[Le Repteux (OP)]

Hi everybody,

Here is a drawing representing two light rays curved by the sun's mass: a blue ray coming from a star that brushes past the sun, and a red ray coming from the periphery of the sun itself.



The two rays are parallel when they begin to travel together at the sun's periphery (dotted red and blue arrows), and they thus hit the earth later at the same angle since, being very close to one another, they almost suffer the same curvature (plain red and blue arrows), what gives to the earth observers the impression that both rays come from the same spot in the sky (dotted red and blue lines that lead to the dotted star).

Einstein predicted that the ray coming from the star would get curved by the presence of the sun, but without noticing that the ray from the periphery of the sun itself should also get curved, so he did not realize either that the sun would look wider during this observation, and that he thus would have to shrink it on the mapping of the sky made when the sun was not there to curve the rays.

If he had shrunk his sun on the mapping made when the sun was on the other side of the earth, it would have hidden the same stars than the ones that were hidden during the eclipse, so he could not have concluded that light was effectively curved by gravitation as he had predicted, but instead, that the sun's presence was affecting the direction of the rays in such a way that a mapping made in it's presence kind of widened the sky compared with the one made when it wasn't there.

Notice that this reasoning does not contradict the observations, it only contradicts the explanation of the observations, reason why I placed it on a science forum, but if it's right, then there must be another explanation, and I did not find it yet, except that gravitation kind of widens the sky when our observations are made from a much less massive body than the one we are gravitating around, which means that it could be the real acceleration of the earth observers towards the sun at the microscopic level that would affect the direction of the rays. So far so good, but as I said, it doesn't seem to work, because moving at an angle through a light ray should bend it in the direction of the movement as for the aberration of star light, which would shrink the sky during an eclipse instead of widening it as the observations show, so I am still looking for an explanation.

Anybody finds the idea interesting? Anybody thinks that the rays coming from the sun should also be curved by the gravitation of the sun?

[evan_au]

One minor problem with this argument is that it assumes that a photon emitted near the limb of the solar disk could reliably reach the Earth. The light is emitted from the visible disk of the Sun because the temperature of the Sun is sufficiently high; but at these temperatures, the Sun's atmosphere is effectively opaque to visible light.

In practice, the observation of the bending of starlight near the Sun was conducted with stars that were outside the Sun's visible disk (which was hidden by the Moon's disk, at the time).

[Colin2B]

What evan_au says is correct.
Although many textbooks and articles show light from a distant star grazing the sun, the perimeter of the sun was not used as a reference. The amount of bending is dependant on the distance from the centre of a mass ie the sun. Two photographs of stars were taken, one with the sun nearby (eclipsed) and one without. The 2 were compared and showed the predicted bending.
Having said that, light from the sun is affected by its gravity causing a slight redshift (this can be detected by looking at spectral lines). If the sun's atmosphere was transparent then you could detect an effect similar to that on earth where, due to refraction, we see the setting sun even though it has gone below the horizon. We would see light from a part of the sun's surface just beyond the perimeter, but to be fair the effect would be extremely small.

[mathew_orman]

The light gets refracted by plasma and you can replicate it in a lab... Gravity field has no effect on electromagnetic field of any kind...

[Le Repteux (OP)]

Thanks for answering guys, pleased to meet you! []

Hi Mathew, do you mean that, to your opinion, light is not bent by gravitation?

Hi Collin, if you take another look at my drawing, you will see that the two light rays travel in the same direction once they start traveling nearby together at the sun's perimeter. Being independent from the body where they come from at this point in space and time, do you see any reason why they should experiment a different bending?

Hi Evan, if the light from the star on my drawing gets around the sun, its only because it can travel at that height without being absorbed by the atmosphere of the sun, thus a light emitted by the sun near that height can also travel there if it is tangent to its surface, so it can also reach the earth if it is bent the same. In other words, it cannot travel directly to earth since it would have to cross the sun's surface, but it can certainly reach the earth if it circles the sun for a while as on my drawing.

[mathew_orman]

Thanks for answering guys, pleased to meet you! []

Hi Mathew, do you mean that, to your opinion, light is not bent by gravitation?

 

Yes, in my opinion, based on experimental evidence, gravity has no effect on electromagnetic waves, photons, magnetic fields and electric fields...
But it does affect the frequency of all oscillating structures including pendulum and atomic clocks...
 

[Colin2B]

Hi Mathew, do you mean that, to your opinion, light is not bent by gravitation?

In this section of the forum it is convention, rules and good manners to discuss currently accepted physics theory. If Mathew works in this field and has experimental data that conflicts with accepted theory then I'm sure he will present it in the New Theories section.

....you will see that the two light rays travel in the same direction once they start traveling nearby together at the sun's perimeter. Being independent from the body where they come from at this point in space and time, do you see any reason why they should experiment a different bending?

Just to make sure we are talking about the same issues:
The effect of gravity on magnetic lines of force is negligible under normal circumstances, but is irrelevant to this discussion. Light - photons - have momentum and anything which has momentum is affected by gravity. As you will be aware there are 2 parts to this effect, one predicted by Newton and one we call spacetime curvature predicted by Einstein.
The light rays you show in your diagram would be affected differently because they spend different amounts of time in the gravity field. However, in principle it is possible to imagine 2 rays that do end up parallel but there are some issues to consider. On the sun the effect is exceedingly small and as Evan has pointed out there are atmospheric effects to consider.
Better to look at neutron stars where the diameter is in km and the atmosphere in cm.
The strength of a neutron star's gravity is so great that if does bend light from the far side and we see more than just the face side of the disc. This makes the observed diameter seem larger than it really is. However, the strength of the field also means that the bending is noticeable at a significant distance from the surface - remember the distance to use in bending calculations are from centre of mass rather than from the surface. This is also true of large gravity sources such as galaxies where light bending has been observed at considerable distance from the Galaxy (no atmosphere!).
So I think if you if you use a neutron star as your example it is much easier to consider that your diagram would be correct.

[Le Repteux (OP)]

in my opinion, based on experimental evidence, gravity has no effect on electromagnetic waves

OK! So you don't believe that a light ray from a star is bent by gravitation, but nevertheless, you still think that it is bent by the sun's atmosphere. If my OP is right about both rays being affected by the sun's presence, there would be no bending at the sun's periphery. Its only when the rays would hit the telescopes that they would change directions. So your hypothesis that the rays would be bent by refraction wouldn't work either, because the rays originating from the sun would also suffer refraction, and its diameter would also have to be shrunk on the mapping made when the sun is not there, thus hiding the same stars as when it is there.

[Le Repteux (OP)]

The light rays you show in your diagram would be affected differently because they spend different amounts of time in the gravity field.

Its true that the ray from the star spends twice more time around the sun than the one from the sun itself, but it also travels twice the distance, so its normal that it gets bended twice the angle if it has to hit the earth at the same place.

However, in principle it is possible to imagine 2 rays that do end up parallel but there are some issues to consider. On the sun the effect is exceedingly small

It seems obvious to me that any light ray must be deflected the same if it travels tangentially to the surface of the sun and at the same distance from its center, and its exactly what I show on my drawing.

if you use a neutron star as your example it is much easier to consider that your diagram would be correct

As an example, a neutron star would be more difficult to imagine than the sun, because it doesn't produce visible light and because it has no measurable diameter. When we observe the sun, we see its periphery and we know its because it produces light right there.

[mathew_orman]

Light refraction of plasma medium is a conventionally accepted physical phenomena...
Example: http://journals.aps.org/pr/abstract/10.1103/PhysRev.162.117
Or, is the San disobeying the low of refraction?

[RD]

... Anybody thinks that the rays coming from the sun should also be curved by the gravitation of the sun?

Sun will appear very slightly bigger because of gravitational-lensing ...
https://van.physics.illinois.edu/QA/listing.php?id=21717&t=gravitational-lensing-of-the-sun

[PmbPhy]

One minor problem with this argument is that it assumes that a photon emitted near the limb of the solar disk could reliably reach the Earth. The light is emitted from the visible disk of the Sun because the temperature of the Sun is sufficiently high; but at these temperatures, the Sun's atmosphere is effectively opaque to visible light.

Such things are of no consequence to the idea that the OP is trying to get at.

[evan_au]

if you use a neutron star as your example it is much easier to consider that your diagram would be correct

As an example, a neutron star would be more difficult to imagine than the sun, because it doesn't produce visible light and because it has no measurable diameter.

I think that this latter comment was referring to a black hole, rather than a neutron star.

A neutron star has a definite surface, and a very compressed atmosphere (perhaps μm thick).
They are very hot (at least initially), and will produce visible light as well as X-Rays.

[Le Repteux (OP)]

As an example, a neutron star would be more difficult to imagine than the sun, because it doesn't produce visible light and because it has no measurable diameter.

I think that this latter comment was referring to a black hole, rather than a neutron star.

A neutron star has a definite surface, and a very compressed atmosphere (perhaps μm thick).
They are very hot (at least initially), and will produce visible light as well as X-Rays.

Sorry, I didn't know that neutron stars had electrons, but what I meant by measurable diameter is that the optical angle cannot be observed directly, whereas the sun's one can. Its the sun's observed diameter that we need to compare the mappings, and if its light was bent, it would look larger than what it is for real, so it would have to be shrunk on the mapping made when it isn't there, and it would thus hide the same stars as when it was there.

Sun will appear very slightly bigger because of gravitational-lensing ...
https://van.physics.illinois.edu/QA/listing.php?id=21717&t=gravitational-lensing-of-the-sun

Thanks for the link RD, I could not find any myself.

Here is the answer:

"The curvature, however, will be only half as big since the first half of the curving path from another star isn't there.
There is, however, another effect. Maybe by the "real" size you mean the distance across the sun, as measured by some local ruler. (Ok, let's not worry too much about the practicality.) That distance is bigger than you would think from the apparent area or circumference, because of the way gravity warps space-time inside the sun. This effect on the apparent size is less than from the light curvature by a factor of about R/L, where R is the sun's radius and L is the distance from us to the sun. So it's pretty small compared to the light curvature effect.

Mike W."

On my drawing, the curvature is also half the one from the star, which is normal since it wouldn't follow the other ray if it was bent more. So I think that this part of the answer might be wrong, and as Mike himself points out, it is by far the important one. Maybe he answered without bothering to make a drawing?

Light refraction of plasma medium is a conventionally accepted physical phenomena...
Example: http://journals.aps.org/pr/abstract/10.1103/PhysRev.162.117
Or, is the San disobeying the low of refraction?

The way I understand it, during an eclipse, the gravitation from the sun is affecting the position of all the stars that we observe at that moment, and most of them appear far away from the sun's perimeter, so their light doesn't have to go through the sun's atmosphere to reach us. If it is so, then refraction wouldn't affect those rays, so how would you explain their bending?

[Colin2B]

Light refraction of plasma medium is a conventionally accepted physical phenomena...

True, but that is a long way from providing an alternative theory to explain gravitational bending of light. Not only would you have to explain how this works for the sun, but also for all the other experiments and observations. As I say, if you have experimental evidence to support your assertions the best place to post it is in New Theories.

The way I understand it, gravitation from the sun during an eclipse is affecting the position of all the stars that we observe at that moment, which means that most of them appear far away from the sun's perimeter, so that their light doesn't have to go through the sun's atmosphere to be bent. If it is so, then refraction wouldn't affect those rays, so how would you explain their bending?

Yes, the stars measured were away from the sun's perimeter.
Also the refractive index of a plasma is frequency dependant, but observations show the bending to be frequency independant.

[Le Repteux (OP)]

...the refractive index of a plasma is frequency dependent, but observations show the bending to be frequency independent.

Good observation Collin! If bending was due to refraction, the observed bended rays would not carry all the colors that the star emits when the sun is not there.

[Colin2B]

Good observation Collin!

Sorry, I can't claim the observation. It came from early work on radio astronomy where it is easier to observe radio sources without waiting for an eclipse.
It's a fascinating universe we live in  []

[Le Repteux (OP)]

You mean that you observed a refraction phenomenon when the source was near the sun? That some of the frequencies vanished?

[Colin2B]

You mean that you observed a refraction phenomenon when the source was near the sun? That some of the frequencies vanished?

No, I was reporting earlier work with radio sources passing through a plasma, the degree of bend was dependant on frequency as is predicted by theory.
With gravitational bending there is no frequency dependency. However, when observing radio sources close to the sun, you need to make allowance for this additional frequency dependant bending.
Frequency is very important with plasmas. The plasma can be transparent, reflective or absorbent dependant on the frequency of the source.

[mathew_orman]

Rainbow effect is internal to planets atmosphere  just like we see at sunset...
Also, where are the pictures of assumed gravitational lensing of Sun or any other eclipse?