Is the universe at least 136 billion years old, is the universe not expanding at all, did the universe begin its expansion when Hubble measured its redshift for the first time or was light twice as fast 13.5 billion years ago than it is today?

[swansont]

2 hours ago, tmdarkmatter said:

It is interesting how simplified this approach is. Instead of light having to pass by individual stars to reach us, the light just needs to pass by a "central point" of the galaxy where you just sum up all the mass of the stars and position that mass on a single point. So when the light passes by stars very closely, according to your calculations these stars would have no mass at all, because you had already summed up their mass in the center of the galaxy. Imagine light having to pass by thousands of stars, each of them deviating by 1.75 arc-sec or even much less. I think this approach is too simple but maybe I am wrong.

 

Light passing by thousands of stars describes a source on the other side of a galaxy (or the far side of a galaxy, viewed edge-on) which we can’t see, because the source is obscured. The effects would tend to cancel, since the deviations are in different directions. 

The stars and galaxies we can image aren’t obscured.

You have yet to articulate how this deviation is a problem. It’s just a bald assertion. Andromeda, for example, has an angular size of 178x63 arc-minutes. You’re worried about deviations a few orders of magnitude smaller.

[tmdarkmatter]

20 hours ago, swansont said:

The deflection formula can be easily found https://adsabs.harvard.edu/full/1929JRASC..23..208T#:~:text=For a light ray running,amounts to B %3D 1'.

It is interesting that on the one hand beyond the distance of 5 solar radii the light ray should be pradically straight and on the other hand from earth we should consider a displacement of 0.49 for Mercury and a displacement of 1.69 for Neptune, while for the observer on Earth it should be considered that the distance to the sun is similar to "infinite". All this does not make sense. If there is only bending very close to the sun, why should there be a huge difference of the displacement between Mercury and Neptune? And what would be the displacement for all of these planets if the observer was further away than Pluto?

[swansont]

2 hours ago, tmdarkmatter said:

It is interesting that on the one hand beyond the distance of 5 solar radii the light ray should be pradically straight and on the other hand from earth we should consider a displacement of 0.49 for Mercury and a displacement of 1.69 for Neptune, while for the observer on Earth it should be considered that the distance to the sun is similar to "infinite". All this does not make sense. If there is only bending very close to the sun, why should there be a huge difference of the displacement between Mercury and Neptune? And what would be the displacement for all of these planets if the observer was further away than Pluto?

The statement about 5 solar radii is in a different part of the paper than the planetary numbers. He isn't talking about the same exact thing. In the discussion related to table 1, you can see that he's discussing the difference between Newton and Einstein, and most of that additional bending is happening  within 5 solar diameters. ("Near point Q the light path is very nearly the same...")  

[tmdarkmatter]

But why would the displacement be different for the different planets? And why would it be so different?

Edited November 25, 2023 by tmdarkmatter

[swansont]

1 hour ago, tmdarkmatter said:

But why would the displacement be different for the different planets? And why would it be so different?

Different distances from the sun. Notice how they are asymptotically increasing toward the 1.75 arcsec for infinite separation.

1.75 arcsec is not a large angle. The other listed angles are, of course, smaller.

[tmdarkmatter]

1 hour ago, swansont said:

Different distances from the sun.

Wait, the text says that these are the displacements of planets once we see them passing close to the sun´s limb from our perspective, right? So why does their displacement depend on the distance to the sun, if the "non negligible" bending only takes place less than 5 solar diameters away from the sun? It would not matter if the planet is 20 solar diameters or 1,000,000 solar diameters away from the sun, because there would be no important effect on the light travelling at this distance from the sun.

What I mean is that according this text the light leaves Jupiter, travels in a straight line towards the sun and is only deviated by the sun´s gravity once it is less than 5 solar diameters away from the sun. And when this light is moving from the sun to earth it is again moving in a straight line. So why does it matter if the straight lines are 1 light second, 1 light minute or 1 light year long? The angle won´t change.

Edited November 25, 2023 by tmdarkmatter

[swansont]

 

 

1 hour ago, tmdarkmatter said:

Wait, the text says that these are the displacements of planets once we see them passing close to the sun´s limb from our perspective, right? So why does their displacement depend on the distance to the sun, if the "non negligible" bending only takes place less than 5 solar diameters away from the sun? It would not matter if the planet is 20 solar diameters or 1,000,000 solar diameters away from the sun, because there would be no important effect on the light travelling at this distance from the sun.

What I mean is that according this text the light leaves Jupiter, travels in a straight line towards the sun and is only deviated by the sun´s gravity once it is less than 5 solar diameters away from the sun. And when this light is moving from the sun to earth it is again moving in a straight line. So why does it matter if the straight lines are 1 light second, 1 light minute or 1 light year long? The angle won´t change.

The discussion of Fig 4 explains why this is happening; the triangle is different, so the apparent shift is different.

[tmdarkmatter]

No there is no explanation of that. The angle should be the same if the object at the sun´s limb is venus or if it is a star several light years away.

On the other hand, they are saying that the angle can be ignored for beeing very small. What happens if we move away 1 light year from the sun. Would the angle change? Because if not and the sun and the star behind it are just two little dots, it might be possible that we would see the star behind the sun on the opposite site of the sun because of this little displacement, so we would be getting a totall wrong image. If that´s the case, all the galaxies we are seeing might be like upside down, because stars we would consider up or down or left or right would actually be on the opposite side, it´s only that the gravitational force of the center of the galaxy distorted the trajectory of the light of its own stars.

[swansont]

3 hours ago, tmdarkmatter said:

No there is no explanation of that. The angle should be the same if the object at the sun´s limb is venus or if it is a star several light years away.

That's odd; it was there yesterday

And, of course, it's shown visually in fig 4 - the lateral displacement is not the same for the planet P as the star, even though the light path is identical.

Quote

On the other hand, they are saying that the angle can be ignored for beeing very small.

Where does it say that? The document is an image, so it's not searchable. At least give a page number.

Quote

What happens if we move away 1 light year from the sun. Would the angle change? Because if not and the sun and the star behind it are just two little dots, it might be possible that we would see the star behind the sun on the opposite site of the sun because of this little displacement, so we would be getting a totall wrong image. If that´s the case, all the galaxies we are seeing might be like upside down, because stars we would consider up or down or left or right would actually be on the opposite side, it´s only that the gravitational force of the center of the galaxy distorted the trajectory of the light of its own stars.

You only see the star that's behind the sun during an eclipse. At any other time the sun is too bright. So unless there are eclipses all over the place, all the time, (and there aren't; we only get this effect on earth because the moon and sun have the same angular size) this is not happening.

And if this were happening with stars close enough to individually resolve, the positions would be shifting as the stars move around and the deflection changed. Do you have any evidence of this?

[tmdarkmatter]

7 hours ago, swansont said:

And, of course, it's shown visually in fig 4 - the lateral displacement is not the same for the planet P as the star, even though the light path is identical.

So, I can imagine that if I was a photon, I would be like driving on a highway and once the highway gets closer to the sun it gets bent and I am forced to travel on this curve, obviously according to the gravitational force of the sun and the distance of the highway from the sun, but after the curve, the highway would just continue completely straight. This is what Einstein is saying. But why would it matter if I have been driving on the highway for a long time on a straight line or if I went on the highway just ahead of this curve? Why would that matter? Shouldn´t we rather think that the curve starts since the beginning at a very low intensity and the only part of really strong curvature is close to the sun? Otherwise, this seems like a refutation of GR, because it cannot explain why the angle is greater in the case of far distances. This space-time curvature is just not flexible enough to explain what we observe and after all we might yet be observing a force pulling the light to the sun and no bending. We can discuss the theory, but we cannot question what we are observing (unless there is something wrong with the measuring devices) and this is not according to what they are saying that the curvature is only significant close to the sun. In the case of Mercury, about 70% of the expected curvature is still missing, because this curvature should be created while light is travelling from infinite to the curve. Therefore, we cannot ignore the curvature created far away from the sun. Instead of having a few very high values of curvature (in a few light seconds), we are having millions of tiny values (during years of travelling) that should be added and altogether sum up for the maximum curvature. In order to observe this maximum curvature, we do not only need to observe stars at very long distances, the observer him/herself has to be very far away too. But at what distance would it still make sense to try to observe an eclipse to investigate this curvature? Did they ever observe an eclipse from Mars, from Jupiter or further away? I think instead of trying to always look ahead, they should first look back at our solar system from these distances to learn more about us. There are only very few images looking back.

Now imagine if we were lucky enough to observe one star passing by in front of another star. What if the light from the star is bent so much that a star on the left switches to the right or a star above switches to below? This should make sense, even if the angles are small.

[swansont]

38 minutes ago, tmdarkmatter said:

So, I can imagine that if I was a photon, I would be like driving on a highway and once the highway gets closer to the sun it gets bent and I am forced to travel on this curve, obviously according to the gravitational force of the sun and the distance of the highway from the sun, but after the curve, the highway would just continue completely straight. This is what Einstein is saying. But why would it matter if I have been driving on the highway for a long time on a straight line or if I went on the highway just ahead of this curve? Why would that matter?

To someone observing you, it matters. The direction you are traveling before the curve is not toward the observer - there is a sideways component. The longer you travel along that initial path, the larger the displacement. But the curvature is the same.

It’s shown in fig 4. The displacement angles are clearly different

[tmdarkmatter]

So, if we play god and we have a star and Mercury in front of us and now take the sun and move it very close to their light, what actually happens is that the original light ray is deviated and absorbed by the surface of the sun. But why do we still see the star or Mercury? It is because another light ray that was not heading into our direction is now beeing deviated by the sun and reaches the observer. So if I take the highway, we are having a highway that is not heading into the direction of the observer but at the sun it is deviated towards the position of the observer, so when we watch from the observers position where the car is getting onto the highway at the next village (mercury) and compare it with the position when the car far away is getting onto the highway (the star), we would see the next town at an angle far closer to the position of the ray arriving at the observer than the city far away. Therefore the difference.

But if we now draw lines to try to figure out the maximum angle, we can see that the angle always increases the further away the star is, but this increase of the angle becomes smaller and smaller and the distances to increase the angle by the same amount becomes longer and longer. So how do they figure out what the maximum angle should be for an infinite distance? I guess there is just a simple logarithmic equation for that. But do they really take the maximum distance of the observable universe to calculate the maximum?

It is interesting to think that a straight line at an angle is actually not straight for the observer once this line reaches very long distances.

And the same happens if we increase the distance of the observer. So the maximum we should consider would be the deviation of light coming from the furthest galaxy passing next to the sun and the observer standing at the other limit of the visible universe.

[swansont]

5 hours ago, tmdarkmatter said:

It is interesting to think that a straight line at an angle is actually not straight for the observer once this line reaches very long distances.

That’s not an accurate summary of the situation.

When you see something, your brain assumes light traveled in a straight line from the object to your eye. If the path curved, then the object isn’t where you see it. Similar to the image of an object in water being displaced owing to refraction. 

Since the light changes direction, the amount displacement depends on how far away it is. If you draw lines to the apparent position and actual position, the angle will depend on the distance to the object. It’s simple geometry. Shown in Fig. 4.

The angle change gets smaller as the distance increases. The final number can be found by taking the limit as distance goes to infinity. As long as the distance is very large compared to the distance from the earth to the sun, the object can be treated as being infinitely far away. The difference between the angle at a few LY and infinity is immeasurably small.