A multinational team of astronomers from Spain, Italy and the USA, have found a new Einstein Ring, a rare image of a distant galaxy lensed by gravity. In his seminal general theory of relativity published a century ago, Albert Einstein predicted that gravity would distort the fabric of spacetime, and that light would follow curved paths as a result. Astronomers first observed this effect in 1919, by measuring the position of stars near the Sun during the 1919 total solar eclipse, and noting a slight shift resulting from the gravitational field of our nearest star. On a larger scale, light from distant galaxies is bent by black holes and massive galaxies that lie between them and the Earth. The intervening objects act as lenses, creating arcs and ‘Einstein rings’ of light. These rings are still comparatively rare and usually appear as small features in the sky. This makes them hard to see clearly, and most are observed with radio telescopes, or with the Hubble Space Telescope. The newly discovered ring lies in the direction of the constellation of Sculptor in the southern sky. https://www.ras.org.uk/news-and-press/2843-a-new-einstein-ring
Ignoring our rather tiresome troll friend........Please Register or Log in to view the hidden image! [As per usual of course with his many denials, if he had anything of substance, he would be in line for the Nobel: Instead though, he appears to be in battle for the wooden spoon award.] Please Register or Log in to view the hidden image! Really, there is nothing so awesome, so satisfying, as watching cosmology and the professionals at the coal face, coming up with these incredible results. And to think they were all predicted by Einstein and GR 100 years ago, and some have now just been confirmed is even more staggering. The many millions spent on GP-B and aLIGO were all well worth it and have added staggering knowledge to how the universe/space/time operates. The perhilion shift of Mercury, gravitational time dilation, BH's gravitational lensing, curved spacetime, have all been verified and confirmed beyond any reasonable doubt. Despite the still unanswered questions that remain, 21st century cosmology has laid the groundwork with still more momentous discoveries ahead.
I have no problem with bending of light, I think it is safely confirmed by many observations. What I have been trying to discuss is that I dont think that bending of light can be regarded as direct and specific confirmation of spacetime curvature. Bending of light is simply caused by gravity affecting the photons with effective ("relativistic") mass.
You have been shown at least a couple of reasons why the bending of space is the most logical conclusion from the observations. The other point I suppose is that if gravity effected the path of a photon based on it's energy ("relativistic" mass) then different wavelenghts of light would have different paths, but all photons regardless of the their energy will have the same path. Don't be seduced by the dark side Ultron, that path leads to planet Ignoramous.
So, as you say, the bending of light is caused by gravity, but gravity in GR is spacetime curvature. You also ignore the fact that light is simply following geodesics in that curved spacetime.
Except if you work out how much light would be deflected by a strictly Newtonian gravitational interaction with the light, you get half the value predicted by GR and of what is actually measured.
Yes, I know that. Suggested reading if you are interested in details: http://sciforums.com/threads/example-about-bending-of-trajectory-near-to-sun.156631/
Really good point. But behold, I have checked what is observed in reality and I was surprised: Observations show that different wavelengths really have different paths. http://www.universetoday.com/107863/gravitational-lens-seen-for-the-first-time-in-gamma-rays/ Interestingly, the delay for the gamma-rays from the lensed blazar takes about a day longer than radio waves to reach the Earth. B0218+357 is also about four times brighter in gamma-rays than in radio wavelengths. This occurs because the gamma-rays are emanating from a slightly different region than radio waves generated by the blazar, and are taking a different path though the gravitational field of the foreground galaxy. My comment: How can they be so sure, that the rays are emanating from so distant and different regions that it takes a whole day in difference? http://www.aanda.org/articles/aa/full/2008/04/aa7014-06/aa7014-06.right.html As for the observational properties of objects whose observed color differences are not reproduced by either differential dust extinction or quasar microlensing, we cannot find any clear difference between these objects and the objects whose observed color differences are well reproduced by either differential dust extinction or quasar microlensing. Therefore, the peculiarity of lens galaxies or lensed quasars is unlikely to be a probable reason for the extreme color differences. It may be more likely that all the observed color differences can be reproduced by a combination of all three possibilities presented in this paper without requiring any special properties of dust and/or the quasar. http://www.earthtimes.org/scitech/quasar-disc-black-hole/1597/ The scientists saw minor differences in the colour of the images over time, partly due to the elements of dust in the galaxies. The light from each of the lensed images took a different journey and its colours provide information about the material in the galaxy. The researchers also found it important to record the extinction law - the journey of the dust and the calculation of how much it blocks out light. http://slideplayer.com/slide/8201571/ My comment: It is explained by dust in galaxies, but we dont really know, if it is because of the dust or just because the gravitational lensing actually really acts as prism.
My comment: None of that in anyway invalidates gravitational lensing and hence curved spacetime. Newtonian refraction occurs at a much smaller value. Gravitational lensing is simply the fact that light also follows geodesic paths in curved spacetime.
...Photons path is dependent on the distance from the lensing object..farther the photon, lessser the deflection....It is ridiculous o say that all photons regardless of their energy will have the same path...
I have been pushing this point for quite some time...but no success. 1. It is a fact that GL does not prove curved space time. 2. Except the lensing by Sun, no other system has proved anything, except existence of lensing. For example in case of Sun, we know the pre lensed and post lensed angles, so we can measure the deflection angles, but IMO no such work is available for any other system. 3. As some one pointed out a comet passing by the Sun will have a deflection, which can be correctly caluclated by Newtonian Mechanism, ie GR can be approximated as Newtonian in certain conditions, then can any of GL supporters answer at what point the deflection starts doubling ? Or this deflection is double only for light and not for any other massed object ?
It's in the quote of mine you mentioned. Rage as much as you like, gravitational lensing is an indication of curved spacetime.
Hmm, are you being dishonest or don't you understand what you are reading. The articles do not support your contention.
If one goes through the articles, the reason that different wavelengths have different paths is because they have different origins. In the first article, the source of gamma radiation is different from the source of visible light. This is a well known phenomena among galaxies. In the second article, the lensing involved makes use of the fact that quasars are different sizes at different wavelengths. This point is raised at the very beginning of the source on quasar microlensing that the second article uses (http://cdsads.u-strasbg.fr/abs/1991AJ....102..864W). The first words of that article are, "The gravitational lens effect is achromatic..." It is the difference in size that results in a color difference, since observation through the lens depends on the angles involved. In the third article, the process used again uses the variability of the color at the quasar and the achromatic nature of lensing. The researchers recorded extinction where possible because extinction is always relevant for astronomical observations outside of our solar system. The slideshow very nicely lays out that the chromatic features of lensing (when redshift is not a factor) are due to either extinction or to the distribution of color in the source.
Nice reply, I appreciate that you have checked the linked sources. It is possible, that the chromatic lensing is caused by dust or by distribution of color in the source, but I dont think the level of observations reached such detail, that it could confidently rule out chromatic gravity lensing.
You are welcome to think that. Given the large numbers of observations in general and the incredible amount of effort given to lensing projects, I'll stick with the opinion of the professionals and not some wild hypothesis.
