For this, nothing better than a german Physicist....

Whatever happened to Alex K? Last I heard he was busy with teaching teenagers physics. Hmmm can't imagine a tougher job

Give that man a beer!
Good work

(February 16, 2018 at 6:55 pm)Jehanne Wrote: 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:

I find it utterly impossible to believe this experiment was not successfully performed emany times, either directly or incidentally, in the intervening 100 years.

If that were indeed the case, then eddington’s original experiment would have been dismissed as a fluke.

Also, distinguishing a positional difference of 1.7 arc seconds is not trivial with amateur equipment and i wonder whether it was relativity or wistfulness that underlie this particular observation.

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(February 18, 2018 at 11:02 am)LastPoet Wrote: For this, nothing better than a german Physicist....

Whatever happened to Alex K? Last I heard he was busy with teaching teenagers physics. Hmmm can't imagine a tougher job

Teaching teenagers physics is easily done.  Just drop two of them out of a window and they learn Doppler effect, constant gravitation acceleration, interchange of kinetic and potential energy, and inelastic collisions, all in just a few seconds.

(February 18, 2018 at 2:47 pm)Anomalocaris Wrote:

(February 16, 2018 at 6:55 pm)Jehanne Wrote: 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:

And, an image:

I find it utterly impossible to believe this experiment was not successfully performed emany times, either directly or incidentally, in the intervening 100 years.

If that were indeed the case, then eddington’s original experiment would have been dismissed as a fluke.

Also, distinguishing a positional difference of 1.7 arc seconds is not trivial with amateur equipment and i wonder whether it was relativity or wistfulness that underlie this particular observation.

---

Variants of this experiment have been done. For example, we have measured the deflection of radio waves going past the sun from quasars and timing delays from other radio waves.

But the observation during an eclipse is both very tricky and requires the eclipse to happen when the sun (in the sky) is close to a bright enough star whose position is known *precisely*. That 1.7 second of arc is incredibly hard to measure unless there are other stars in the field of view so you can compare 'eclipse pics' with 'not eclipse pics' to pick up the deflection. Even small distortions from the optics can wreck havoc with this measurement.

(February 18, 2018 at 2:47 pm)Anomalocaris Wrote:

(February 16, 2018 at 6:55 pm)Jehanne Wrote: 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:

And, an image:

I find it utterly impossible to believe this experiment was not successfully performed emany times, either directly or incidentally, in the intervening 100 years.

If that were indeed the case, then eddington’s original experiment would have been dismissed as a fluke.

Also, distinguishing a positional difference of 1.7 arc seconds is not trivial with amateur equipment and i wonder whether it was relativity or wistfulness that underlie this particular observation.

---

(February 18, 2018 at 11:02 am)LastPoet Wrote: For this, nothing better than a german Physicist....

Whatever happened to Alex K? Last I heard he was busy with teaching teenagers physics. Hmmm can't imagine a tougher job

Teaching teenagers physics is easily done.  Just drop two of them out of a window and they learn Doppler effect, constant gravitation acceleration, interchange of kinetic and potential energy, and inelastic collisions, all in just a few seconds.

I'm fairly sure this principle is used to measure the mass of "invisible" space objects, since their effect on the space time is to focus photons from more distance sources of light.

Eclipses generally don't happen in very convenient places either.

If one wants to repeat the observations one must transport the relevant equipment to the site of the next appropriate eclipse and then hope the day of it's not cloudy.

Additionally, as totality approaches a given location, there is a cooling effect as the shadow of the moon blocks the suns heat. There can be atmospheric turbulence effects that can make discerning the precise images on the photographs more difficult.

Another factor with modern imaging devices, you will need a wide field of view (several degrees) and a high pixel count to accurately record deflections in the arc-second range. It takes a whole bunch of pixels to do this.

(February 23, 2018 at 6:13 pm)Tobie Wrote:

(February 18, 2018 at 2:47 pm)Anomalocaris Wrote: I find it utterly impossible to believe this experiment was not successfully performed emany times, either directly or incidentally, in the intervening 100 years.

If that were indeed the case, then eddington’s original experiment would have been dismissed as a fluke.

Also, distinguishing a positional difference of 1.7 arc seconds is not trivial with amateur equipment and i wonder whether it was relativity or wistfulness that underlie this particular observation.

---

Teaching teenagers physics is easily done.  Just drop two of them out of a window and they learn Doppler effect, constant gravitation acceleration, interchange of kinetic and potential energy, and inelastic collisions, all in just a few seconds.

I'm fairly sure this principle is used to measure the mass of "invisible" space objects, since their effect on the space time is to focus photons from more distance sources of light.

yes, indeed. It is one of the major ways of mapping out the distribution of dark matter.

How do we know that there isn't something else in space that bends light?

Water bends light, and in the right conditions you can't visually prove that it is in between the eye and the object.

Is it possible that space is filled with something which isn't percieved by material beings and their material instruments?

While an absense of physical evidence isn't a licence for the imagination, it is presumptuous to say that what is observable is the only truth.

(March 2, 2018 at 5:44 pm)Banned Wrote: How do we know that there isn't something else in space that bends light?

Water bends light, and in the right conditions you can't visually prove that it is in between the eye and the object.

Is it possible that space is filled with something which isn't percieved by material beings and their material instruments?

While an absense of physical evidence isn't a licence for the imagination, it is presumptuous to say that what is observable is the only truth.

Well, in a sense, that is how we discovered dark matter and how we investigate its properties. Dark matter doesn't interact with ordinary matter or light very strongly (if at all). So in a sense, it satisfies your criteria.

We use the way that dark matter bends light to map out where it is and how much is there. We do that by looking at slight distortions in the way light travels from more distant objects. So, there is a sense in which we are detecting the water just as you suggested.

(March 2, 2018 at 6:55 pm)polymath257 Wrote: Well, in a sense, that is how we discovered dark matter and how we investigate its properties. Dark matter doesn't interact with ordinary matter or light very strongly (if at all). So in a sense, it satisfies your criteria.

We use the way that dark matter bends light to map out where it is and how much is there. We do that by looking at slight distortions in the way light travels from more distant objects. So, there is a sense in which we are detecting the water just as you suggested.

That's what I was thinking, although I haven't heard of applying dark matter to light bending.