Moving objects in retarded gravitational potentials of an expanding spherical shell/Brief historical review

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Brief historical review

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The finiteness of the propagation speed of gravity and its influence to gravitational forces was originally stated by Paul Gerber (1854–1909) in 1898.[1]

Shortly before his early death the German astronomer and physicist Karl Schwarzschild (1873–1916) published a paper on "Über das Gravitationsfeld einer Kugel aus inkompressibler Flüssigkeit nach der Einsteinschen Theorie" (english: "On the gravitational field of a sphere of incompressible fluid according to Einstein's theory"), where he described how to compute the smallest possible radius for a sphere with a given mass. He found the radius for a sphere with the mass of the sun to be three kilometres.[2] In recognition of his achievement, the corresponding radius is now called the Schwarzschild radius.

In 1933 the Swiss astronomer Fritz Zwicky obeserved a gravitational anomaly in the Coma galaxy cluster, and he coined the term dark matter (in German: "dunkle Materie") for the cause of this anomaly.[3]

In 1953 the German astrophysicist Erwin Finlay-Freundlich (1885–1964) derived a blackbody temperature for intergalactic space of 2.3 Kelvin according to his theory of tired light.[4] The German-British mathematician and physicist Max Born (1882–1970) immediately recommended taking the problem seriously and pursuing it further.[5]

Map of cosmic background radiation with artificial colours that show tiny temperature variations.

In 1965 the cosmic microwave background (CMB) was discovered by US-American radio astronomers Arno Allan Penzias (1933–2024) and Robert Woodrow Wilson (born 1936).[6] It has a thermal black body spectrum at a very low temperature of about 2.7 Kelvin. Since the cosmic microwave background was mainly created in the visible area of the electromagnetic spectrum, it must have undergone a strong wavelength extension on its way to the observers. This can happen because of two main reasons:

  • The origin of the radiation moves away from us very quickly, which will cause an increase of the wavelength according to the Doppler effect described by Christian Doppler (1803–1853) in 1842.[7]
  • There is a huge mass behind the origin of the radiation, which will cause an increase of the wavelength according to the gravitation and the relativity principle of Albert Einstein (1879–1955) of 1907.[8]

The redshift factor is defined as a relation between an emitted wavelength and an observed wavelength of electromagnetic radiation:

The redshift of the cosmic microwave background was found to be in 2003, which is an extremely high value.[9] The age of the universe at the time this background radiation was created by hydrogen atoms has been estimated at around 400,000 years.[10] In January 2024 the very young and very far galaxis JADES-GS-z14-0 was found with the Near-Infrared Spectrograph (NIRSpec) the James Webb Space Telescope (JWST). This galaxy was observed in a state 290 million years after the big bang. Its redshift measured with the well-known Lyman alpha break at a wavelength about 1.8 micometres has a very high value of a good 14, which is much lower than that of the cosmic microwave background.[11]

Observations of distant type Ia supernovae published by both the Supernova Cosmology Project as well as the High-Z Supernova Search Team in 1998 show that the relative expansion of the universe is accelerating. For the analysis the astronomers Saul Perlmutter, Brian P. Schmidt and Adam Riess were awarded the Nobel Prize in Physics in 2011.[12]

The evolution of the universe according to the interpretation of the WMAP measurements. The acceleration of the expansion leads to the concave outer rim surface of the evolution cone today.
The contents of of the universe today (top) and 380,000 years after the Big Bang (bottom) according to the interpretation of the WMAP measurements.

From 2001 to 2010 the NASA spacecraft Wilkinson Microwave Anisotropy Probe (WMAP) was investigating the cosmic microwave background. Its measurements led to the current Standard Model of Cosmology. According to this model the universe currently consists of less than 5 percent ordinary baryonic matter; about 24 percent cold dark matter (CDM) that interacts only weakly with ordinary matter and electromagnetic radiation; and more than 70 percent of dark energy that is used to explain the accelerated expansion of the universe.[13] These data were more or less confirmed by the Planck space observatory that was operated by the European Space Agency (ESA) from 2009 to 2013.[14]

In 2013 the Indian researcher Chandrakant Raju proposed to apply the retarded gravitation theory (RGT) to explain the flyby anomaly of spacecrafts in the graviational field of the earth as well as the acceleration of masses in the retarded gravitational fields of spriral galaxies.[15]

In 2016, researchers from the gravitational-wave observatory LIGO reported the first direct measurement of gravitational waves generated by the collision of two black holes (gravitational wave event GW150914).[16] Already in 2017 the Nobel Prize in Physics was awarded for the first direct observation of gravitational waves.[17]

On 17th August 2017 a merging binary neutron star was observed independently and simultanuously by the Advanced LIGO and Virgo detectors (gravitational wave event GW170817) and the Fermi Gamma-ray Burst Monitor as well as the Anticoincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory (gamma ray burst event GRB 170817A).[18] These observations prove that the propagation velocity of gravitational waves must be extremly close to that of electrodynamic waves.

References

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  1. ↑ Gerber, Paul (1898). Mehmke, R.; Cantor, M. (eds.). "Die räumliche und zeitliche Ausbreitung der Gravitation" [The spatial and temporal expansion of gravity]. Zeitschrift für Mathematik und Physik (in German). Leipzig. 43: 93–104 – via Verlag B. G. Teubner.
  2. ↑ Schwarzschild, Karl (1882). Deutsche Akademie der Wissenschaften zu Berlin (ed.). Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften zu Berlin. Smithsonian Libraries. Berlin : Deutsche Akademie der Wissenschaften zu Berlin. pp. 424–434.
  3. ↑ Fritz Zwicky (1933). "Die Rotverschiebung von extragalaktischen Nebeln" [The red shift of extragalactic neubulae]. articles.adsabs.harvard.edu. Retrieved 2024-06-11.
  4. ↑ Finlay-Freundlich, Erwin (1953). "Über die Rotverschiebung der Spektrallinien" [On the redshift of spectral lines]. Nachrichten der Akademie der Wissenschaften in Göttingen. Göttingen: Vandenhoeck & Ruprecht (7): 94–101.
  5. ↑ Born, Max (1953). "Theoretische Bemerkungen zu Freundlichs Formel für die stellare Rotverschiebung" [Theoretical remarks to Freundlich's formula for the stellar redshift]. Nachrichten der Akademie der Wissenschaften in Göttingen. Göttingen: Vandenhoeck & Ruprecht (7): 102–108.
  6. ↑ Penzias, Arno Allan; Wilson, Robert Woodrow (1965). "A Measurement of Excess Antenna Temperature at 4080 Mc/s". The Astrophysical Journal. 142 (1): 419–421. doi:10.1086/148307.
  7. ↑ Doppler, Christian (1842). "Ueber das farbige Licht der Doppelsterne und einiger anderer Gestirne des Himmels" [On the Coloured Light of the Double Stars and some other Celestial Bodies]. Abhandlungen der Böhmischen Gesellschaft der Wissenschaften (5/2): 465–485.
  8. ↑ Einstein, Albert (1907). "Relativitätsprinzip und die aus demselben gezogenen Folgerungen" [On the Relativity Principle and the Conclusions Drawn from It] (PDF). Jahrbuch der Radioaktivität (4): 411–462.
  9. ↑ C. L. Bennett, M. Halpern, G. Hinshaw, N. Jarosik, A. Kogut, M. Limon, S. S. Meyer, L. Page, D. N. Spergel, G. S. Tucker, E. Wollack, E. L. Wright, C. Barnes, M. R. Greason, R. S. Hill, E. Komatsu, M. R. Nolta, N. Odegard, H. V. Peirs, L. Verde, J. L. Weiland (2003). "First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Preliminary Maps and Basic Results". Astrophys. J. Suppl. 148: 1–27. doi:10.1086/377253.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ↑ "Microwave (WMAP) All-Sky Survey | Guide | Digital Universe | Hayden Planetarium". web.archive.org. 2013-02-13. Retrieved 2024-06-01.
  11. ↑ Stefano Carniani, Kevin Hainline (2024-05-30). "NASA's James Webb Space Telescope Finds Most Distant Known Galaxy". webbtelescope.org.
  12. ↑ "The Nobel Prize in Physics 2011". NobelPrize.org. Retrieved 2024-03-16.
  13. ↑ Francis, Matthew (2013-03-21). "First Planck results: the Universe is still weird and interesting". Ars Technica. Retrieved 2024-06-11.
  14. ↑ "ESA Science & Technology - From an almost perfect Universe to the best of both worlds". sci.esa.int. Retrieved 2024-06-11.
  15. ↑ Raju, Chandrakant (2013-11-27). "Retarded gravitation theory" (PDF). Penang, Malaysia: School of Mathematical Sciences, Universiti Sains Malaysia. arXiv:1102.2945. Retrieved 2024-03-22.
  16. ↑ LIGO Scientific Collaboration and Virgo Collaboration; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K. (2016-02-11). "Observation of Gravitational Waves from a Binary Black Hole Merger". Physical Review Letters. 116 (6): 061102. doi:10.1103/PhysRevLett.116.061102.
  17. ↑ "The Nobel Prize in Physics 2017". NobelPrize.org. Retrieved 2024-03-16.
  18. ↑ LIGO Scientific Collaboration; Virgo Collaboration; Monitor, Fermi Gamma-Ray Burst; INTEGRAL (2017-10-20). "Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A". The Astrophysical Journal Letters. 848 (2): L13. doi:10.3847/2041-8213/aa920c. ISSN 2041-8205.
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