Very cool:

http://www.skyandtelescope.com/astronomy...xperiment/


But, for those who do not want to read the whole article (or, part of it), here's the first paragraph:

Quote:In the August 2016 issue of Sky & Telescope, I explained that I was going to set up an experiment to measure the gravitational deflection of stars one year later. I did go to Wyoming for the Great American Eclipse, and I experienced perfect conditions that led to an incredibly precise result! This is the first time — since Sir Arthur Eddington traveled to Africa to witness the 1919 eclipse — that the experiment went just as planned, with no weather or equipment problems. While there is no new science in this result, being able to accomplish this very difficult experiment for the first time in nearly 100 years was a wonderful experience.

And, an image:

The 1919 observations were quite the sensation.

Nice to see interest persists in the eclipse technique.

Thats so cool man. Astrophysics are very neat.

Einstein not only predicted the effect, but calculated the magnitude of the shift.

We don't have ANYTHING of comparable caliber from all the damn religious prophets the world has seen in the last 5000 years.

But...but....but... they hear voices.  Doesn't that count?

They gotta be correct.

Whodda thought that would be such an impossible standard ?

And the Joe Smith technique of retroactively changing the prediction to match what happened ain't very nice either !!!

BTW, speaking of space/astronomy, old Horny Joe alternately describes Kolob as a planet and a star . . .

Almost as though Joe did not know the difference.

From the article:

Quote: According to his theory of general relativity, gravity warps spacetime itself, which bends the path of massless photons.

Obviously I'm not a physicist, but I can't wrap my head around this. I don't know what they mean by spacetine or how gravity could affect something without mass. So the rest of the experiment doesn't make sense to me Does anyone know of any good resources to understand the concept of general relativity?

(February 17, 2018 at 4:31 pm)shadow Wrote: From the article:

Quote: According to his theory of general relativity, gravity warps spacetime itself, which bends the path of massless photons.

Obviously I'm not a physicist, but I can't wrap my head around this. I don't know what they mean by spacetine or how gravity could affect something without mass. So the rest of the experiment doesn't make sense to me Does anyone know of any good resources to understand the concept of general relativity?

Well, spacetime is exactly what it sounds like: space plus time. In other words, all space and all time.

Any mass (or energy, actually) will cause a curvature of spacetime locally according to Einstein's equations. This change in spacetime, in turn, affects the movement of matter and energy. It's a type of feedback loop.

In this experiment, the mass of the sun causes a distortion of space and time close to the sun which causes light going past to move away from the straight line path.

Now, for even something of the mass of the sun, this is a very small effect: the shift of 1.7 second of arc is equivalent to the size of a dime as seen from around 1 1/4 miles away.

More remarkably, the Newtonian prediction is half that amount. So they needed to determine the position of a star in the sky precisely enough to tell whether it was off by the size of a dime at 2 1/2 miles away.

if you want to understand GR better, it is best to first understand special relativity (where the concept of spacetime is investigated) and be prepared for some mind stretching stuff.

As far as the stars photon is concerned, it did follow a straight line to get here.

But we noticed it went near to our sun to do so and Einstein noticed space itself is warped around the sun, so we see the photon as having changed direction slightly.

That's why it's called relativity, the photon didn't notice anything on the way here but we did. It's relative to who does the measuring.

BTW, the 1.7 arcsecond deflection is for photons that just graze the edge of the sun, the further out you get the less deflection. The effect has been noticed with starlight, radio waves from quasars, and even our space probes as they arc behind the sun. In that last example there are also time effects we can discern from the accurate signals our probes send.

Gamma rays moving upwards from earth's surface have been demonstrated to be measurably weakened by earth's gravitational field, btw. An amazingly delicate and subtle experiment. As I recall the effect was noticeable in a height of around 50 feet.

Here's the math; short and sweet:

https://sites.math.washington.edu/~morro...Genrel.pdf