eclipse data supporting Einstein

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by nemesis</i>
<br />However, the data confirming Einstein's prediction of light/radio deflection does not necessarily support the "curved spacetime" interpretation, right? Doesn't refraction in a denser elysium atmosphere near a massive body also explain the data?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Right. There were two different physical interpretations of general relativity in Einstein's time, the "geometric" and the "field" interpretations. Both have since been elaborated far beyond what Einstein ever heard of. In particular, Einstein wrote a paper in 1939 arguing that black holes were physically impossible in his theory. Later he worried that the whole theory might need major revision. Fortunately for him and us, he found math that worked and gave the right answers, even though the underlying physics was far from settled. -|Tom|-

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by bdw000</i>
<br />there are other physical effects close to the sun, effects that might be powerful, in fact, compared to a few light rays.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">What did you have in mind? The Sun emits radiation at all wavelengths from x-rays through visual, infrared, microwave, and radio waves. It also throws out energetic particles (ions) in what we call "the solar wind". And it occasionally ejects major amounts of matter in "prominences" and "coronal mass ejection events". These often cause auroras on Earth and disrupt long-range radio communications. Finally, the Sun has a magnetic field that comes and goes, reversing every ~ 11 years.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">The question is: do these eclipse or other EM sorts of experiments take the other effects of the sun into account, or do they know that they are far enough away from the sun that they don't matter?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">None of these "other effects" change eclipses. But we usually see parts of the Sun such as its chromosphere only during total solar eclipses. I mentioned auroras and radio interference above. Whether or not the Sun affects climate in the long term is still debated. -|Tom|-

Tom:

I do not seem to have made myself very clear.

My question is: all that radiation, all those energetic particles, must be fairly dense (if not from the human perspective, at least from the perspective of a photon) close to the sun.

A "wall" of moving protons (thousands of miles thick??) that a photon must pass through seems significant to a nonscientist.

My question is, whatever the density of the radiation and particles in the area used by bending light experiments (the area the starlight must pass through), is it KNOWN that there is zero effect on light? In the lab, do they shine light through turbulent plasma and find that the light is not scattered in the least?

I am sorry if this is extremely elementary. I ask because I have to wonder why some apparently reputable scientists bring this up when questioning relativity (without explaining anything in detail, of course).



Science knows much, but ignores practically everything.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by bdw000</i>
<br />My question is: all that radiation, all those energetic particles, must be fairly dense (if not from the human perspective, at least from the perspective of a photon) close to the sun.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Ah! Now I understand the question.

No, the space near the Sun is extremely sparse, with negligible optical depth. (That means the chances of a photon running into anything on the way out are quite small.) The density of that medium is measured and well known, and it fails by several orders of magnitude to be sufficient to produce the observed light-bending. In fact, at the heights relevant for light-bending (hundreds of thousands of miles above the Sun's surface), the medium is a more perfect vacuum than we can create in most laboratories.

In addition to that data, Einstein predicted the exact amount of light-bending to better than one part in 40,000. What are the odds that the chance density of the solar atmosphere would be just the right amount to match Einstein's prediction so closely?

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">A "wall" of moving protons (thousands of miles thick??) that a photon must pass through seems significant to a nonscientist.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">I sympathize. It is difficult even for astronomers sometimes to grasp the vastness of astronomical scales. For example, there are perhaps a million asteroids crossing Earth's orbit that are big enough to do widespraed damage. Yet Earth encounters one only once a century or less.

If we consider a sphere centered on the Sun with a radius out to Pluto's orbit, that sphere contains enough space to hold all of the 200 billion stars in our Milky Way Galaxy without touching. If we extend the sphere out to the "Oort cloud" at about 50,000 times Earth's distance from the Sun (about 1/5 of the way to the next nearest star), the space inside the sphere can contain all the hundreds of billions of stars in each of the tens of billions of galaxies in the visible universe without touching.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">is it KNOWN that there is zero effect on light?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Yes, it is known that the effect is negligible (not zero).

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">In the lab, do they shine light through turbulent plasma and find that the light is not scattered in the least?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">AFAIK, we can't yet create a vacuum that good in the lab. But yes, the refraction of light in all kinds of mediums has been studied and is well understood and easily modeled. -|Tom|-

bdw000 wrote: “My question is, whatever the density of the radiation and particles in the area used by bending light experiments (the area the starlight must pass through), is it KNOWN that there is zero effect on light?”

The effects aren’t zero, but they are much smaller than the relativistic bending effect. Naturally the possibility of other effects, such as refraction in the “atmosphere” of the Sun, were extensively investigated back in the early 1900’s. In fact, Lorentz and Einstein corresponded on this very subject. Lorentz had performed calculations showing that any refraction effect must be orders of magnitude smaller than the relativistic bending. Of course, with the modern VLBI measurements far from the direction of the Sun, it isn’t even an issue.

nemesis wrote: “However, the data confirming Einstein's prediction of light/radio deflection does not necessarily support the "curved spacetime" interpretation, right? Doesn't refraction in a denser elysium atmosphere near a massive body also explain the data?”

You’ve asked two separate questions there. First, the curved spacetime interpretation is just that, an interpretation, so experimental support for general relativity doesn’t single out one interpretation over another. The different interpretations of general relativity are empirically indistinguishable.

As to you second question, the answer is No, the observed deflection of electromagnetic waves is not consistent with an ordinary refraction effect, for three main reasons. First, refraction is generally dependent on wavelength, whereas the observed gravitational deflection is totally independent of wavelength. Second, refraction is related to density, and the density profile for a putative medium necessary to reproduce the observed gravitational deflection as a function of angular distance from the Sun is inconsistent with any realistic medium. Third, any viable model must also be consistent with the Shapiro time delay effects, and combining these with the light deflection implies a anisotropic medium, which again is inconsistent with any scalar refraction effect. Of course, if you are willing to postulate what amounts to a full tensor field to govern the “refraction”, then you can reproduce general relativity, but that essentially IS general relativity.

tvf wrote: “Do not repeat this kind of remark if you wish to continue posting priveleges here: "it's almost as if a certain kind of individial is literally blind and deaf to current up-to-date reliable scientific information". Keep it about the science, not about any person's views, and all will go well. We are all here to teach and learn, and that process is invariably interrupted by personal remarks of a derogatory nature.”

I think you missed the point… bdw000 posted a message saying Arthur Eddington was “nothing short of dishonest”. I personally think bdw000 has every right to express an opinion like that, because science is practiced by human beings, and human perceptions and judgements are often influenced by our pre-conceived ideas. It’s entirely possible that Eddington presented the 1919 data in a way that was more strongly confirmatory of general relativity than a completely impartial person might have done. So there’s nothing wrong with bdw000 raising that topic… despite the fact that it is, strictly speaking, ad hominem and derogatory.

Now, in my response I didn’t scold bdw000 for his ad hominem comment, I merely made a meta-comment, one that was quite appropriate to the subject he raised, namely, how people are receptive to information that confirms their prior beliefs – exactly as he suggested Eddington had been more receptive to the photographic plates that showed a deflection in agreement with relativity. My observation was that, with all the hundreds of textbooks and references surrounding him, he absorbed only one very atypical and obscure source. This is actually more extreme than the Eddington example, in terms of the comparative quantities of available data and the degree of bias in the implicit selectivity. If it was fair game (and I think it was) for bdw000 to suggest that Arthur Eddington was “nothing short of dishonest” for possibly being influenced by his expectations, then surely it is fair game to point out that the selection of an obscure 1922 article as the basis of one’s knowledge in 2007 could be interpreted as an illustration of the very same human tendency that was the subject of the original message, namely, the tendency to see what we want or expect to see. This isn’t an insult, it’s a characteristic of human beings (including scientists). I think it’s especially appropriate because of bdw000’s signature line: “Science knows much, but ignores practically everything.” Hopefully this makes the exquisite relevance and suitability of my comment more clear.

Thanks everyone (especially Tom) for your comments.

I have learned a lot here. You have saved me hours and hours of searching, just to learn one very simple little bit of common scientific knowlege.

nonneta, I have some comments for you if you are still reading.
First of all, believe it or not, it is fairly difficult to find the exact answers to the sort of questions I have asked, if you do not know where to look. Very little is written for the NON scientist that describes the side issues. They just state the end-result. This is true for many textbooks as well. It may be easy for you to zero in on what you want, not so for me. I probably don't even know the exact words and phrases to use to get decent results at Google.
I also want to point out that I did NOT say "Eddington was dishonest." I very intentionally said, "IF THE BOOK IS ACCURATE . . ," making it plain that I did not even claim to know that it WAS accuate. In fact, my post makes it clear that even if the book was accurate, I wanted to know if it was even relevant: if later evidence was solid, who cares if the book is accurate or not? The reason I am here is because I am well aware that I am not qualified to make judgements one way or the other on this topic, and want other more informed opinions. When some SCIENTIST (a Columbia University professor is probably not a crackpot) makes very sensational claims, I do not want to either swallow it whole, or disregard it alltogether. I want to ask some other scientists what they think.
Despite my signature, and despite what you might think of it, I am a big fan of science.

Science knows much, but ignores practically everything.