Dokaz! - Gravitacija in svetloba imata enako hitrost

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Dokaz! - Gravitacija in svetloba imata enako hitrost

Odgovor Napisal/-a Viola » 10.1.2003 11:01

No sedaj so tudi dokazali, da se gravitacija širi s svetlobno hitrostjo!
Merili so svetlobo nekega objekta za Jupitrom in tako prišli do zaključka, da se gravitacija širi s hitrostjo 0,95c +/- 0,25!

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Odgovor Napisal/-a zupan » 10.1.2003 11:56

Zanimivo. Morda ves natancneje, kje je bilo to objavljeno?

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Gravitacija in svetloba imata enako hitrost!

Odgovor Napisal/-a saso » 10.1.2003 18:34

Gravity and light move at the same speed
8 January 2003

Scientists have succeeded in measuring the speed of gravity for the first time. Sergei Kopeiken of the University of Missouri-Columbia and Ed Fomalont of the National Radio Astronomy Observatory in the US used a rare cosmic alignment to check that gravity and light travel at the same speed -- as predicted by Einstein. The astronomers presented their findings today at the American Astronomical Society meeting in Seattle.

On September 8 last year Jupiter passed almost directly between the Earth and the quasar J0842+1835. Kopeikin and Fomalont used the Very Long Baseline Array of radio telescopes in the US and a 100-metre radio telescope in Effelsberg, Germany, to measure how radio waves from the quasar were deflected by Jupiter. Previously they had shown that the size of the deflection depends on the speed at which gravity propagates from Jupiter. From their measurements Kopeikin and Fomalont calculated the speed of gravity to be 95% of the speed of light, with an error margin of plus or minus 25%.

Prior to this work, physicists had assumed that the only way to measure the speed of gravity was to detect gravitational waves. Kopeikin believes that this new result is the first of many observations of gravitation that will shed new light on the general theory of relativity.

http://physicsweb.org/article/news/7/1/2


American Astronomical Society,
Seattle, January 2003

Speed of gravity and light equal
Einstein's theory of general relativity passes quasar test.
8 January 2003
JOHN WHITFIELD


The speed of gravity is the same as that of light, say two physicists.

Knowing the speed of gravity is important for theories that attempt to unify the two pillars of physics: general relativity and quantum mechanics. The gravity measurement is not yet precise enough to rule any ideas in or out, but it confirms what most researchers had thought.

Einstein's theory of relativity only holds if the force of gravity acts at the same speed as light. Until now this was merely an assumption, says theoretical physicist Sergei Kopeikin of the University of Missouri in Columbia.

In 1999, Kopeikin extended Einstein's theory to explain how the gravitational fields of moving bodies distort radio waves and light. The speed of gravity can be calculated from measuring these effects.

The chance to take a reading came on 8 September last year. Jupiter passed in front of a distant quasar called J0842. Quasars are intense sources of radio waves that are thought to be giant black holes at the centres of galaxies.

Jupiter eclipses a quasar about once a decade. The planet's gravity bends the quasar's radio waves, shifting the quasar's apparent position in the sky.

If the speed of gravity were infinite, Kopeikin predicted that the quasar should have traced a perfect circle in the sky as Jupiter passed. If gravity had some finite speed, this circle would distort into an ellipse.

The distortion is tiny - equivalent to spotting a pin 250 miles away. To detect it, Kopeikin and his colleague Edward Fomalont of the US National Radio Astronomy Observatory in Charlottesville, Virginia, used a network of radio telescopes in the United States and Germany.

Groups of telescopes can function like a single huge instrument, through a technique called interferometry. By comparing the differences in the signals received at different places, the team pinpointed the quasar's position with incredible accuracy.

The shape of the quasar's motion gave a speed of gravity nearly identical to that of light, with an error margin of plus or minus 20%. "You can rule out a speed of gravity greater than twice the speed of light with a high degree of confidence," Fomalont told the American Astronomical Society's meeting in Seattle this week.

Subtle deviance

Physicists are looking for small deviations from general relativity, in the hope that it will give them a clue to how it can be reconciled with quantum theory.

For example, if there were more than the four dimensions of space and time that we are familiar with - as some theorists suggest - then gravity might be able to 'speed up' by taking a short cut through them.

Knowing the speed of gravity helps to put limits on these possibilities. But it's too early to draw definite conclusions, says physicist Craig Hogan of the University of Washington in Seattle. "This isn't going to rule out anybody's cherished beliefs."

Other, more precise experiments using different techniques will help to pin down the speed of gravity, says Hogan.


© Nature News Service / Macmillan Magazines Ltd 2002

http://www.nature.com/nsu/030106/030106-8.html

XJam

Odgovor Napisal/-a XJam » 10.2.2003 2:28

Mislim, da to še zdaleč ni dokaz! Je pa Fomalontova in Kopejkinova meritev odlklona radijskih valov kvazarja J0842+1835 z Jupitra eden izmed prvih preskusov, ki o tem odloča na ta način. Spomnimo se meritev enakosti pospeševalne in težnostne mase (Ëtvos, Pekar, Fekete (1922) - relativna napaka meritve 10^{-8}, Roll, Krotkov, Dicke (1964) - relativna napaka 10^{-11}, Braginskij, Panov (1971) - relativna napaka 10^{-12}). Tukaj pa je relativna napaka ± 25*10^{-2}.

Zanimivo je v luči zgornjega preskusa prebrati tudi razvpite argumente nekdanjega astronoma Ameriškega pomorskega observatorija (USNO) Toma Van Flanderna v 'očitno napačnem' članku Hitrost gravitacije - kaj pravi preskus, objavljenem tudi v Phys. Lett. A 250 (1998): 1 -- 11. Eden od vodilnih strokovnjakov gravitacijske fizike Steve Carlip se je odzval na Flandernova 'majava' razmišljanja v članku Aberacija in hitrost gravitacije, Phys. Lett. A 267 (2000) 81-87. Seveda Flandern Carlipovega odziva ni sprejel, in v svojem zadnjem 'napadu' Hitrost gravitacije - preklic hitrostne meje, še vedno trdi, da je po vsej verjetnosti zgornja meja za hitrost gravitacije nekako 2*10^{10} c. Kdo ima potlej prav?

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Re: Dokaz! - Gravitacija in svetloba imata enako hitrost

Odgovor Napisal/-a amrit » 22.1.2009 20:27

transfer energje gravitacije je trenuten

see

http://www.fqxi.org/data/forum-attachme ... __2009.pdf

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shrink
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Re: Dokaz! - Gravitacija in svetloba imata enako hitrost

Odgovor Napisal/-a shrink » 22.1.2009 20:35

amrit napisal/-a:transfer energje gravitacije je trenuten

see

http://www.fqxi.org/data/forum-attachme ... __2009.pdf
Humbug!

Roman
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Re: Dokaz! - Gravitacija in svetloba imata enako hitrost

Odgovor Napisal/-a Roman » 23.1.2009 8:29

amrit napisal/-a:transfer energje gravitacije je trenuten
Točno. To je dokazal že Vladimir Babula v svojem ZF romanu "Planet treh sonc". Prevod smo dobili že leta 1959.

Roman
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Re: Dokaz! - Gravitacija in svetloba imata enako hitrost

Odgovor Napisal/-a Roman » 23.1.2009 9:24

Še nekaj, amrit. Pokukal sem v tvoj članek. Izgleda, da želiš iz kvantne prepletenosti izpeljati nelokalnost gravitacije, ampak tega ne storiš. Nobene povezave, nobene izpeljave, nobene formule, nič. Povsem neuporabna referenca.

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GJ
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Re: Dokaz! - Gravitacija in svetloba imata enako hitrost

Odgovor Napisal/-a GJ » 23.1.2009 9:56

amrit napisal/-a:transfer energje gravitacije je trenuten
Am rit, ti si poosebjena zmedenost, ki hoče ugajati.
Zakaj nisi ostal pri svojem dosedanjem poslu? Mislim pri tehtanju črvjih duš.

Transfer (prenos) energije ne more bit trenuten, saj bi s tem kršil zakon o ohranitvi energije.
No morda pa verjameš v perpetuum mobile, v kar se ne bi (več) čudil. :lol:

Lep dan ti želim pa čeprav si v kriznih letih..

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