# What effect does time dilation have on light?

## Recommended Posts

The question is, if time passes by slower close to heavy masses, what effect does that have on light passing by a heavy object (black hole). According to Einstein, all processes take place slower and, although light keeps travelling at the speed of light, we (from our point of view) should see that this light should pass by slower. In the intergalactic space, however, the total opposite should happen. As time goes by faster and the light there also passes by at the speed of light, from our point of view we should see this light travelling faster than the speed of light as we know it. If this is real, the galaxies we see, should actually be slightly farther away from us, because the light was travelling faster than we think, a light year would be a bigger distance in the intergalactic space. And if we watch the center of our milky way, it should be somewhat closer to us, because the light was travelling slower. A light year would be a smaller distance.

Please tell me what you think.

##### Share on other sites

3 minutes ago, tmdarkmatter said:

from our point of view

You have not defined what “our” point of view is. Are we near the black hole, or are we in intergalactic space, or somewhere else?

If “we” means an observer on earth, then it’s almost the same as intergalactic space.

##### Share on other sites

49 minutes ago, tmdarkmatter said:

The question is, if time passes by slower close to heavy masses, what effect does that have on light passing by a heavy object (black hole). According to Einstein, all processes take place slower and, although light keeps travelling at the speed of light, we (from our point of view) should see that this light should pass by slower. In the intergalactic space, however, the total opposite should happen. As time goes by faster and the light there also passes by at the speed of light, from our point of view we should see this light travelling faster than the speed of light as we know it. If this is real, the galaxies we see, should actually be slightly farther away from us, because the light was travelling faster than we think, a light year would be a bigger distance in the intergalactic space. And if we watch the center of our milky way, it should be somewhat closer to us, because the light was travelling slower. A light year would be a smaller distance.

Please tell me what you think.

This is the difference between "proper" light speed (that measured locally), and the  "coordinate" speed of light,( the speed of light at some distant point, measured by our local units of time and space).

So yes, light passing say, by the surface of the Sun, would appear to be moving just a tad slower than c, as measured by us further out (Though someone at the surface would measure it as moving at c).

How would this effect our measurements of interstellar or intergalactic distances?  Insignificantly.  The very slight difference this might make in any distance measurement is completely overridden by other factors that lower the accuracy of our distance measurements.  In other words we don't claim that our distance measurements are accurate enough in the first place to worry about it. For example, take the star Betelgeuse. It is given a distance of 548 ly with an error of +90 to -49 ly.    This potential error range is magnitudes larger than any  due to a difference between proper and coordinate light speed.

##### Share on other sites

28 minutes ago, Janus said:

It is given a distance of 548 ly with an error of +90 to -49 ly.

Wow, we are still very far away from accurately measuring the universe. I did not know that the measured distances would be that inaccurate!

1 hour ago, swansont said:

Are we near the black hole, or are we in intergalactic space, or somewhere else?

Yes, maybe I would like to know what would be the situation near a black hole AND in the intergalactic space (in comparison).

If close to a black hole, I am wondering that the light surrounding us would be travelling faster than what we would consider "speed of light" at this place. Maybe, because of our proximity to the sun, there should be a very slight effect on our passage of time, so that most of the light surrounding us would be travelling "faster than the speed of light", unless it is at a similar distance or closer to a star of the mass of our sun. But most light should be travelling faster. The average speed of light of the universe might for example be 305,000 km per second or even more at the average distance from stars, if we take this real distance and compare it with the space surrounding Earth. And close to a black hole, this speed might be only 150.000 km per second or even less. Maybe this situation is the cause of why light is getting trapped in a black hole in the first place.

##### Share on other sites

• swansont changed the title to What effect does time dilation have on light?
28 minutes ago, tmdarkmatter said:

Yes, maybe I would like to know what would be the situation near a black hole AND in the intergalactic space (in comparison).

If close to a black hole, I am wondering that the light surrounding us would be travelling faster than what we would consider "speed of light" at this place. Maybe, because of our proximity to the sun, there should be a very slight effect on our passage of time, so that most of the light surrounding us would be travelling "faster than the speed of light", unless it is at a similar distance or closer to a star of the mass of our sun. But most light should be travelling faster. The average speed of light of the universe might for example be 305,000 km per second or even more at the average distance from stars, if we take this real distance and compare it with the space surrounding Earth.

We don’t have to guess, because we can quantify these effects.

“proximity to Earth's gravitational well will cause a clock on the planet's surface to accumulate around 0.0219 fewer seconds over a period of one year than would a distant observer's clock”

A year is 3.15 x 10^7 sec, so this is around a part in 10^9

##### Share on other sites

Yes, but what I can see is that this effect is always being considered as negligible, but if we are close to a black hole, the entire universe surrounding us would change completely.

And maybe the same happens, if we are in the intergalactical space. But the strange thing is that physics currently ignore this effect here, because being for example 25 million light years away from our galaxy according to these equations would be almost the same situation than on earth.

It is strange, but we are currently within a galaxy with a mass of 1,5 10^12 x 2,00 10^27 = 3 10^39 tons and we consider that being 25 million light years away from this mass would not have any effect at all?

##### Share on other sites

48 minutes ago, tmdarkmatter said:

Yes, but what I can see is that this effect is always being considered as negligible, but if we are close to a black hole, the entire universe surrounding us would change completely.

But we are not close to a black hole.

48 minutes ago, tmdarkmatter said:

And maybe the same happens, if we are in the intergalactical space.

No. There is no “maybe”

What happens near a black hole does not happen in intergalactic space.

48 minutes ago, tmdarkmatter said:

But the strange thing is that physics currently ignore this effect here, because being for example 25 million light years away from our galaxy according to these equations would be almost the same situation than on earth.

Because it’s been shown that it can be ignored.

48 minutes ago, tmdarkmatter said:

It is strange, but we are currently within a galaxy with a mass of 1,5 10^12 x 2,00 10^27 = 3 10^39 tons and we consider that being 25 million light years away from this mass would not have any effect at all?

No effect that we need to worry about.

##### Share on other sites

43 minutes ago, swansont said:

What happens near a black hole does not happen in intergalactic space.

I mean the opposite.

43 minutes ago, swansont said:

No effect that we need to worry about.

Please don´t think that I am argueing. It is only a question. I am just curious.

##### Share on other sites

21 minutes ago, tmdarkmatter said:

Because light passes relatively close to the supermassive black hole at the center.

##### Share on other sites

17 minutes ago, swansont said:

Because light passes relatively close to the supermassive black hole at the center.

I am sorry, but even in the "highly simplified" image of Wikipedia it does not seem that the light passes close to the black hole of the "lens galaxy":

The only distances that matter are the distances between source, lense, and observer.

It seem highly improbable that it is the light passing closest to the black hole that we see in the Einstein ring. If you watch the Andromeda galaxie, you can see that the center of the galaxy seems not to be transparent from a distance. Rather this light seems to be passing by the galaxy. If you analyze the sun, it is made of trillions of atoms. The same happens with galaxies, they are made of billions of stars, but work together to create the effect.

##### Share on other sites

2 hours ago, tmdarkmatter said:

I am sorry, but even in the "highly simplified" image of Wikipedia it does not seem that the light passes close to the black hole of the "lens galaxy":

The only distances that matter are the distances between source, lense, and observer.

It seem highly improbable that it is the light passing closest to the black hole that we see in the Einstein ring. If you watch the Andromeda galaxie, you can see that the center of the galaxy seems not to be transparent from a distance. Rather this light seems to be passing by the galaxy. If you analyze the sun, it is made of trillions of atoms. The same happens with galaxies, they are made of billions of stars, but work together to create the effect.

In the derivation, the point of closest approach (impact parameter) is rewritten in terms of these other variables, since the bending angle and distance are related to it. (All parts of a triangle)

##### Share on other sites

17 hours ago, tmdarkmatter said:

I am sorry, but even in the "highly simplified" image of Wikipedia it does not seem that the light passes close to the black hole of the "lens galaxy":

The only distances that matter are the distances between source, lense, and observer.

It seem highly improbable that it is the light passing closest to the black hole that we see in the Einstein ring. If you watch the Andromeda galaxie, you can see that the center of the galaxy seems not to be transparent from a distance. Rather this light seems to be passing by the galaxy. If you analyze the sun, it is made of trillions of atoms. The same happens with galaxies, they are made of billions of stars, but work together to create the effect.

The actual amount of bending of the light path passing by the galaxy is very, very, very tiny.  To see this Einstein ring . we need to be the correct distance from that galaxy in order for the  bent light to converge where we are.   For example, we could use the Sun as a gravitational lens, but to do so, we would need to be 542 AU from the Sun, because light grazing the sun deflects light by just 1.7 seconds of an arc.

Now consider that the galaxy bending the light is billions of ly away, and keeping in mind that just 1 light year is ~117 times longer than 543 AU. Just how much do you think the light passing the galaxy would need to converge on us?  Magnitudes less than it does passing the Sun.

Secondly, Astronomers, astrophysicists, etc. are well aware of the Relativistic effects that exist, and how to calculate them.  If they were a significant issue, they would be factoring them in already.

##### Share on other sites

6 hours ago, Janus said:

Secondly, Astronomers, astrophysicists, etc. are well aware of the Relativistic effects that exist, and how to calculate them.  If they were a significant issue, they would be factoring them in already.

Well, when Einstein came up with his ideas, all physicists were also saying that they are already aware of everything and that there are no more things to discover.

What if time dilatation and light bending in total are not as negligible as initially thought?

Don´t forget that when we are looking at the sky, we are only seeing light! We do not see stars or galaxies, just light. We cannot travel around stars, we cannot touch them.

The more the light is bended and the stronger time dilatation is (and the further away galaxies are), the less does the image we see correspond to reality.

Maybe stars and galaxies are just playing a game with us and nothing we see is actually there.

But there is no way to prove that, unless we travel for a couple of millions of years to at least some neighbor stars.

6 hours ago, Janus said:

Now consider that the galaxy bending the light is billions of ly away, and keeping in mind that just 1 light year is ~117 times longer than 543 AU. Just how much do you think the light passing the galaxy would need to converge on us?  Magnitudes less than it does passing the Sun.

Well, actually, the light is not "converging on us". That´s why we see an Einstein ring. And after passing by the lens, we just have to be lucky enough to have a source galaxy that is at the correct distance (similar to our distance from this galaxy) to see the Einstein ring. But if there was no galaxy behind, the lens effect would exist anyway. Each heavy object is a lens, there are billions of lens surrounding us, each one with a certain angle/strength of bending. And many lens together seem to act as one big lens as well. There are even billions of lens made only of dark matter. But not seeing them does not mean that they are not there. Light might be bending everywhere and stars and galaxies might not be where we would suppose to find them. The same happens with time.

And the light is only being bended at the exact moment when it passes by the lens. The distance between lens and source or lens and observer does not affect the angle or strength of the lens. All the effect should be produced in a couple of thousands of light years (or even less).

##### Share on other sites

55 minutes ago, tmdarkmatter said:

What if time dilatation and light bending in total are not as negligible as initially thought?

This being science, there would have to be evidence of that. The evidence that we have is that relativity works exactly as advertised, to pretty high precision.

Also, it’s “dilation”

55 minutes ago, tmdarkmatter said:

Well, actually, the light is not "converging on us". That´s why we see an Einstein ring.

No, it literally is. Even though the angle is small, if it was not converging, we would not be able to detect it. Supermassive black holes such as the one at the center of the Milky Way, are of order a thousand times larger than the earth

1 hour ago, tmdarkmatter said:

The distance between lens and source or lens and observer does not affect the angle or strength of the lens

Simple geometry tells you that distance affects the angle.

##### Share on other sites

10 hours ago, swansont said:

Also, it’s “dilation”

Further explanation.

Dilation is a general term in English meaning to get larger and applies to many different properties such as the size of an opening, the duration of a time period in relativity, and so on.

Dilatiation is a specific scientific term for an increase ( or decrease if negative)  in volume due to stress (mechanics) or other factors such as pore pressure (earth science).

##### Share on other sites

7 hours ago, studiot said:

Further explanation.

Dilation is a general term in English meaning to get larger and applies to many different properties such as the size of an opening, the duration of a time period in relativity, and so on.

Dilatiation is a specific scientific term for an increase ( or decrease if negative)  in volume due to stress (mechanics) or other factors such as pore pressure (earth science).

I am sorry, this confusion has to do with little differences between languages on how to denominate certain scientific effects, situations or theories.

##### Share on other sites

35 minutes ago, tmdarkmatter said:

I am sorry, this confusion has to do with little differences between languages on how to denominate certain scientific effects, situations or theories.

Don't apologise, +1, it was meant as a helpful comment/piece of information.

We all have to learn these things somewhere along the line.

A good example of dilatation is what happens when you walk on wet sand on the beach.

Edited by studiot
##### Share on other sites

• 4 weeks later...

Please also close this stream and make it disappear. I am not interested in sharing my ideas at a place without freedom of speech.

##### Share on other sites

7 minutes ago, tmdarkmatter said:

I am not interested in sharing my ideas at a place without freedom of speech.

You are free to say anything you want, within the rules that you agreed to, and we are free to disagree with you if we want.  If you can't tolerate criticism of an idea then science is probably not your cup of tea.

##### Share on other sites

Well, saying that something is wrong because it is wrong is not criticism, it is fundamentalism.

##### Share on other sites

On 11/21/2022 at 5:01 PM, tmdarkmatter said:

Well, when Einstein came up with his ideas, all physicists were also saying that they are already aware of everything and that there are no more things to discover.

I don't know how many of the people saying that were physicists, but they've learned their lesson now and they don't say it anymore! 😄

On 11/21/2022 at 5:01 PM, tmdarkmatter said:

What if time dilatation and light bending in total are not as negligible as initially thought?

What if it is? What do you think?

Quote

even in the "highly simplified" image of Wikipedia it does not seem that the light passes close to the black hole of the "lens galaxy"

Quote

According to Einstein, all processes take place slower and, although light keeps travelling at the speed of light, we (from our point of view) should see that this light should pass by slower. In the intergalactic space, however, the total opposite should happen.

This is an interesting question for me. I know the Lorentz transformations are symmetric, so even an observer moving WRT the fixed stars views other objects as time-dilated. But I'm not sure what general relativity says about how observers in gravity wells see things. My short answer would be that the subject has been thoroughly researched, so I'm sure theorists are well aware of any effects that we might experience because of being in a galactic gravity well. Except for that whole "dark matter" thing, of course. They're still working on that one. 😋

Edited by Lorentz Jr
##### Share on other sites

Hi Lorentz Jr.

I do not consider myself to be a physicists. I just like to ask questions.

Considering the negligible part, we should define how negligible it is by repeating the Shapiro time delay starting further away from the sun. What if these 200 msec increase considerably? If we can see Einstein rings, we should suppose that the mass of all the objects of our solar system should combine and increase the effect. And the effect should also increase with the distance from the sun, because the light is travelling at a certain angle for a longer time.

Concerning the Einstein radius, I would like to know what happens to this light being deviated. Does it travel through the lens galaxy?

Another question is, if we can see the Einstein rings and agree to the idea that the light is being deviated, shouldn´t the light coming from stars or galaxies that are not exactly behind a lens galaxy also be manipulated/bended, even if we do not see Einstein rings? If yes, the real position of a galaxy might not only be different due to the distance (and corresponding time of travel) but also because its light is being deviated. There should be some 1000 galaxies between Earth and the furthest galaxies we can see, so shouldn´t their light be extremely deviated? Imagine light coming from a galaxy and passing by the galaxies in between, always on the same side next to the lens galaxies. The angles of the Einstein ring effect should combine and completely deviate the light. But as the light does not travel exactly in a way creating an Einstein ring, we just see a normal galaxy and think that the light of this galaxy was never manipulated.

Is it possible that the light of our milky way travels to the border of our universe and, due to an extensive combination of these Einstein radii, it comes back? What if background radiation is actually light from galaxies coming back home? When thinking about this idea please take into account that we still do not know where the universe ends.

Maybe there will be a point where we cannot see any more galaxies because the light is just getting deviated too much in order to arrive at Earth, so they are invisible to us, just as the light within a black hole is invisible to us because it is being bended inside of it.

Another question is, if light is being deviated by galaxies, shouldn´t this effect also be responsible for the observed red shifting? I know that people already told me that light entering a well and coming out recover its original energy, because otherwise there would be a "loss of energy". But if light has a tiny mass, it should be able to "attract" objects, and this attraction force might be responsible for the tiny "loss of energy" resulting in red shifting.

The problem with the galactic gravity well is that we are also in a "galactic cluster gravity well", a "group of galactic cluster gravity well" and maybe even a "total visible matter well", so the effects of time dilatation should increase the further we look and therefore the light seems to be travelling faster than it should from our point of view, as further away the source is. This also means that the speed of light is completely relative and depends on the surroundings (the present mass). And what happens to light travelling from a galaxy far away to Earth with its speed beeing decreased because in our well it must travel slower? On the other hand light coming from stars close to the black hole in the center of our galaxy is being accelerated on its way towards us, so it should have characteristics that are the opposite of the light coming from far away outside.

Overall, we should say that what we see in the sky might be totally different to what is actually going on out there.

##### Share on other sites

5 minutes ago, tmdarkmatter said:

Considering the negligible part, we should define how negligible it is by repeating the Shapiro time delay starting further away from the sun. What if these 200 msec increase considerably?

It’s been measured using Mercury and Venus, as I’ve already pointed out

7 minutes ago, tmdarkmatter said:

But if light has a tiny mass

It doesn’t, for reasons already given to you.

##### Share on other sites

But I am asking Lorentz this time, not you

##### Share on other sites

34 minutes ago, tmdarkmatter said:

But I am asking Lorentz this time, not you

Sorry @swansont! It's not my fault! 😲

the mass of all the objects of our solar system should combine and increase the effect.

Any masses that are spread out in a solar system or a galaxy can only contribute to lensing of light from other solar systems or galaxies. And that happens. I'm not sure where to look for decent links, but there are photos of lensing around galaxies and galaxy clusters.

Concerning the Einstein radius, I would like to know what happens to this light being deviated. Does it travel through the lens galaxy?

No, it travels around it. It has to stay moderately far away from the galaxy to reach Earth, which is along an almost straight path if the source is directly behind the galaxy.

shouldn´t the light coming from stars or galaxies that are not exactly behind a lens galaxy also be manipulated/bended, even if we do not see Einstein rings?

Yes, that happens. They can even be seen closer to the galaxy, but on the other side, because the light had to be deflected through a larger angle.

There should be some 1000 galaxies between Earth and the furthest galaxies we can see, so shouldn´t their light be extremely deviated?

No, not extremely. Only concentrated mass can generate extreme lensing. The galaxies surrounding the light's path will tend to bend it in the opposite direction, so the overall effect tends to be a wash.

Imagine light coming from a galaxy and passing by the galaxies in between, always on the same side next to the lens galaxies. The angles of the Einstein ring effect should combine and completely deviate the light.

It does. Some of the light from distant sources gets deflected in other directions so we don't see it.

But as the light does not travel exactly in a way creating an Einstein ring, we just see a normal galaxy and think that the light of this galaxy was never manipulated.

Distortion and displacement of the source go hand-in-hand. It's pretty hard for a professional astronomer to miss the distortion. And of course a greater deflection angle means the light got closer to the lens, so there would be even more distortion.

Is it possible that the light of our milky way travels to the border of our universe and, due to an extensive combination of these Einstein radii, it comes back? What if background radiation is actually light from galaxies coming back home?

I'm sure that happens a little bit, but it's not enough to explain the cosmic microwave background. The intensity of light turning all the way around and going in the opposite direction is really low.

Maybe there will be a point where we cannot see any more galaxies because the light is just getting deviated too much in order to arrive at Earth

Maybe someday. That would be a lot of light.

shouldn´t this effect also be responsible for the observed red shifting?

No. The frequency of the light speeds up again once the light is out of the gravity well.

if light has a tiny mass, it should be able to "attract" objects, and this attraction force might be responsible for the tiny "loss of energy" resulting in red shifting.

Red shift has been studied to death. It's not caused by gravitational attraction by the light.

Overall, we should say that what we see in the sky might be totally different to what is actually going on out there.

Maybe so. I'm sure astronomers will consider that possibility if they ever think they have observational evidence for it.

Edited by Lorentz Jr
##### Share on other sites

This topic is now closed to further replies.
×