify the results afterwards. If any anomalies can be found, it can be assumed that they should be detectable on different locations and/or at different times. If positive results can be observed from multiple recording sites it would be very strong evidence on a real effect, which is not produced by spurious disturbances or interferences. The recording sites on the central line makes it possible to look at time correlations of the phenomenon, and the recording sites on the perpendicular line position correlations.
Figure 4. The measurement locations are Antalya, Manavgat and Akseki. The path of the totality is marked as in Fig. 3.
The headquarter of the expedition is in Antalya, the city found on the southern coastline of Turkey. Antalya is located on the path of totality. Antalya has been selected since it has the airport and from there it is easy to travel toward the central line of the eclipse trough the coastline roads and further inland along the central line. Two other measurement locations are the cities of Manavgat and Akseki.

The eclipse expedition will be realized using 3 measurement groups. In each group there are two persons, and each group is provided by equal instrumentation. The instrumentation package consists of the double pendulum gravimeter, laptop microcomputer for data recording, the power supply unit and other equipment. Every measurement group has its own car to go to the observation location. Recordings of each group will be time-aligned by synchronization of the microcomputer clocks, this accuracy is enough to capture minute scale phenomenon. In addition to gravitiation measurements also the local temperature and pressure and the strength of the magnetic field in the horizontal plane are recorded. Communication between the measurement groups will be arranged by mobile phones. The accurate coordinates of each measurement location are determined by GPS device.

The voluntary persons for the measurement groups will be recruited half a year before the eclipse day from the staff and students of Department of Physics in University of Turku. Since smooth and reliably function of all members of the groups on the eclipse day is crucial, groups will be trained several times before March 2006.

Previous observations on gravity anomalies have been performed using various methods, like paraconical pendulum, torsion pendulum and gravimeters. As we shown in the previous chapter, all positive results can be explained either by inclination of the normal gravity vector, inclination of the measurement system or generation of small additional horizontal gravity component. Systems used previously are differently sensitive on these possible effects. Therefore we have planned to use an instrument, which directly measures the horizontal component of the gravity field. A normal pendulum can be used to perform this measurement but we have decided to use more advanced construction, so called double pendulum with magnetic coupling, which has much higher sensitivity. Our gravimeter can measure both the magnitude and direction of the horizontal gravity vector. This has not been done previously during any solar eclipses.

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