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Quartz_gravimeter_pendulums.jpg (664 × 542 pixels, file size: 38 KB, MIME type: image/jpeg)
Summary
| Description |
English: Photo of quartz gravimeter pendulums used in the gravimeter instrument designed by Gulf Research and Development Co. in 1929. Accurate to less than 1 milligal, the Gulf instrument was the most accurate commercial gravimeter into the 1950s. The pendulums are 10.7 inches long and had a period of about 0.89 sec. They were mounted in a sealed vacuum tank and swung synchronized, 180° out of phase, to cancel out swaying of the support. Fused quartz was used because of its small thermal expansion, but stray electrostatic charges on the pendulums had to be removed by exposure to a radioactive salt before use. Alterations to image: removed aliasing artifacts (striped lines) from scanning of original halftone image using GREYCstoration filter in Gimp. |
| Date | |
| Source | Downloaded 2009-05-09 from Victor F. Lenzen, Robert P. Multauf (1964) 'Paper 44: Development of gravity pendulums in the 19th century' in United States National Museum Bulletin 240: Contributions from the Museum of History and Technology, reprinted in Bulletin of the Smithsonian Institution, 1964, Smithsonian Institution Press, USA, p.337, fig.29 on Google Books. Credited in text to US Coast and Geodetic Survey. |
| Author | US Coast and Geodetic Survey |
| Permission (Reusing this file) |
Original work of US Government |
Licensing
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This work is in the public domain in the United States because it is a work prepared by an officer or employee of the United States Government as part of that person’s official duties under the terms of Title 17, Chapter 1, Section 105 of the US Code.
Note: This only applies to original works of the Federal Government and not to the work of any individual U.S. state, territory, commonwealth, county, municipality, or any other subdivision. This template also does not apply to postage stamp designs published by the United States Postal Service since 1978. (See § 313.6(C)(1) of Compendium of U.S. Copyright Office Practices). It also does not apply to certain US coins; see The US Mint Terms of Use.
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| This file has been identified as being free of known restrictions under copyright law, including all related and neighboring rights. | ||
File history
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 19:28, 12 December 2012 | | 664 × 542 (38 KB) | Quibik | Removed the moire. |
| 02:48, 29 May 2009 |  | 664 × 542 (32 KB) | Chetvorno | {{Information |Description={{en|Photo of quartz gravimeter pendulums used in the Gulf gravimeter instrument designed by Gulf Research and Development Co. in 1929. Accurate to less than 1 milligal, the Gulf instrument was the most accurate commercial grav |
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