# Shielding (gravitation)

The shielding of gravitation (also absorption of gravitation ) is a hypothetical process in which an object is shielded - at least partially - from the influence of the gravitational field , which is supposed to lead to a reduction in the weight of the object.

No experiment recognized and repeatedly reproduced by experts has so far been able to produce positive shielding results. According to current knowledge, any shielding of gravitation is contrary to the principle of equivalence of the general theory of relativity by Albert Einstein , which has so far been confirmed in all experiments.

## Tests of the principle of equivalence

In order to quantify the magnitude of the shielding, Quirino Majorana proposed the coefficient h, which is intended to modify Newton's law of gravity in the following way:

${\ displaystyle F = {\ frac {GMm} {r ^ {2}}} e ^ {- h \ int \ rho (r) dr}}$

The best laboratory measurements have shown an upper shielding limit of 4.3 × 10 −15 m² / kg. However, astronomical observations suggest a much stricter limit. Based on observations of the lunar orbit of 1908, Henri Poincaré stipulated that h should not be larger than 10 −18 m² / kg. This limit has also been specified in the meantime. Eckhardt (1990) set an upper limit of 10 −22 m² / kg, and Williams, et al., (2006) increased this to h = (3 ± 5) × 10 −22 m² / kg, although this value is smaller is than the measurement inaccuracy. For an overview of the current experimental limit values, see Bertolami, et al.

The consequence of these negative results (which are in good agreement with the general theory of relativity) is that any theory which includes a general shielding of gravity, e.g. B. the Le-Sage-Gravitation , is refuted or this effect has to reduce to an immeasurable size.

## Majorana's experiments and Russell's criticism

Quirino Majorana conducted several experiments around 1920 and claimed to have given a positive shielding result. Since Majorana was a well-known and respected experimental physicist, Henry Norris Russell responded to these results. He showed that, in his opinion, these results cannot have anything to do with a shielding of gravity, otherwise, using Majorana's value for h, the levels of the tides on the opposite part of the earth would be only half as high as on the side facing the sun.

If Majorana's measurement results are not due to measurement errors, Russell says another explanation must be sought. He therefore proposed a modification of the general theory of relativity (GTR), according to which the mass of one body should decrease in the vicinity of another body and whereby the principle of equivalence would be preserved. Russell emphasized, however, that this mass variation should not be understood as a shield against gravity. However, Russell's theory of mass variability in the context of GTR is not accepted by the professional world.

However, since an exact reproduction of the exact experimental setup of Majorana is not yet available, speculation continues. The negative results when checking the principle of equivalence (see the description above) make a gravitational effect appear rather unlikely in the professional world. See e.g. B. the explanation of Coïsson et al., Who believe in the positive outcome of the experiment, but reject any connection with a shielding of gravity.

For a historical overview of attempts to demonstrate a shield against gravitation, see the article by Martins.

## Views outside the mainstream

Although such concepts are largely rejected, z. B. NASA continues research in this direction.

The shielding experiments of Yevgeny Podkletnow with rotating superconductors , which are said to have turned out positive with a variation in weight of 0.5% to 2%, are also well known. This is a multiple of what was specified as the upper limit in the tests of the principle of equivalence. Podkletnov's results and justifications are therefore not accepted by the professional world and could not be confirmed by various experimenters. The effect he allegedly measured is also known as antigravity .

## Individual evidence

1. a b Bertolami, O. & Paramos, J. & Turyshev, SG (2006), General Theory of Relativity: Will it survive the next decade? , arxiv : gr-qc / 0602016 , in H. Dittus, C. Laemmerzahl, S. Turyshev, Lasers, Clocks, and Drag-Free: Technologies for Future Exploration in Space and Tests of Gravity : 27-67
2. a b Majorana, Q., (1920). “On gravitation. Theoretical and experimental researches ”, Phil. Mag. [Ser. 6] 39 , 488-504.
3. a b Unnikrishnan and Gillies (2000), Phys Rev D, 61
4. ^ Poincaré, H .: La dynamique de l'électron . In: Revue générale des sciences pures et appliquées. 19, 1908a, pp. 386-402. Reprinted in Poincaré, Oeuvres, tome IX, pp. 551-586; German translation in "Wissenschaft und Methode" (1908), third book.
5. ^ DH Eckhardt, Phy Rev D, 42, 1990, 2144
6. Williams, et al .: Testing the Equivalence Principle on the Ground and in Space , (2006), Lecture Notes in Physics arxiv : gr-qc / 0507083
7. Russell, HN (1921): On Majorana's theory of gravitation . Astrophys. J. 54, 334-346. bibcode : 1921ApJ .... 54..334R
8. Coïsson, R .; Mambriani, G .; Podini, P. A new interpretation of Quirino Majorana's experiments on gravitation and a proposal for testing his results , Il Nuovo Cimento B, vol. 117, Issue 04, p.469. bibcode : 2002NCimB.117..469C
9. Martins, de Andrade, R., 1999. “ The search for gravitational absorption in the early 20th century ”, in: The Expanding Worlds of General Relativity (Einstein Studies, vol. 7) (eds., Goemmer, H., Renn , J., and Ritter, J.), Birkhauser, Boston, pp. 3-44.
10. N. Li, D. Noever, T. Robertson, R. Koczor and W. Brantley, Static Test for a Gravitational Force Coupled to Type II YBCO Superconductors , Physica C 281, 260-267
11. R. Koczor and D. Noever, Fabrication of Large Bulk Ceramic Superconductor Disks for Gravity Modification Experiments and Performance of YBCO Disks Under em Field Excitation , NASA Marshall, Huntsville, AL, AIAA 99-2147, 35th AIAA / ASME / SAE / ASEE Joint Propulsion Conference, June 20-24, 1999, Los Angeles, CA.
12. Space.com on NASA funding ( Memento from February 6, 2010 in the Internet Archive )
13. American Anti Gravity ( Memento December 7, 2002 in the Internet Archive ), Podkletnov's Original Paper
14. Li, N., Noever, D., Robertson, T., Koczor, R., and Brantley, W., "Static Test for a Gravitational Force Coupled to Type II YBCO Superconductors," Physica C, 281, 260-267 , (1997).
15. Woods, C., Cooke, S., Helme, J., and Caldwell, C., "Gravity Modification by High Temperature Superconductors," Joint Propulsion Conference, AIAA 2001-3363, (2001).
16. ^ Hathaway, Cleveland, & Bao. 2003. Gravity modification experiment using a rotating superconducting disk and radio frequency fields. Physica C. 385: 488-500.