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In 1919 the gravitational lensing by the Sun has been observed during a total solar eclipse. Did someone observe the lensing in any other total eclipses? Last year there was a total eclipse in Chile and there were many scientists observing it. Did they see the stars in different places too? I mean, today it must be even easier to observe it with current telescopes or something. But there is no mention of any other observations than the one in 1919, is there?

astrosnapper
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user30007
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    More interesting variant of this question: are there any historical images from before Einstein made his prediction that show gravitational lensing? – Barmar Jan 27 '20 at 16:26

2 Answers2

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Yes, observations of this kind are within the technical scope of amateur astronomers. Several groups succeeded in replicating the experiment during the 2017 eclipse that crossed the USA.

For example Donald Bruns measured deflections of multiple stars.

Nasa published a "How To" page for anyone wanting to test GR themselves.

James K
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  • Nice. It must be a wonderful feeling to be able to test such an important theory, right in your backyard, with some reasonably affordable equipment. – Eric Duminil Jan 27 '20 at 11:10
  • Does it mean that gravitation indeed is a curvature of spacetime rather than a force? – user30007 Jan 27 '20 at 15:37
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    @user30007: Where have you been for the last 100 years? – TonyK Jan 27 '20 at 15:49
  • @user30007 It could be a force that affects light particles the same way it affects everything else. – JiK Jan 27 '20 at 16:37
  • @TonyK It is a theory that didn't replace Newton's theory but instead both were or still are possible, I dunno. See JiKs comment. – user30007 Jan 27 '20 at 16:43
  • @JiK Light is a massless wave and can only be "attracted" by an object's bending of spacetime. I believe Newton's theory rather than Einstein's because if a probe flies fast enough it isn't attracted as strong as a slower probe by a planet, right? That would be impossible with Einstein's theory, wouldn't it? If space is curved, you'd fall into the bulge, no matter your speed. – user30007 Jan 27 '20 at 16:45
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    @user30007 it's not that one is right and the other is wrong, they both explain some things and don't explain other things. General relativity explains more than Newtonian gravitation does, though (by a wide margin) – llama Jan 27 '20 at 16:56
  • Umm, what? How can both be right? That sounds like doublethink. If you send a probe fast enough to proximity of a celestial body, it won't be affected or not that much, right? That would be impossible with Einstein's theory. I don't oppose it, but just wonder. – user30007 Jan 27 '20 at 17:18
  • @user30007 " I believe Newton's theory rather than Einstein's because if a probe flies fast enough it isn't attracted as strong as a slower probe by a planet, right?" A faster probe experiences the force due to gravity for a much shorter time, and thus appears to be less attracted by the massive object. In reality the magnitude of attraction for two objects equally far away from the planet is the same, it's the duration that they undergo that force that is different. – eps Jan 27 '20 at 17:18
  • @eps You're fully correct, that is what I wanted to tell. As you say "force due to gravity". It would be impossible with Einstein's theory because if there is a spacetime bulge, the probe will change direction and fall onto the body, no matter its speed. – user30007 Jan 27 '20 at 17:20
  • @user30007 In museums they often have a 'coin funnel' (or vortex) where you can put a coin in and it will spin around and around the funnel until it falls in the hole in the middle. What would happen if you increased the speed of the coin? At some point it will be moving so fast that it no longer stays in the funnel but shoots out. This is essentially what happens when the probe shoots past the planet. It is moving so fast that the curvature of space can't keep it contained. Now image a funnel with walls so steep that no amount of speed keeps the coin from falling in. That's a black hole – eps Jan 27 '20 at 17:24
  • @eps Alright, now I understand it, thank you. – user30007 Jan 27 '20 at 17:25
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    @user30007: Newton's theory has been thoroughly superseded by Einstein's theory. When the two theories disagree, it is always Newton's theory that is wrong. Newton's theory is still used today because (i) it is accurate enough for most practical purposes (but not GPS satellites), and (ii) it is easier to calculate with. But it is only an approximation. – TonyK Jan 27 '20 at 17:31
  • @James The maximum deflection for a ray grazing the photosphere is 1.75 arcsecs. The 2.8 arcsecs mentioned in the linked article is the size of the star images. "Accounting for his instrumentation and the conditions during the eclipse, Bruns expected his images of stars to be 2.8 arcseconds across during totality. But to measure the Sun’s deflection of the stars’ light, he needed a precision of just 0.02 arcseconds. So with careful planning and attention to detail, he set out to beat down the errors by imaging multiple stars multiple times." – PM 2Ring Jan 21 '24 at 04:28
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As colleague James K explains in his reply, amateur astronomer Donald Bruns repeated Eddington's 1919 observation during the August 21, 2017 solar eclipse.

For anyone who wants to check out the details, his methodology, observation execution and results are published in the technical article: Gravitational Starlight Deflection Measurements during the 21 August 2017 Total Solar Eclipse

Best regards

Albert
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