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Tests der allgemeinen Relativitätstheorie

2009-09-20T19:37:23Z

Modify: /* Perihelion precession of Mercury */ seconds of arc -> arc seconds

{{General relativity}}
At its introduction in 1915, the [[general relativity|general theory of relativity]] did not have a solid empirical foundation. It was known that it correctly accounted for the "anomalous" [[precession]] of the [[perihelion]] of [[Mercury (planet)|Mercury]] and on philosophical grounds it was considered satisfying that it was able to unify [[Isaac Newton|Newton]]'s [[law of universal gravitation]] with [[special relativity]]. That light appeared to bend in gravitational fields in line with the predictions of general relativity was found in 1919 but it was not until a program of precision tests was started in 1959 that the various predictions of general relativity were tested to any further degree of accuracy in the weak gravitational field limit, severely limiting possible deviations from the theory. Beginning in 1974, [[Russell Alan Hulse|Hulse]], [[Joseph Hooton Taylor, Jr.|Taylor]] and others have studied the behaviour of [[binary pulsar]]s experiencing much stronger gravitational fields than found in our solar system. Both in the weak field limit (as in our solar system) and with the stronger fields present in systems of binary pulsars the predictions of general relativity have been extremely well tested locally.

On the largest spatial scales, such as [[galaxy|galactic]] and [[physical cosmology|cosmological]] scales, general relativity has not yet been subject to ''precision'' tests. Some have interpreted observations supporting the presence of [[dark matter]] and [[dark energy]] as a failure of general relativity at large distances, small accelerations, or small curvatures. The very strong gravitational fields that must be present close to [[black hole]]s, especially those [[supermassive black hole]]s which are thought to power [[active galactic nuclei]] and the more active [[quasar]]s, belong to a field of intense active research. Observations of these quasars and active galactic nuclei are difficult, and the interpretation of the observations are heavily dependent upon astrophysical models other than general relativity or competing fundamental [[Alternatives to general relativity|theories of gravitation]], but they are qualitatively consistent with the black hole concept as modeled in general relativity.

==Classical tests==

Einstein proposed three tests of general relativity, subsequently called '''the classical tests of general relativity''', in 1916:<ref name = Ein1916> {{cite journal| last = Einstein| first = Albert| authorlink = Albert Einstein| coauthors = | title = The Foundation of the General Theory of Relativity| journal = Annalen der Physik| volume = 49 | issue = | pages = 769–822| year = 1916| publisher = | url = http://www.alberteinstein.info/gallery/gtext3.html| format = PDF| id = | accessdate = 2006-09-03| doi = 10.1002/andp.19163540702 }}</ref>
# the perihelion precession of [[Mercury (planet)|Mercury]]'s orbit
# the [[gravitational lens|deflection of light]] by the [[Sun]]
# the [[gravitational redshift]] of light

===Perihelion precession of Mercury===

{{Details|Kepler problem in general relativity}}

In Newtonian physics, under [[Standard assumptions in astrodynamics]] a two-body system consisting of a lone object orbiting a spherical mass would trace out an [[ellipse]] with the spherical mass at a [[focus (geometry)|focus]]. The point of closest approach, called the [[periapsis]] (and for our Solar System in particular, [[perihelion]]), is fixed. There are a number of effects present in our solar system that cause the perihelions of the planets to precess, or rotate around the sun. These are mainly because of the presence of other planets, which perturb the orbits. Another effect is solar [[oblate]]ness, which produces only a minor contribution. The precession of the perihelion of Mercury was a longstanding problem in [[celestial mechanics]]. Careful observations of Mercury showed that the actual value of the precession disagreed with that calculated from Newton's theory by 43 arc seconds per century. A number of ''ad hoc'' and ultimately unsuccessful solutions had been proposed, but they tended to introduce more problems. In general relativity, this remaining [[Precession#Astronomy|precession]], or change of orientation within its plane, is explained by gravitation being mediated by the curvature of spacetime. Einstein showed that general relativity<ref name = Ein1916/> predicts exactly the observed amount of perihelion shift. This was a powerful factor motivating the adoption of general relativity.

Although earlier measurements of planetary orbits were made using conventional telescopes, the most accurate measurements are now made with [[Radar astronomy|radar]]. The total observed precession of Mercury is 5600 [[arc-second]]s per century with respect to the position of the [[vernal equinox]] of the Sun. This precession is due to the following causes (the numbers quoted are the modern values):

{| class="wikitable" border="1" style="margin-left:auto; margin-right:auto;"
|+'''Sources of the precession of perihelion for Mercury'''
|-
! Amount (arcsec/century) !! Cause
|-
| 5025.6 || Coordinate (due to the [[Precession#Precession of the equinoxes|precession of the equinoxes]])
|-
| 531.4 || Gravitational tugs of the other planets
|-
| 0.0254 || Oblateness of the Sun ([[quadrupole moment]])
|-
| 42.98±0.04 || General relativity
|-
| 5600.0 || Total
|-
| 5599.7 || Observed
|}

Thus, the predictions of general relativity perfectly account for the missing precession (the remaining discrepancy is within observational error). All other planets experience perihelion shifts as well, but, since they are further away from the Sun and have lower speeds, their shifts are lower and harder to observe. For example, the perihelion shift of Earth's orbit due to general relativity effects is about 5 seconds of arc per century. The periapsis shift has also been observed with [[radio telescope]] measurements of Binary pulsar systems, again confirming general relativity.

[[Image:1919 eclipse negative.jpg|right|thumb|250px|One of [[Sir Arthur Eddington|Eddington]]'s photographs of the 1919 [[solar eclipse]] experiment, presented in his 1920 paper announcing its success.]]

===Deflection of light by the Sun===

{{Details|Kepler problem in general relativity}}

[[Henry Cavendish]] in 1784 (in an unpublished manuscript) and [[Johann Georg von Soldner]] in 1801 (published in 1804) had pointed out that Newtonian gravity predicts that starlight will bend around a massive object.<ref>{{Cite journal |last=Soldner, J. G. v.
|year=1804 |title=[[s:de:Ueber die Ablenkung eines Lichtstrals von seiner geradlinigen Bewegung|Ueber die Ablenkung eines Lichtstrahls von seiner geradlinigen Bewegung, durch die Attraktion eines Weltkörpers, an welchem er nahe vorbei geht]] |journal=Berliner Astronomisches Jahrbuch |pages =161–172}}</ref> The same value as Soldner's was calculated by Einstein in 1911 based on the equivalence principle alone. However, Einstein noted in 1915 in the process of completing general relativity, that his (and thus Soldner's) 1911-result is only half of the correct value. So Einstein was the first to calculate the correct value for light bending.<ref>{{Cite journal |last=Will, C.M.|year=2006 |title=The Confrontation between General Relativity and Experiment |journal=Living Rev. Relativity |volume =9 |url=http://www.livingreviews.org/lrr-2006-3 |page=39}}</ref>

The first observation of [[light]] deflection was performed by noting the change in position of [[star]]s as they passed near the Sun on the [[celestial sphere]]. The observations were performed in 1919 by [[Sir Arthur Eddington]] and his collaborators during a total [[solar eclipse]],<ref> {{cite journal| last = Dyson| first = F. W.| authorlink = | coauthors = Eddington, A. S., Davidson C.| title = A determination of the deflection of light by the Sun's gravitational field, from observations made at the total eclipse of 29 May 1919| journal = Philos. Trans. Royal Soc. London | volume = 220A | issue = | pages = 291–333| year = 1920| publisher = | url = | id = | accessdate = }} </ref> so that the stars near the Sun could be observed. Observations were made simultaneously in the cities of [[Sobral, Ceará]], [[Brazil]] and in [[São Tomé and Príncipe]] on the west coast of [[Africa]].<ref> {{cite journal| last = Stanley| first = Matthew| authorlink = | coauthors = | title = 'An Expedition to Heal the Wounds of War': The 1919 Eclipse and Eddington as Quaker Adventurer| journal = Isis | volume = 94| issue = | pages = 57–89| year = 2003| publisher = | url = | id = | accessdate =| doi = 10.1086/376099 }} </ref> The result was considered spectacular news and made the front page of most major newspapers. It made Einstein and his theory of general relativity world famous. When asked by his assistant what his reaction would have been if general relativity had not been confirmed by Eddington and Dyson in 1919, Einstein famously made the quip: "Then I would feel sorry for the dear Lord. The theory is correct anyway." <ref>Citation: Rosenthal-Schneider, Ilse: Reality and Scientific Truth. Detroit: Wayne State University Press, 1980. p 74. See also Calaprice, Alice: The New Quotable Einstein. Princeton: Princeton University Press, 2005. p 227.)</ref>

The early accuracy, however, was poor. The results were argued by some<ref>[[Harry Collins]] and [[Trevor Pinch]], ''The Golem''', (ISBN 0521477360)</ref> to have been plagued by [[systematic error]] and possibly [[confirmation bias]], although modern reanalysis of the dataset<ref>Daniel Kennefick, "Not Only Because of Theory: Dyson, Eddington and the Competing Myths of the 1919 Eclipse Expedition," ''Proceedings of the 7th Conference on the History of General Relativity'', Tenerife, 2005; available [http://xxx.arxiv.org/abs/0709.0685 online from ArXiv]</ref> suggests that Eddington's analysis was accurate.<ref>Phillip Ball, "Arthur Eddington Was Innocent," ''Nature,'' 7 September 2007, doi:10.1038/news070903-20 (available [http://philipball.blogspot.com/2007/09/arthur-eddington-was-innocent-this-is.html online] 2007)</ref><ref name="PhysToday">D. Kennefick, "Testing relativity from the 1919 eclipse- a question of bias," ''Physics Today,'' March 2009, pp. 37-42.</ref> The measurement was repeated by a team from the [[Lick Observatory]] in the 1922 eclipse, with results that agreed with the 1919 results<ref name="PhysToday" /> and has been repeated several times since, most notably in 1973 by a team from the [[University of Texas]]. Considerable uncertainty remained in these measurements for almost fifty years, until observations started being made at [[radio astronomy|radio frequencies]]. It was not until the late 1960s that it was definitively shown that the amount of deflection was the full value predicted by general relativity, and not half that number.
The [[Einstein ring]] is an example of the deflection of light from distant galaxies by more nearby objects.

===Gravitational redshift of light===

Einstein predicted the [[gravitational redshift]] of light from the [[equivalence principle]] in 1907, but it is very difficult to measure astrophysically (see the discussion under ''Equivalence Principle'' below). Although it was measured by [[Walter Sydney Adams]] in 1925, it was only conclusively tested when the [[Pound-Rebka experiment]] in 1959 measured the relative redshift of two sources situated at the top and bottom of Harvard University's Jefferson tower using an extremely sensitive phenomenon called the [[Mössbauer effect]].<ref>{{cite journal|last=Pound| first=R. V.| coauthors = Rebka Jr. G. A. | authorlink = | date= November 1, 1959| title=Gravitational Red-Shift in Nuclear Resonance| journal=Physical Review Letters | volume = 3 | issue = 9 | pages=439–441 | url=http://prola.aps.org/abstract/PRL/v3/i9/p439_1| accessdate=2006-09-23| doi=10.1103/PhysRevLett.3.439| format=abstract}}</ref><ref>{{cite journal|last=Pound| first=R. V.| coauthors = Rebka Jr. G. A. | authorlink = | date= April 1, 1960| title=Apparent weight of photons| journal=Physical Review Letters| volume = 4 | issue = 7 | pages=337–341| url=http://prola.aps.org/abstract/PRL/v4/i7/p337_1| accessdate=2006-09-23| doi=10.1103/PhysRevLett.4.337| format=abstract}}</ref> The result was in excellent agreement with general relativity. This was one of the first precision experiments testing general relativity.

==Modern tests==
The modern era of testing general relativity was ushered in largely at the impetus of [[Robert H. Dicke|Dicke]] and [[Leonard Isaac Schiff|Schiff]] who laid out a framework for testing general relativity.<ref>{{cite journal|last=Dicke| first= R. H. | authorlink = | date= March 6, 1959| title=New Research on Old Gravitation: Are the observed physical constants independent of the position, epoch, and velocity of the laboratory? | journal=Science| volume = 129 | issue = 3349 | pages=621–624| url=http://www.sciencemag.org/content/vol129/issue3349/index.dtl| accessdate=2006-09-23| doi=10.1126/science.129.3349.621| pmid=17735811}}</ref><ref> {{cite conference| first = R. H. | last = Dicke| authorlink = | title = Mach's Principle and Equivalence| booktitle = Evidence for gravitational theories: proceedings of course 20 of the International School of Physics "Enrico Fermi" ed C. Møller | pages = | publisher = | year = 1962| location = | url = | doi = | id = | accessdate = }} </ref><ref>{{cite journal|last=Schiff| first= L. I. | authorlink = Leonard Isaac Schiff | date= April 1, 1960| title=On Experimental Tests of the General Theory of Relativity| journal=American Journal of Physics| volume = 28 | issue = 4 | pages=340–343| url=http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=AJPIAS000028000004000340000001&idtype=cvips&gifs=Yes| accessdate=2006-09-23| doi=10.1119/1.1935800}}</ref> They emphasized the importance not only of the classical tests, but of null experiments, testing for effects which in principle could occur in a theory of gravitation, but do not occur in general relativity. Other important theoretical developments included the inception of [[alternatives to general relativity|alternative theories to general relativity]], in particular, [[scalar-tensor theory|scalar-tensor theories]] such as the [[Brans-Dicke theory]];<ref>{{cite journal|last=Brans| first= C. H.| coauthors = Dicke, R. H.| authorlink = | date= November 1, 1961| title=Mach's Principle and a Relativistic Theory of Gravitation | journal=Physical Review| volume = 124 | issue = 3 | pages=925–935 | url=http://prola.aps.org/abstract/PR/v124/i3/p925_1| doi = 10.1103/PhysRev.124.925| accessdate=2006-09-23| format=abstract}}</ref> the [[parameterized post-Newtonian formalism]] in which deviations from general relativity can be quantified; and the framework of the [[equivalence principle]].

Experimentally, new developments in [[space exploration]], [[electronics]] and [[condensed matter physics]] have made precise experiments, such as the Pound-Rebka experiment, laser interferometry and lunar rangefinding possible.

===Post-Newtonian tests of gravity===
Early tests of general relativity were hampered by the lack of viable competitors to the theory: it was not clear what sorts of tests would distinguish it from its competitors. General relativity was the only known relativitistic theory of gravity compatible with special relativity and observations. Moreover, it is an extremely simple and elegant theory. This changed with the introduction of [[Brans-Dicke theory]] in 1960. This theory is arguably simpler, as it contains no [[dimensionless number|dimensionful]] constants, and is compatible with a version of [[Mach's principle]] and [[Paul Dirac|Dirac's]] [[Dirac large numbers hypothesis|large numbers hypothesis]], two philosophical ideas which have been influential in the history of relativity. Ultimately, this led to the development of the [[PPN formalism|parameterized post-Newtonian formalism]] by [[Kenneth Nordtvedt|Nordtvedt]] and [[Clifford Martin Will|Will]], which parameterizes, in terms of ten adjustable parameters, all the possible departures from Newton's law of universal gravitation to first order in the velocity of moving objects (''i.e.'' to first order in <math>v/c</math>, where ''v'' is the velocity of an object and ''c'' is the speed of light). This approximation allows the possible deviations from general relativity, for slowly moving objects in weak gravitational fields, to be systematically analyzed. Much effort has been put into constraining the post-Newtonian parameters, and deviations from general relativity are at present severely limited.

The experiments testing gravitational lensing and light time delay limits the same post-Newtonian parameter, the so-called Eddington parameter γ, which is a straightforward parameterization of the amount of deflection of light by a gravitational source. It is equal to one for general relativity, and takes different values in other theories (such as Brans-Dicke theory). It is the best constrained of the ten post-Newtonian parameters, but there are other experiments designed to constrain the others. Precise observations of the perihelion shift of Mercury constrain other parameters, as do tests of the strong equivalence principle.

===Gravitational lensing===
One of the most important tests is [[gravitational lensing]]. It has been observed in distant astrophysical sources, but these are poorly controlled and it is uncertain how they constrain general relativity. The most precise tests are analogous to Eddington's 1919 experiment: they measure the deflection of radiation from a distant source by the sun. The sources that can be most precisely analyzed are distant [[radio astronomy|radio sources]]. In particular, some [[quasar]]s are very strong radio sources. The directional resolution of any telescope is in principle
limited by diffraction; for radio telescopes this is also the practical limit. An important improvement in obtaining positional high accuracies (from milli-arcsecond to micro-arcsecond) was obtained by combining radio telescopes across the Earth. The technique is called [[VLBI|very long baseline interferometry]] (VLBI). With this technique radio observations couple the phase information of the radio signal observed in telescopes separated over large distances. Recently, these telescopes have measured the deflection of radio waves by the Sun to extremely high precision, confirming the amount of deflection predicted by general relativity aspect to the 0.04% level. At this level of precision systematic effects have to be carefully taken into account to determine the precise location of the telescopes on Earth. Some important effects are the Earth's [[nutation]], rotation, atmospheric refraction, tectonic displacement and tidal waves. Another important effect is refraction of the radio waves by the [[solar corona]]. Fortunately, this effect has a characteristic [[spectrum]], whereas gravitational distortion is independent of wavelength. Thus, careful analysis, using measurements at several frequencies, can subtract this source of error.

The entire sky is slightly distorted due to the gravitational deflection of light caused by the Sun (the anti-Sun direction excepted). This effect has been observed by the [[European Space Agency]] astrometric satellite [[Hipparcos]]. It measured the positions of about 105 stars. During the full mission about 3.5 × 106 relative positions have been determined, each to an accuracy of typically 3 milliarcseconds (the accuracy for an 8–9 magnitude star). Since the gravitation deflection perpendicular to the Earth-Sun direction is already 4.07 mas, corrections are needed for practically all stars. Without systematic effects, the error in an individual observation of 3 milliarcseconds, could be reduced by the square root of the number of positions, leading to a precision of 0.0016 mas. Systematic effects, however, limit the accuracy of the determination to 0.3% (Froeschlé, 1997).
===Light travel time delay testing===
[[Irwin I. Shapiro]] proposed another test, beyond the classical tests, which could be performed within the solar system. It is sometimes called the fourth "classical" test of [[general relativity]]. He predicted a relativistic time delay ([[Shapiro delay]]) in the round-trip travel time for radar signals reflecting off other planets.<ref>{{cite journal | last=Shapiro | first= I. I. | authorlink = | date= December 28, 1964| title=Fourth test of general relativity| journal=Physical Review Letters| volume = 13 | issue = 26 | pages=789–791| url= http://prola.aps.org/abstract/PRL/v13/i26/p789_1| accessdate= 2006-09-18| doi=10.1103/PhysRevLett.13.789| format=abstract}}</ref> The curvature of the path of a [[photon]] passing near the Sun is too small to have an observable delaying effect, but general relativity predicts a [[time]] delay which becomes progressively larger when the photon passes nearer to the Sun due to the [[time dilation]] in the [[gravitational potential]] of the sun. Observing radar reflections from Mercury and Venus just before and after it will be eclipsed by the Sun gives agreement with general relativity theory at the 5% level.<ref>{{cite journal | last=Shapiro | first= I. I. | authorlink = | coauthors = Ash M. E., Ingalls R. P., Smith W. B., Campbell D. B., Dyce R. B., Jurgens R. F. and Pettengill G. H.| date= May 3, 1971| title=Fourth Test of General Relativity: New Radar Result| journal=Physical Review Letters| volume = 26 | issue = 18 | pages=1132–1135| url= http://prola.aps.org/abstract/PRL/v26/i18/p1132_1?qid=d9cd6099c23f671e&qseq=7&show=25 | accessdate= 2006-09-22| doi=10.1103/PhysRevLett.26.1132| format=abstract}}</ref> More recently, the [[Cassini-Huygens|Cassini probe]] has undertaken a similar experiment which gave agreement with general relativity at the 0.002% level. Very Long Baseline Interferometry has measured velocity-dependent corrections to the Shapiro time delay in the field of moving Jupiter.<ref>{{cite journal | last=Fomalont |first= E.B.|authorlink = |coauthors = Kopeikin S.M.|date =[[November]] [[2003]]|title= The Measurement of the Light Deflection from Jupiter: Experimental Results|journal=Astrophysical Journal|volume=598|issue=1|pages=704-711|url=http://adsabs.harvard.edu/abs/2003ApJ...598..704F}}</ref><ref>{{cite journal | last=Kopeikin |first= S.M.|authorlink = |coauthors = Fomalont E.B.|date =[[October]] [[2007]]|title= Gravimagnetism, causality, and aberration of gravity in the gravitational light-ray deflection experiments|journal=General Relativity and Gravitation|volume=39|issue=10|pages=1583-1624 |url=http://adsabs.harvard.edu/abs/2007GReGr..39.1583K}}</ref>

===The equivalence principle===
{{Main|Equivalence principle}}

The equivalence principle, in its simplest form, asserts that the trajectories of falling bodies in a gravitational field should be independent of their mass and internal structure, provided they are small enough not to disturb the environment or be affected by [[tidal forces]]. This idea has been tested to incredible precision by [[Eötvös experiment|Eötvös torsion balance experiments]], which look for a differential acceleration between two test masses. Constraints on this, and on the existence of a composition-dependent fifth force or gravitational [[Yukawa interaction]] are very strong, and are discussed under [[fifth force]] and [[weak equivalence principle]].

A version of the equivalence principle, called the [[strong equivalence principle]], asserts that self-gravitation falling bodies, such as stars, planets or black holes (which are all held together by their gravitational attraction) should follow the same trajectories in a gravitational field, provided the same conditions are satisfied. This is called the [[Nordtvedt effect]] and is most precisely tested by the [[Lunar Laser Ranging Experiment]].<ref>{{cite journal | last=Nordtvedt Jr. | first= K. | authorlink = | date= May 25, 1968| title=Equivalence Principle for Massive Bodies. II. Theory
| journal=Physical Review | volume = 169 | issue = 5 | pages=1017–1025 | url= http://prola.aps.org/abstract/PR/v169/i5/p1017_1| doi = 10.1103/PhysRev.169.1017|accessdate= 2006-09-23| format=abstract}}</ref><ref>{{cite journal | last=Nordtvedt Jr. | first= K. | authorlink = | date= June 25, 1968| title=Testing Relativity with Laser Ranging to the Moon
| journal=Physical Review | volume = 170 | issue = 5 | pages=1186–1187 | url= http://prola.aps.org/abstract/PR/v170/i5/p1186_1| doi = 10.1103/PhysRev.170.1186accessdate=| format=abstract}}</ref> Since 1969, it has continuously measured the distance from several rangefinding stations on Earth to reflectors on the Moon to approximately centimeter accuracy.<ref>{{cite journal | last=Williams | first= J. G. | coauthors = Turyshev, Slava G., Boggs, Dale H. |authorlink = | date= December 29, 2004| title=Progress in Lunar Laser Ranging Tests of Relativistic Gravity
| journal=Physical Review Letters| volume = 93 | issue = 5 | pages=1017–1025 | url= http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PRLTAO000093000026261101000001&idtype=cvips&gifs=yes| doi = 10.1103/PhysRevLett.93.261101 | accessdate= 2006-09-23}}</ref> These have provided a strong constraint on several of the other post-Newtonian parameters.

Another part of the strong equivalence principle is the requirement that Newton's gravitational constant be constant in time, and have the same value everywhere in the universe. There are many independent observations limiting the possible variation of Newton's [[gravitational constant]],<ref>{{cite journal | last=Uzan | first= J. P. | authorlink = | year= 2003| title=The fundamental constants and their variation: Observational status and theoretical motivations
| journal=Reviews of Modern Physics| volume = 75 | issue = 5 | pages=403- | url= http://www.arxiv.org/abs/hep-ph/0205340| doi = 10.1103/RevModPhys.75.403| accessdate= 2006-09-23| format=abstract}}</ref> but one of the best comes from lunar rangefinding which suggests that the gravitational constant does not change by more than one part in 1011 per year. The constancy of the other constants is discussed in the [[Einstein equivalence principle]] section of the equivalence principle article.
====Gravitational redshift====
The first of the classical tests discussed above, the [[gravitational redshift]], is a simple consequence of the [[Einstein equivalence principle]] and was predicted by Einstein in 1907. As such, it is not a test of general relativity in the same way as the post-Newtonian tests, because any theory of gravity obeying the equivalence principle should also incorporate the gravitational redshift. Nonetheless, confirming the existence of the effect was an important substantiation of relativistic gravity, since the absence of gravitational redshift would have strongly contradicted relativity. The first observation of the gravitational redshift was the measurement of the shift in the spectral lines from the [[white dwarf]] star [[Sirius]] B by Adams in 1925. Although this measurement, as well as later measurements of the spectral shift on other white dwarf stars, agreed with the prediction of relativity, it could be argued that the shift could possibly stem from some other cause, and hence experimental verification using a known terrestrial source was preferable .

Experimental verification of gravitational redshift using terrestrial sources took several decades, because it is difficult to find clocks (to measure [[time dilation]]) or sources of electromagnetic radiation (to measure redshift) with a frequency that is known well enough that the effect can be accurately measured. It was confirmed experimentally for the first time in 1960 using measurements of the change in wavelength of gamma-ray photons generated with the [[Mössbauer effect]], which generates radiation with a very narrow line width. The experiment, performed by Pound and Rebka and later improved by Pound and Snyder, is called the [[Pound-Rebka experiment]]. The accuracy of the gamma-ray measurements was typically 1%. The blueshift of a falling photon can be found by assuming it has an equivalent mass based on its frequency <math>E=hf </math> (where ''h'' is [[Planck's constant]]) along with <math>E=mc^2</math>, a result of special relativity. Such simple derivations ignore the fact that in general relativity the experiment compares clock rates, rather than energies. In other words, the "higher energy" of the photon after it falls can be equivalently ascribed to the slower running of clocks deeper in the gravitational potential well. To fully validate general relativity, it is important to also show that the rate of arrival of the photons is greater than the rate at which they are emitted.
A very accurate gravitational redshift experiment, which deals with this issue, was performed in 1976,<ref>{{cite journal | last=Vessot | first= R. F. C.| coauthors = M. W. Levine, E. M. Mattison, E. L. Blomberg, T. E. Hoffman, G. U. Nystrom, B. F. Farrel, R. Decher, P. B. Eby, C. R. Baugher, J. W. Watts, D. L. Teuber and F. D. Wills| authorlink = | date= December 29, 1980| title=Test of Relativistic Gravitation with a Space-Borne Hydrogen Maser
| journal=Physical Review Letters | volume = 45 | issue = 26 | pages=2081–2084 | url= http://prola.aps.org/abstract/PRL/v45/i26/p2081_1| doi = 10.1103/PhysRevLett.45.2081
| accessdate= 2006-09-24| format=abstract}}</ref> where a [[hydrogen]] [[maser]] clock on a rocket was launched to a height of 10,000 km, and its rate compared with an identical clock on the ground. It tested the gravitational redshift to 0.007%.

Although the [[Global Positioning System]] (GPS) is not designed as a test of fundamental physics, it must account for the gravitational redshift in its timing system, and physicists have analyzed timing data from the GPS to confirm other tests. When the first satellite was launched, some engineers resisted the prediction that a noticeable gravitational time dilation would occur, so the first satellite was launched without the clock adjustment that was later built into subsequent satellites. It showed the predicted shift of 38 microseconds per day. This rate of discrepancy is sufficient to substantially impair function of GPS within hours if not accounted for. An excellent account of the role played by general relativity in the design of GPS can be found in Ashby 2003.

Other precision tests of general relativity, not discussed here,  are the [[Gravity Probe A]] satellite, launched in 1976, which showed gravity and velocity affect the ability to synchronize the rates of clocks orbiting a central mass; the [[Hafele-Keating experiment]], which used atomic clocks in circumnavigating aircraft to test general relativity and special relativity together;<ref>{{cite journal | last=Hafele | first= J. | coauthors = Keating, R. | authorlink = | date= July 14, 1972| title=Around the world atomic clocks:predicted relativistic time gains | journal=Science| volume = 177 | issue = 4044| pages=166–168| url= http://www.sciencemag.org/cgi/content/abstract/177/4044/166| doi = 10.1126/science.177.4044.166| accessdate= 2006-09-18| format=abstract| pmid=17779917}}</ref><ref>{{cite journal | last=Hafele | first= J. | coauthors = Keating, R. | authorlink = | date= July 14, 1972| title=Around the world atomic clocks:observed relativistic time gains | journal=Science| volume = 177 | issue = 4044| pages=168–170| url= http://www.sciencemag.org/cgi/content/abstract/177/4044/168 | doi = 10.1126/science.177.4044.168| accessdate=2006-09-18| format=abstract| pmid=17779918}}</ref> and the forthcoming [[STEP (satellite)|Satellite Test of the Equivalence Principle]].

===Frame-dragging tests===
The [[Gravity Probe B]] satellite, launched in 2004 and operating until 2005, attempted to detect [[frame-dragging]] (the Lense-Thirring effect). Data analysis continues as of October 2008; final results have been delayed, mainly due to high noise levels and difficulties in modelling the noise accurately so that a useful signal can be found.<ref>{{cite web |url=http://einstein.stanford.edu/ |title=Gravity Probe B: Testing Einstein's Universe |publisher=Stanford University |work= |accessdate=2008-10-19}}</ref> Tests of the [[Lense-Thirring]] effect, consisting of small secular precessions of the orbit of a test particle in motion around a central rotating mass like, e.g., a planet or a star, have been performed with the [[LAGEOS]] satellites<ref>{{cite journal | author = Ciufolini I. and Pavlis E.C.| title = A confirmation of the general relativistic prediction of the Lense-Thirring effect | journal = Nature |volume = 431 | year = 2004 |issue = 7011| pages = 958-960 | url=http://www.nature.com/nature/journal/v431/n7011/full/nature03007.html }}</ref>, but many aspects of them remain controversial<ref>{{cite journal | authorlink= Lorenzo Iorio| author = Iorio L. | title = Conservative evaluation of the uncertainty in the LAGEOS-LAGEOS II Lense-Thirring test | journal = Central European Journal of Physics | year = 2009 |doi= 10.2478/s11534-009-0060-6}}</ref> (See the voice [[frame-dragging]] for further details). The same effect may have been detected in the data of the [[Mars Global Surveyor]] (MGS) spacecraft<ref>{{cite journal | authorlink= Lorenzo Iorio| author = Iorio L. | title = COMMENTS, REPLIES AND NOTES: A note on the evidence of the gravitomagnetic field of Mars | year = 2006 | journal = Classical Quantum Gravity | volume = 23| issue = 17| pages = 5451-5454 | doi = 10.1088/0264-9381/23/17/N01 }}</ref>, a former probe in orbit around [[Mars]]; also such a test raised a debate<ref>{{cite journal | author = Krogh K. | title = Comment on 'Evidence of the gravitomagnetic field of Mars' | year = 2007 | journal = Classical Quantum Gravity | volume = 24 | issue = 22| pages = 5709-5715 | doi = 10.1088/0264-9381/24/22/N01 }}</ref><ref>{{cite journal | authorlink= Lorenzo Iorio| author = Iorio L. | title = On the Lense-Thirring test with the Mars Global Surveyor in the gravitational field of Mars| journal = Central European Journal of Physics | year = 2009 | url= http://arxiv.org/abs/gr-qc/0701146}}</ref>. First attempts to detect the [[Sun]]'s [[Lense-Thirring]] effect on the [[perihelia]] of the inner [[planets]] have been recently reported<ref>{{cite journal | authorlink= Lorenzo Iorio| author = Iorio L. | title = Advances in the Measurement of the Lense-Thirring Effect with Planetary Motions in the Field of the Sun| journal = Scholarly Research Exchange | volume = 2008 | id = 105235| year = 2008 | doi = 10.3814/2008/105235}}</ref> as well.

==Strong field tests==
{{Main|Binary pulsar}}

[[Pulsars]] are rapidly rotating [[neutron star]]s which emit regular radio pulses as they rotate. As such they act as clocks which allow very precise monitoring of their orbital motions. Observations of pulsars in orbit around other stars have all demonstrated substantial [[periapsis]] precessions that cannot be accounted for classically but can be accounted for by using general relativity. For example, the Hulse-Taylor [[binary pulsar]] [[PSR B1913+16]] (a pair of neutron stars in which one is detected as a pulsar) has an observed precession of over 4o of arc per year. This precession has been used to compute the masses of the components.

Similarly to the way in which atoms and molecules emit electromagnetic radiation, a gravitating mass that is in [[quadrupole]] type or higher order vibration, or is asymmetric and in rotation, can emit gravitational waves.<ref>In general relativity, a perfectly spherical star (in vacuum) that expands or contracts while remaining perfectly spherical ''cannot'' emit any gravitational waves (similar to the lack of e/m radiation from a pulsating charge), as [[Birkhoff's theorem (relativity)|Birkhoff's theorem]] says that the geometry remains the same exterior to the star. More generally, a rotating system will only emit gravitational waves if it lacks the axial symmetry with respect to the axis of rotation.</ref> These [[gravitational waves]] are predicted to travel at the [[speed of light]]. For example, planets orbiting the Sun constantly lose energy via gravitational radiation, but this effect is so small that it is unlikely it will be observed in the near future (Earth radiates about 200 watts (see [[gravitational waves]]) of gravitational radiation). Gravitational waves have been indirectly detected from the Hulse-Taylor binary. Precise timing of the pulses show that the stars orbit only approximately according to [[Kepler's Laws]], – over time they gradually spiral towards each other, demonstrating an [[energy]] loss in close agreement with the predicted energy radiated by gravitational waves. Thus, although the waves have not been directly measured, their effect seems necessary to explain the orbits. For this work [[Russell Alan Hulse|Hulse]] and [[Joseph Hooton Taylor, Jr.|Taylor]] won the [[Nobel prize]].

A "double pulsar" discovered in 2003, J0737−3039, has a perihelion precession of 16.90o per year; unlike the Hulse-Taylor binary, both neutron stars are detected as pulsars, allowing precision timing of both members of the system. Due to this, the tight orbit, the fact that the system is almost edge-on, and the very low transverse velocity of the system as seen from Earth, J0737−3039 provides by far the best system for strong-field tests of general relativity known so far. Several distinct relativistic effects are observed, including orbital decay as in the Hulse-Taylor system. After observing the system for two and a half years, four independent tests of general relativity were possible, the most precise (the Shapiro delay) confirming the general relativity prediction within 0.05%.<ref>{{cite journal | author = Kramer, M. et al. | title = Tests of general relativity from timing the double pulsar | journal = Science |volume = 314 | year = 2006 | pages = 97–102 | doi = 10.1126/science.1132305 | pmid = 16973838}}</ref>

==Gravitational waves==

A number of [[gravitational wave detector]]s have been built, with the intent of directly detecting the [[gravitational wave]]s emanating from such astronomical events as the merger of two [[neutron star]]s. Currently, the most sensitive of these is the [[LIGO|Laser Interferometer Gravitational-wave Observatory (LIGO)]], which has been in operation since 2002. So far, there has not been a single detection event by any of the existing detectors. Future detectors are being developed or planned, which will greatly improve the sensitivity of these experiments, such as the Advanced LIGO detector being built for the LIGO facilities, and the proposed [[LISA (astronomy)|Laser Interferometer Space Antenna (LISA)]]. It is anticipated, for example, that Advanced LIGO will detect events possibly as often as daily.

If gravitational waves exist as predicted, they should be detected by these gravitational wave detectors. Finding or falsifying the existence of gravitational waves as predicted by general relativity is a critical test of the validity of the theory.

==Cosmological tests==
Tests of general relativity on the largest scales are not nearly so stringent as solar system tests.<ref>{{cite paper | author = Peebles, P. J. E.| authorlink = | date= December 2004| title=Testing general relativity on the scales of cosmology| url= http://arxiv.org/abs/astro-ph/0410284 | accessdate= 2006-09-27}}</ref> The earliest such test was prediction and discovery of the [[expansion of the universe]].<ref name=Rudnicki28/> In 1922 [[Alexander Friedmann]] found that Einstein equations have non-stationary solutions (even in the presence of the [[cosmological constant]]).<ref name=Pauli1/><ref>[[#Kragh|Kragh]], 2003, p. 152</ref> In 1927 [[Georges Lemaître]] showed that static solutions of the Einstein equations, which are possible in the presence of the cosmological constant, are unstable, and therefore the static universe envisioned by Einstein could not exist (it must either expand or contract).<ref name=Pauli1>[[#Pauli|W.Pauli]], 1958, pp.219–220</ref> Lemaître made an explicit prediction that the universe should expand.<ref name="Kragh, 2003, p. 153">[[#Kragh|Kragh]], 2003, p. 153</ref> He also derived a redshift-distance relationship, which is now known as the [[Hubble Law]].<ref name="Kragh, 2003, p. 153"/> Later, in 1931, Einstein himself agreed with the results of Friedmann and Lemaître.<ref name=Pauli1/> The expansion of the universe discovered by [[Edwin Hubble]] in 1929<ref name=Pauli1/> was then considered by many (and continues to be considered by some now) as a direct confirmation of the general relativity.<ref>[[#Rudnicki|Rudnicki]], 1991, p. 28</ref> In the 1930s, largely due to the work of [[E. A. Milne]], it was realised that the linear relationship between redshift and distance derives from the general assumption of uniformity and isotropy rather than specifically from general relativity.<ref name=Rudnicki28>[[#Rudnicki|Rudnicki]], 1991, p. 28. ''The Hubble Law was viewed by many as an observational confirmation of General Relativity in the early years''</ref> However the prediction of a non-static universe was non-trivial, indeed dramatic, and primarily motivated by general relativity.<ref>[[#Chandrasekhar|Chandrasekhar]], 1980, p. 37</ref>

Some other cosmological tests include searches for primordial gravity waves generated during [[cosmic inflation]], which may be detected in the [[cosmic microwave background]] [[polarization]] or by a proposed space-based gravity wave interferometer called [[Big Bang Observer]]. Other tests at high redshift are constraints on other theories of gravity, and the variation of the gravitational constant since [[big bang nucleosynthesis]] (it varied by no more than 40% since then).

Some physicists think [[dark energy]] is perhaps due to the effect of living on a [[brane cosmology|brane]],<ref>{{cite journal | last= Dvali| first= G. | coauthors = G. Gabadadze and M. Porrati| authorlink = | year= 2000| title=4-D gravity on a brane in 5-D Minkowski space| journal=Physics Letters| volume = B485 | issue = | pages=208–214 | url= http://arxiv.org/abs/hep-th/0005016| doi = | accessdate= 2006-09-24| format=abstract}}</ref> or due to other corrections to the [[Einstein field equations]].

==References==
===Notes===

{{reflist|2}}

===Other research papers===

* B. Bertotti, L. Iess and P. Tortora, "A test of general relativity using radio links with the Cassini spacecraft", ''Nature'' '''425''', 374 (2003).
* S. Kopeikin, A. Polnarev, G. Schaefer and I. Vlasov, "Gravimagnetic effect of the barycentric motion of the Sun and determination of the post-Newtonian parameter γ in the Cassini experiment", ''Physics Letters A'' '''367''', 276 (2007) [http://adsabs.harvard.edu/abs/2007PhLA..367..276K]
* C. Brans and R. H. Dicke, "Mach's principle and a relativistic theory of gravitation", ''Phys. Rev.'' '''124''', 925-35 (1961).
* A. Einstein, "Über das Relativitätsprinzip und die aus demselben gezogene Folgerungen," ''Jahrbuch der Radioaktivitaet und Elektronik'' '''4''' (1907); translated "On the relativity principle and the conclusions drawn from it," in ''The collected papers of Albert Einstein. Vol. 2 : The Swiss years: writings, 1900–1909'' (Princeton University Press, Princeton, NJ, 1989), Anna Beck translator. Einstein proposes the gravitational redshift of light in this paper, discussed online at [http://www1.kcn.ne.jp/~h-uchii/gen.GR.html The Genesis of General Relativity].
* A. Einstein, "Über den Einfluß der Schwerkraft auf die Ausbreitung des Lichtes," ''Annalen der Physik'' '''35''' (1911); translated "On the Influence of Gravitation on the Propagation of Light" in ''The collected papers of Albert Einstein. Vol. 3 : The Swiss years: writings, 1909–1911'' (Princeton University Press, Princeton, NJ, 1994), Anna Beck translator, and in ''The Principle of Relativity,'' (Dover, 1924), pp 99–108, W. Perrett and G. B. Jeffery translators, ISBN 0-486-60081-5. The deflection of light by the sun is predicted from the principle of equivalence. Einstein's result is half the full value found using the general theory of relativity.
*{{cite journal | last = Shapiro | first = S. S. | authorlink = | coauthors = Davis, J. L.;Lebach, D. E.; Gregory J.S. | title = Measurement of the solar gravitational deflection of radio waves using geodetic very-long-baseline interferometry data, 1979–1999 | journal = Physical Review Letters | volume = 92 | issue = 121101 | page = 121101| publisher = American Physical Society | date = [[26 March]] [[2004]] | url = http://link.aps.org/abstract/PRL/v92/e121101 | doi = 10.1103/PhysRevLett.92.121101 | accessdate = 2007-01-18 | format = abstract }}
* M. Froeschlé, F. Mignard and F. Arenou, "[http://www.rssd.esa.int/Hipparcos/venice-proc/poster01_03.pdf Determination of the PPN parameter γ with the Hipparcos data]" Hipparcos Venice '97, ESA-SP-402 (1997).
* {{cite web | author=Will, Clifford M. | title=Was Einstein Right? Testing Relativity at the Centenary | work=arXiv eprint server | url=http://www.arxiv.org/abs/gr-qc/0504086 | accessdate=August 8, 2005 }}
* {{cite journal|last=Rudnicki|first=Conrad|title=What are the Empirical Bases of the Hubble Law|year=1991|journal=Apeiron|issues=9–10|pages=27–36|url=http://redshift.vif.com/JournalFiles/Pre2001/V0N09PDF/V0N09RUD.pdf|format=PDF|accessdate=2009-06-23}}
* {{cite journal|last=Chandrasekhar|first=S.|title=The Role of General Relativity in Astronomy: Retrospect and Prospect|year=1980|journal=J. Astrophys. Astr.|volume=1|pages=33–45|url=http://www.ias.ac.in/jarch/jaa/1/33-45.pdf|format=PDF|doi=10.1007/BF02727948|accessdate=2009-06-23}}
* {{cite journal|last=Kragh|first=Helge|coauthors=Smith, Robert W.|title=Who discovered the expanding universe|year=2003|volume=41|pages=141–62|journal=History of Science|url=http://www.shpltd.co.uk/kragh-universe.pdf|format=PDF|accessdate=2009-06-23}}

===Textbooks===
* S. M. Carroll, ''Spacetime and geometry: an introduction to general relativity'', Addison-Wesley, 2003 [http://pancake.uchicago.edu/~carroll/grbook/]. An introductory general relativity textbook.
* A. S. Eddington, ''Space, Time and Gravitation'', Cambridge University Press, 1987 (originally published 1920).
* A. Gefter, "Putting Einstein to the Test", ''Sky and Telescope'' July 2005, p. 38. A popular discussion of tests of general relativity.
* H. Ohanian and R. Ruffini, ''Gravitation and Spacetime, 2nd Edition'' Norton, New York, 1994, ISBN 0-393-96501-5. A general relativity textbook.
* {{cite book|last=Pauli|first=Wolfgang Ernst|title=Theory of Relativity|year=1958|isbn=9780486641522|publisher=Courier Dover Publications|chapter=Part IV. General Theory of Relativity}}
* C. M. Will, ''Theory and experiment in gravitational physics'', Cambridge University Press, Cambridge (1993). A standard technical reference.
* C. M. Will, ''Was Einstein Right?: Putting General Relativity to the Test,'' Basic Books (1993). This is a popular account of tests of general relativity.
* [[L. Iorio]], ''The Measurement of Gravitomagnetism: A Challenging Enterprise,'' NOVA Science, Hauppauge (2007). It describes various theoretical and experimental/observational aspects of frame-dragging.

===Living Reviews papers===
* N. Ashby, [http://relativity.livingreviews.org/Articles/lrr-2003-1/ "Relativity in the Global Positioning System"], ''Living Reviews in Relativity'' (2003).
* C. M. Will, [http://www.livingreviews.org/lrr-2006-3 The Confrontation between General Relativity and Experiment], ''Living Reviews in Relativity'' (2006). An online, technical review, covering much of the material in ''Theory and experiment in gravitational physics.'' It is less comprehensive but more up to date.

==External links==
* [http://www2.corepower.com:8080/~relfaq/experiments.html the USENET Relativity FAQ experiments page]
* [http://www.mathpages.com/rr/s6-02/6-02.htm Mathpages article on Mercury's perihelion shift] (for amount of observed GR shift).




{{DEFAULTSORT:Tests Of General Relativity}}
[[Category:Tests of general relativity| ]]
[[Category:Mercury]]

[[es:Pruebas de la relatividad general]]
[[fr:Tests expérimentaux de la relativité générale]]
[[pt:Deflexão da luz]]
[[zh:广义相对论的实验验证]]

Kolonialarchitektur in Nordamerika

2008-05-06T19:30:16Z

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[[Image:Saltbox Concord 2.jpg|thumb|250px|A classic [[Saltbox]], a prime example of colonial architecture.]]
'''American colonial architecture''', also called [[Georgian architecture|Colonial Georgian]], characterizes the style of [[domestic architecture]], church buildings and some institutional and government buildings that were built in America from the earliest colonies until the [[Neoclassical architecture|Neoclassical architectural style]] locally called "Federal" replaced in for high-style buildings in the 1780s.

High-style houses were built by wealthy Anglo Americans in several distinctively local styles, in [[New England]], the mid-Atlantic colonies and the Southern colonies. The American colonial style drew its influence from the Georgian architecture of Great Britain, with indirect sources in [[Italian Renaissance]] style of the sixteenth century. Emigrating craftsmen training in English building practice and a series of printed builders' guides with engraved illustrations both made their contribution to the building vocabulary that spread to the English colonies.

The term ''colonial architecture'' also includes vernacular structures of less refined design.

==Characteristics==
[[Image:Gingerbread House Essex CT.jpg|thumb|right|200px|''"Gingerbread House", buit 1855. A blend of Colonial and early-Victorian architecture'']]
The defining characteristics of [[Georgian architecture]] are its square, symmetrical shape, central door, and straight lines of windows on the first and second floor. There is usually a decorative crown above the door and flattened columns to either side of it. The door leads to an entryway with stairway and hall aligned along the center of the house. All rooms branch off of these. Georgian buildings, in the English manner were ideally in brick, with wood trim, wooden columns and entablatures painted white. In the US, one found both brick buildings as well as those in wood with clapboards. They were usually painted white, though sometimes a pale yellow. This differentiated them from most other structures that were usually not painted.

A Colonial-style house usually has a formally-defined [[living room]], [[dining room]] and sometimes a [[family room]]. The [[bedroom]]s are typically on the second floor. They also have one or two chimneys that can be very large.

==See also==
* [[Colonial Revival]]
* "[[Colonial House]]", a short-run [[television series]] produced by Thirteen/[[WNET]] New York and Wall to Wall Television in the United Kingdom, which aired on [[PBS]] in [[2004]].

==External links==
===Architecture===
*iDesignTalk.com - [http://www.idesigntalk.com Interior Design & Architecture Forums/Community]
*[http://architecture.about.com/library/bl-georgiancolonial.htm About: Colonial Houses]
*[http://images.google.com/images?q=houses%20of%20colonial%20williamsburg&hl=en&lr=&safe=off&sa=N&tab=wi Examples of Colonial House style at Colonial Williamsburg, Virginia]
*[http://www.enonhall.com The Restoration of a Colonial House in Virginia]
===PBS TV Show===
* [http://www.pbs.org/wnet/colonialhouse/ Colonial House PBS series.]
{{arch-style-stub}}

[[Category:House styles]]
[[Category:American architectural styles]]

[[de:Kolonialstil]]

Deodand

2006-08-30T18:36:19Z

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'''Deodand''' is a thing forfeited or given to God, specifically, in law, an object or instrument which becomes forfeit because it has caused a person's [[death]]. In [[medieval Europe]] the object (or its equivalent value) was to pass directly to the church, or else to the Crown, ostensibly to be put to pious use. The word comes from the [[Latin]] ''Deo dandum'' which means to be given to [[God]].

Because the item forefeit to the Crown could be assigned a monetary value, courts tended to pay more attention to this value - which would accrue to the authorities - than to the crime or accident in which it featured, or to the victim who suffered the consequences. Until 1846 in the [[United Kingdom]], the proceeds of selling the item might be used as compensation for the relatives of the victim.

On Christmas Eve [[1841]] in an accident on the [[Great Western Railway]] a train ran into a [[landslip]] in [[Sonning Cutting]] and eight passengers were killed; the inquest jury assigned a deodand value of £1000 to the train. The Board of Trade inspector exonerated the Company from blame, and the damages were reduced to a nominal sum. The case highlighted the problems of applying medieval law to the developing commercial society, and forfeiture of deodands was abolished in the UK by the Fatal Accidents Act of 1846 (usually referred to as [[Lord Campbell's Act]]).

Some [[State constitution (United States)|U.S. state constitutions]] ban deodands, frequently in the same article that bans [[corruption of blood]].

== Other uses ==

There is also a creature called the Deodand which appears repeatedly in [[Jack Vance]]'s popular [[Dying Earth]] series. It is carnivorous, malicious, and sentient, and is described by Vance as "formed and featured like a handsome man, finely muscled, but with a dead black lusterless skin and long slit eyes". Within the books the wizard Follinense, in "his bizarre systemology," classifies it as a hybrid of "wolverine, basilisk, man."

[[Category:Latin legal phrases]]

Beverston Castle

2006-08-21T14:39:55Z

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[[Image:Beverston_castle.jpg|thumb|210px|Beverston Castle south tower of western range]]

'''Beverston Castle''' was originally constructed as a [[medieval]] stone [[fortress]] and is situated in the village of Beverston, [[Gloucestershire]], [[England]]. The [[castle]], also known as '''Beverstone Castle''', was founded in AD 1229 by [[Maurice de Gaunt]]. Much of the castle is presently in the state of ruin [[as of 2006]], but a portion of the structure is occupied, and an expansive handsome garden is part of the estate. The castle is situated in the centre of [[Beverston]] village, approximately 200 meters north (and out of sight) of the A4135 highway transecting Beverston.

The original castle design was in an approximately pentagonal form; later in the early 14th century, a small quadrangular stronghold was added along with a twin towered [[gatehouse]]. Beverston Castle is situated approximately three kilometres west of the town of [[Tetbury]] and about two kilometers east of the medieval [[abbey]] annex, [[Calcot Manor]]. The castle is situated in the [[Cotswolds]], a designated [[Area of Outstanding Natural Beauty]] (AONB), which is an area of countryside with significant landscape value in [[England]], [[Wales]] or [[Northern Ireland]], that has been specially designated by the [[Countryside Agency]] on behalf of the [[United Kingdom government]]

==History==

[[Image:Beverston gatehouse.jpg|thumb|220px|left|Beverston Castle gatehouse viewed from the inside]]

Early [[Roman]] remains have been found in the near vicinity at [[Calcot Manor]], indicating habitation of this area as early as 400 AD<ref>C.Michael Hogan. ''History and Architecture of Calcot Manor'', prepared for Calcot Manor, Lumina Press, Aberdeen, July 5, 2006</ref>, although it is likely that earlier [[Iron Age]] peoples would have also been in this locale. Historically in medieval times the site is known as Beverstone, but in the earlier [[Middle Ages]] it was called Beverstane. Another early label for this site was Bureston, derived from the large number of blue stones found here<ref>''Gloucestershire Notes and Queries, Volume 5'', Edited by W.P.W. Phillimore, M.A., B.C.L., first published in 1894</ref>.
.
The site itself is known to have been the location of an important circa 1140 AD battle between the opposing English armies of [[King Stephen]] and [[Empress Matilda]][http://homepage.mac.com/philipdavis/Indexs/EngCounty/Gloucestershire.html]. Apparently Maurice de Gaunt constructed the original castle somewhat prior to [[1229]] AD without a royal licence, but was granted a licence for the purpose of adding [[crenellation]]. This early castle was fortified by a T-shaped ditch, part of which is still intact in the appearance of a partial [[moat]] on the south side of the castle. In the early 14th century, [[Thomas, Lord Berkeley]], the rich (1293-1361), modified Beverston Castle, erecting a small quadrangular [[stronghold]], with a twin-towered [[gatehouse]]. A smaller square tower was added in the late 15th century.

In the 16th century, it is known that Sir Michael Hicks (son of from London and Julia Arthur) owned Beverston Castle and passed the Beverston holding to his son Sir William Hicks, 1st Bart of Beverston. The estate remained in the Hicks family through at least the early 19th century.. From military outfall of the Civil War (mid-seventeenth century), much of Beverston Castle was destroyed<ref>''House of Commons Journal Volume 4'', London, 28 July, 1646</ref>. Roundhead forces attacked the castle twice during the Civil War, but the greatest blow may have been an order from Parliament to dismantle its defensive works. The western and southern ranges along with the gatehouse with one of its original D-shaped towers have survived.

==Architecture==

The massive extant west range of Beverston Castle (ST862-940) is flanked on its angles with square towers, and it contains a [[solar (room)|solar]] above a vaulted [[undercroft]]. The pentagon shaped [[masonry]] castle has two surviving, albeit ruined, round towers from the original 13th century construction of de Gaunt. The dressed bluish [[limestone]] appears to be of the same [[quarry]] source as nearby Calcot Manor. The two storey gatehouse, with one extant D-shaped tower, was added by Lord Berkeley in the 1350-1360 era. The gatehouse [[arch]], totally intact as of 2006, would have originally been protected by an immense [[portcullis]]. Above the archway was a sizable first floor (second story in American vernacular) [[chamber]]. The ruined northwest square tower dates to the 14th century (Lord Berkeley’s work) further modified in the late 15th century.

The southern domestic range, occupied as of 2006, was built by the Hicks family in the early 17th century, reflecting an age of growing security for large manor houses. This range was originally occupied by a medieval [[great hall]] from either the de Gaunt or Berkeley era. In the year 1691 a fire damaged this southern range, which was restored soon thereafter.

[[Image:Beverstoncastlegarden.JPG|thumb|210px|Garden at Beverston Castle looking south]]

==Present aspect==

As of the year 2006, Beverston Castle is in private ownership. Some good photographs can be acquired from the public road providing access to the castle. The ancient moat has been incorporated into the expansive and well cared for [[garden]]. The gardens are considered a good site for viewing wild [[orchid]]s<ref>Lorna Parker, ''Seasonal Guide to Gardens and Nature Preserves in the Cotswalds'', The Cotswalds Review, 2006</ref>. The southern entrance to the castle is by way of a bridge over the vestigial moat. Vehicle access to the north side of the castle is through the ancient gatehouse arch.

==See also==
*[[Calcot Manor]]
*[[Oliver Cromwell]]

== References==
<div style="font-size:90%;">
<references />
</div>

==External links==
*[http://homepage.mac.com/philipdavis/Indexs/EngCounty/Gloucestershire.html Fortified Castles of Gloucestershire]
*[http://www.glosgen.co.uk/tetbury.htm View of Tetbury area in the 18th century]

[[Category:Buildings and structures in Gloucestershire]]
[[Category:Castles in England]]
[[Category:English Heritage]]
[[Category:History of Gloucestershire]]

Luftangriff auf Darwin

2006-02-19T06:07:28Z

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{{Infobox Military Conflict
|conflict=Air raids on Darwin, February 1942
|image=[[Image:Darwin_42.jpg|300px]]
|caption= The explosion of an oil storage tank, hit during the first Japanese air raid on Darwin, February 19, 1942. In the foreground is [[HMAS Deloraine|HMAS ''Deloraine'']], which escaped damage.
|partof=[[World War II]], [[Pacific War]]
|date=[[February 19]] [[1942]]
|place=[[Darwin, Australia]]
|result=Japanese victory
|combatant1=[[Australia]]; [[United States]]
|combatant2=[[Japan]]
|commander1=[[David Valentine Jardine Blake|David V. J. Blake]]
|commander2=[[Chuichi Nagumo]]
|strength1=30 planes
|strength2=242 planes
|casualties1=At least 243 killed; (possibly 1,100 dead in total) 20 planes destroyed 10 ships sunk
|casualties2=One killed; ? missing; six taken prisoner. Four planes destroyed in Australian airspace; ? failed to return.
|}}
{{Campaignbox Pacific 1941}}

The two '''[[Japan]]ese air raids on [[Darwin, Australia]]''', on [[February 19]], [[1942]] were by far the biggest ever attack by a foreign power against the [[Australia|Australian mainland]]. They were also a significant action in the [[Pacific War|Pacific campaign]] of [[World War II]] and represented a major psychological blow to the Australian population, several weeks after hostilities with Japan had begun. The raids were the first of about 100 '''[[Japanese air attacks on Australia, 1942-43|air raids against Australia]]''' during 1942-43.

Darwin, which in 1942 had a population of about 2,000 — the normal civilian population of about 5,000 had been reduced by evacuation — was a strategically-placed naval port and airbase, and there were about 15,000 Allied soldiers in the area. Although it was a relatively less significant target, a greater number of bombs were dropped than in the [[attack on Pearl Harbor]]. Darwin was unprepared, and although it came under attack from the air another 63 times in 1942 and 1943, these first two raids were massive and devastating by comparison.

==The forces==
Most of the attacking planes came from the four [[aircraft carrier]]s of the [[Imperial Japanese Navy]]'s Carrier Division 1 ([[Japanese aircraft carrier Akagi|''Akagi'']] and [[Japanese aircraft carrier Kaga|''Kaga'']]) and Carrier Division 2 ([[Japanese aircraft carrier Hiryu|''Hiryu'']] and [[Japanese aircraft carrier Soryu|''Soryu'']]), commanded by Admiral [[Chuichi Nagumo]]. Land-based [[heavy bomber]]s were also involved. The Japanese launched two waves of planes, comprising 242 [[bomber]]s and [[fighter]]s.

Darwin was relatively well covered by anti-aircraft fire. However, the only operational [[Royal Australian Air Force]] (RAAF) fighter squadrons were in [[Europe]], [[North Africa]] or the [[Middle East]]; the only modern fighters based in Darwin were 11 [[P-40]]s from the [[United States Army Air Force|US Army Air Force]]'s 33rd Pursuit Squadron, in addition to lightly armed and/or obsolescent training and patrol aircraft belonging to the RAAF. An experimental [[radar]] station was not yet operational.

==The attacks==
The first wave of 188 Japanese planes, led by naval Commander [[Mitsuo Fuchida]] took off at 8.45am. At about 9.15am, it was spotted by civilians on [[Bathurst Island|Bathurst]] and [[Melville Island]]s, and Darwin was warned at least twice by radio, no later than 9.35. However, the warnings were not taken seriously, and the attackers arrived at their target just before 10.00am.

Fuchida later wrote of the raid:
:''[T]he job to be done seemed hardly worthy of the Nagumo Force. The harbour, it is true, was crowded with all kinds of ships, but a single pier and a few waterfront buildings appeared to be the only port installations. The airfield on the outskirts of the town, though fairly large, had no more than two or three small hangars, and in all there were only twenty-odd planes of various types scattered about the field. No planes were in the air. A few attempted to take off as we came over but were quickly shot down, and the rest were destroyed where they stood. Anti-aircraft fire was intense but largely ineffectual, and we quickly accomplished our objectives.''

In fact, the Japanese encountered five of the USAAF P-40s, which had recently returned from an aborted mission over [[Timor]] and were still carrying [[drop tank]]s — with both numbers and surprise on their side, Japanese fighters shot down all of the US planes, except one piloted by Lt Robert Ostreicher.

A total of 71 [[Nakajima B5N]] "Kate" torpedo bombers then attacked shipping — at least 45 vessels — in the harbour, while 81 [[Aichi D3A]] "Val" dive-bombers, escorted by 36 [[Mitsubishi A6M]] Zero fighter planes attacked [[Royal Australian Air Force]] (RAAF) bases, civil airfields, and a hospital. Ostreicher shot down two Vals, and managed to survive the attack, but no Allied planes successfully took off, and all were destroyed or rendered unable to fly after the first attack. By about 10.40 the first wave of Japanese planes had left the area.

Just before midday, there was a high altitude attack by land-based bombers, concentrated on the [[RAAF Base Darwin|Darwin RAAF Airfield]]: 27 [[Mitsubishi G3M]] "Nell" bombers flew from [[Ambon]] and 27 [[Mitsubishi G4M]] "Betty" from [[Kendari]], [[Sulawesi]]. This second raid lasted for 20-25 minutes.

In spite of Fuchida's assessment of the anti-aircaft fire as "largely ineffectual", the lack of armour and self-sealing fuel tanks in many Japanese planes, as well as the prolonged low-level [[strafe|strafing]] runs carried out, made pilots and planes exceptionally vulnerable to ground fire. Most Australian sources say that four Japanese planes were destroyed in Australian airspace; it has been suggested that several more failed to return to their carriers or bases.

==Casualties, damage and consequences==
At least 243 civilians and military personnel were killed, most of them on the sunken ships — it has been argued that the real toll was much higher: for instance, anecdotal accounts report 300 bodies being buried in a mass grave at a beach.[http://www.schools.nt.edu.au/ths-wwII/stats.html] Authorities probably did not take stock of the impact on the numerically significant [[indigenous Australian]] population of the area. A secret military intelligence report estimated the casualties at 1,100, equal to about half the number killed at Pearl Harbor. At least 330 people were wounded and 200 of these were seriously injured. The total number of these people who died from their wounds was not recorded.

The air raids caused chaos in Darwin. Most of the essential services were destroyed. Fear of an imminent invasion spread and there was a wave of refugees, as half of the town's civilian population fled. There were reports of looting and in some cases — it was alleged — the culprits were [[Provost Marshal]]s. Many civilian refugees never returned, or did not return for many years, and in the post-war years some claimed that land they owned in Darwin had been usurped by government bodies in their absence.

According to official figures, 278 servicemen were considered to have [[desertion|deserted]] as a result of the raids, although it has been argued that the "desertions" mostly resulted from ambiguous orders given to RAAF ground staff during the attack.

Eight ships were sunk in Darwin Harbour: the [[United States Navy]] [[destroyer]] [[USS Peary (DD-226)|USS ''Peary'']], the large [[United States Army|US Army]] transport ship ''[[USAT Meigs]]'', the Australian [[patrol boat]] [[HMAS Mavie|HMAS ''Mavie'']] and the [[merchant ship]]s ''British Motorist'', ''Kelat'', ''Mauna Loa'', ''[[Neptuna]]'', and ''Zealandia''.

The USAAF lost 10 P-40s, one [[B-24]] bomber, and three [[C-45]] transport planes. The US Navy lost three [[PBY Catalina]] flying boats. The RAAF lost six [[Lockheed Hudson]]s.

The success of the Darwin raid led to calls within the Japanese Navy for an invasion of Australia. Admiral [[Osami Nagano]], the Chief of the Navy General Staff, was in favour. But the [[Imperial Japanese Army]] lacked the troops for such an undertaking and Admiral [[Isoroku Yamamoto]]'s plan for an [[battle of Midway|attack on Midway Island]] was preferred.

The [[Allied]] navies largely abandoned the naval base at Darwin after the attack, dispersing most of their forces to [[Brisbane]], [[Fremantle]] and smaller ports. Conversely, Allied air commanders launched a major build-up in the Darwin area, building more airfields and deploying many squadrons.

== See also ==

* [[Japanese air attacks on Australia, 1942-43]]
* [[Christmas Island Invasion]]
* [[Planned invasion of Australia during World War II]]
* [[Military_history_of_Australia#Second_World_War_1939-1945|Military history of Australia during World War II]]
* [[Military_history_of_Japan#Showa_Period_-_World_War_II|Military history of Japan during World War II]]

==References==
* Mitsuo Fuchida and M. Okumiya, ''Midway: the Battle that doomed Japan'', Hutchinson, 1957.

==External links==
*[http://home.st.net.au/~dunn/darwin02.htm Peter Dunn's AUSTRALIA @ WAR, 2004, "Two Japanese Air Raids at Darwin, NT on 19 February 1942" ]
*[http://www.netherlandsnavy.nl/Special_darwin.htm Tom Womack, 2005, "Australia's Pearl Harbor: the Japanese air raid on Darwin"]
*[http://www.naa.gov.au/Publications/fact_sheets/fs195.html National Archives of Australia, 2000, "Fact Sheet 195 The bombing of Darwin" ]
*[http://www.users.bigpond.com/battleforaustralia/battaust/CharlieUnmack.html "A Darwin Eyewitness Account – Stoker 2nd Class Charlie Unmack" ]
*[http://www.users.bigpond.com/battleforaustralia/battaust/LACHawker.html "A Darwin Eyewitness Account – Leading Aircraftman Stanley Hawker, No 2 RAAF Squadron." ]

[http://www.schools.nt.edu.au/ths-wwII/index2.html Taminmin High School, "Defending the Darwin Fortress" ]

{{WWII city bombing}}

[[Category:1942]]
[[Category:Darwin]]
[[Category:History of Australia]]
[[Category:World War II aerial operations and battles of the South Pacific Campaign]]
[[pt:Ataques aéreos a Darwin]]
[[de:Bombenangriff auf Darwin]]