How do we know gravity bends light? Different Approach to GR

[metacogitans]

What proof is there other than gravitational lensing during a solar eclipse?

Consider:

a) all the examples of 'gravitational lensing' occuring in pictures taken by hubble are obscured depictions of it, and none show with a decent certainty that gravity is responsible; it could be just as likely that the lensing was caused by light diffracting as it travels through a medium (i.e., space dust).

b) a picture of a black hole where light is lensing dramatically due to gravity would be sufficient enough evidence to close the books on this case; unfortunately, Hubble nor anything/anyone else has ever taken a picture of such a thing - every picture you've seen of a black hole online with light bending wildly around it was simulated.

 

If the gravitational lensing observed during the 1919 Solar Eclipse Experiment is the only evidence (where the change in location is significant enough that the distance it moved is noticeable with the naked eye) we have supporting the idea that gravity bends light due to the geodesics of 'warped spacetime', then this idea that gravity affects light, which is popularly included in the philosophy behind General Relativity, seems fairly unfounded.

The idea is commonly packaged as part of the philosophy behind General Relativity; although in a strictly mathematical sense, the field equations in General Relativity tell us nothing about how light behaves - it is strictly a set of mathematical equations for calculating gravity produced by mass - so I'm not saying that General Relativity is wrong, just that the philosophy often promoted alongside it as an approach to the concepts is wrong. The tensors, of course, involve a Euclidean grid that is warped, hence 'warped space-time', but any physics using tensor calculus also involves changes in a Euclidean grid, and someone could come along and call it 'warped space-time' (assuming time is included as its own coordinate) if they wanted to, and be just as correct.

As an alternative explanation to the 1919 Solar Eclipse Experiment, we could, for example, say that as the light passed by the sun, it interacted with gas particles in the sun's upper atmosphere, causing it to bend (the same as it would when passing through any medium where density increases).

If that's the case, then maybe we could take an alternative approach to the philosophy behind 'warped space-time' described in General Relativity as well. Let me make it clear though that I am not posting my own alternative theory. I repeat, I am not posting my own alternative theory. If I was posting an alternative theory, the equation would have to be different, but the math is exactly the same, I'm still using the field equations in GR - so I'm not posting a made up alternative theory and not breaking any rules. Just making that clear. I'm just posting a different possible approach to the concepts in General Relativity, like how there's multiple different ways people go about long hand multiplication, some people start at the left digit, some people start at the right digit, some people break the number they're multiplying up into chunks - all approaches give you the right answer, and just because your approach is different doesn't mean it somehow ceased to be multiplication and became some arbitrary 'alternative' alchemical ritual of yours that uses bizarre esoteric subscript or something.

 

We can give an explanation for what is actually happening with gravity using General Relativity without just saying 'the underlying grid of space-time itself is curved' and dropping it at that without any further explanation: Bodies of massive particles (be it planets, stars, celestial gas clouds, etcs) essentially act as speed traps for electromagnetic radiation. An electromagnetic wave can not pass right through the body of massive particles, but instead ends up bouncing around back and forth between the particles -- the body of massive particles effectively absorbs the electromagnetic radiation for a short while, slowly dispersing it in various directions.

Because of this, bodies of massive particles act like giant hubs of electromagnetic activity -- electromagnetic radiation shoots out randomly from the body of particles in different directions; so for any particle approaching from outer space, the closer it gets to this body of particles, the more it starts getting pushed and pulled in different directions by electromagnetic radiation coming from the body of particles. This vibration in different directions (the German word is Zitterbewegung) means that the closer the particle is to the body of particles, the more it will be vibrating sporadically in all directions, and the longer it takes for the particle to travel the same distance when a force is applied, affecting the particle's initial velocity.

Not only will this cause the particle to curve towards the body of particles, but the effect of this phenomenon accumulates exponentially (as the closer it gets to the body of massive particles due to curving towards it, the more its Zitterbewegung will increase from interacting with electromagnetic radiation from the body of massive particles), causing the particle to accelerate.

This is mathematically identitcal to the 'spacetime' curvature in a gravity well described by the tensors in the Einstein Field Equations, and we are able to incorporate 'warped space-time' into our understanding of General Relativity without having to say whether light is curved by gravity or not, and also without claiming there's 'underlying grid to the universe called space-time and its responsible for all of gravity'. We are able to explain time-dilation, saying time-dilation occurs the closer you get to a massive object, where the same amount of force applied to an object takes a longer amount of time to make the object move the same distance - except in our new approach, the time-dilation is caused by Zitterbewegung and not the 'invisible grid of space-time underlying everything being curved' without being able to explain what that grid is made of or why mass curves it - in our approach, the grid of 'space-time' is strictly a mathematical device that comes with tensor calculus, which Einstein needed to be able to explain gravity without violating Special Relativity (that was, after all, what General Relativity's goal was).

If everything in our approach is flush, then the older popular approach where the "underlying grid of the universe called 'space-time' being curved is the sole source of gravity" seems to be quite wrong; it's an outdated, archaic, and inappropriate (for additional reasons I'll get into shortly) way to be introduced to the concepts of General Relativty

 

If you ask me, Einstein's General Relativity never suggested there to be an underlying grid of 'space-time' in the first place; the tensor calculus used in the Einstein field equations simply describes gravity in terms of a Euclidean grid (where space is given its own coordinate) that is warped. Any physics which uses tensor calculus is also explaining things in terms of changes in a Euclidean grid.

Following logic, the burden of proof is on supporters of the idea that gravity affects light, as the result of the solar eclipse experiment was not definite evidence supporting their approach, as other possible explanations exist; it wouldn't be right for the burden of proof to be placed on me to have to disprove their approach without it having evidence to support it in the first place. Why would I have to show proof that gravity doesn't bend light? They still need to prove it does bend light!

Both approaches are consistent with the results 1919 Solar Eclipse experiment, as well as the math of the Einstein Field Equations in GR; as far as I see it, both approaches have a similar possibility to be valid given that the only evidence supporting either rests on whether light from the star in the 1919 experiment bent near the sun because of gravity or because it diffracted in the sun's upper atmosphere.

 

In my opinion, my approach makes more sense, and my approach also leaves out one big hole in understanding:

If curved space-time were the only factor involved in gravitation, it is a mystery how free-fall can be initiated when an object is at rest relative to the source of the gravity, since in order for curved space-time to produce something resembling gravitation by itself, the object has to be moving.

Light takes longer to travel through a medium of massive particles because it ricochets off particles in the medium, causing its path to no longer be a perfectly straight line and therefore making its travel time in one direction longer. When light is being 'held up' in its travel time when passing through a group of massive particles (or in the case of denser groups or 'bodies' of massive particles, like planets and stars, the light is absorbed and slowly disperses from the group/body of particles in many directions), the light is being diffracted by the medium (although for denser groups of particles, 'diffracted' might not be the most appropriate term), which causes the radiation to contribute to the Zitterbewegung (German for trembling motion) of any particles it interacts with.

This Zitterbewegung, assuming it is being experienced in all directions by a particle, affects the particles velocity in the same way as curved space-time traditionally does in General Relativity; simply speaking, it causes the particles trajectory to curve and causes the particle to slow down in the direction of the body/group of massive particles, which is essentially the same as time-dilation described in the philosophy behind General Relativity, in that it takes a longer time for the same amount of force to make an object/particle travel a certain distance (but from the reference point of the object/particle of course, it traveled the normal distance one would expect to travel during an increment of time from the force applied, as there is no noticeable change in the passage of time locally).

The closer it gets to the group of massive particles, the more Zitterebewegung-inducing radiation it will encounter, causing it to move sporadically even more (and also mitigating its initial velocity even more as well); while the particle is vibrating, any instance where it vibrates in the direction of the body of massive particles, it will experience Zitterbewegung even more - which means the effect is self-sustaining and self-initiating, which is what we would expect with free-fall.

 

As an afternote, I don't know if I'm the first person to ever explain GR in terms of Zitterbewegung and EM radiation, but if I am and there turns out to be a consensus on it, I'd hope credit gets traced back to me. I spend a lot of time on physics; if it ever turned out that an idea I had was something new and significant, it'd be nice to see things pay off by being acknowledged for it. I got that 'breakthrough' feeling tonight and almost didn't want to put it online, because if it was a breakthrough I might just be giving it to everyone else.

 

Q. "Do I have any experimental evidence supporting this approach?"
A. "No, I have a fuzzy photograph with a bunch of different colored blotches on it, with numbers and arrows all over it pointing at different things, and then at the top of the photograph I wrote 'Gravitational Lensing' in marker." Citation: http://www.nasa.gov/sites/default/files/14-283_0.jpg (if you search the internet for proof of gravitational lensing, that's what you find, among a few other similarly lackluster photos the physics community deems 'photo evidence' of gravitational lensing; "you see that smaller smudge? In this photo, it looks like its moved over a little bit more because there's this big smudge in front of it.. or maybe the light from the big smudge just makes the small smudge a little harder to see so it looks like it moved, I don't know I can't tell, the resolution on these photos is so terrible, at the scale to actually look at something, you can only see a handful of pixels and we tell people, "oh yeah that's signature pattern of a quasar there" and "oh you can tell that star is close to having a supernova", and if anyone doubts us we tell them our conclusions are backed up by super-sensitive instruments and equipments that measure small fluctuations which we use to support all the claims we make.. when really, this is all just guesswork, I mean, it's not like anyone will ever actually know, it's not like we'll ever be able to go to these galaxies and take a look to check if all our equipment on the space satellite was working.. I mean, it's going to either kinda work, or kinda not, we sent stuff up into space to take pictures of far away galaxies, that's the first time anyone's ever made something to try to do that, we had nothing to compare it to before building it. I'm just amazed the damn thing sends anything back at all, that's a plus. At least this way we can argue over what various blotchy smudges mean and get paid for it, when the odds are just as good that the blotchy smudges are actually just our equipment malfunctioning, because there's no benchmark here, we have nothing similar to it to even know if its been working right").

Edited June 25, 2015 by metacogitans

[Klaynos]

I've not read your whole post. It's quite long. But I did note the lack of maths.

 

GR makes precise numerical predictions about gravitational lensing. These predictions match the observed evidence (again using maths). To supplant GR on this regard you would need to make better predictions using maths. It's not just about comparing pictures. The observations have also been repeated.

[ajb]

The not so great evidence from 1919 is not al the evidence that we have. Much better images of gravitational lensing have been captured and these all agree well with general relativity, which does tell us about the motion of classical light beams. Light follows null geodesics.

[metacogitans]

I've not read your whole post. It's quite long. But I did note the lack of maths.

 

GR makes precise numerical predictions about gravitational lensing. These predictions match the observed evidence (again using maths). To supplant GR on this regard you would need to make better predictions using maths. It's not just about comparing pictures. The observations have also been repeated.

Here's the Einstein field equation:

Not as crazy mathematically as it looks at first glance; you have some tensors and constants basically.

G is the gravitational constant, c is the speed of light in a vacuum, the capital lambda is the cosmoglogical constant (this is not essential to the equation for gravity, and was added to the equation by Einstein some time later after he introduced the equation)

and the tensors from right to left; R mu nu is the Ricci Curvature Tensor, the g mu nu is the metric tensor, R is the scalar curvature, and T mu nu is the stress-energy tensor.

 

We don't need to know the tensors in detail, all we need to know is that they ultimately describe the curvature of the Euclidean grid (space with its own coordinate included) caused by mass, which can be used to calculate the effect of gravity. The equation is often intepretted as 'mass telling space how to be shaped' and 'space telling mass how to move'.

 

Now, that equation is strictly used to calculate an objects path through space-time under the effect of gravity resulting from a given mass; it doesn't tell us whether light is subject to gravity as well - after all, light is massless according to most people you ask. It certainly doesn't make 'precise numerical predictions about gravitational lensing'.

 

The real reason Einstein and co ever thought gravity affected light, and how that played a role in the delevopment of GR, is because of a thought experiment:

If you are in a box on Earth with downward gravitational force g, and then you're in a box thats flying in outer space accelerating at the force g, you will not be able to tell the difference between the two. Now, if you shine a light through a window in the box thats flying through outer space, the light would curve towards the floor of the box because it is accelerating. Because of this, it is assumed that light would also curve if shined through a window in the box on Earth due to gravity.

 

That thought experiment lead to a series of deductions which lead to the correct prediction that the time dilation and length contraction described in special relativity must also be true with gravity.

 

But, the idea that gravity bends light ultimately comes from a series of assumptions and thought experiments, and its basis in reality is highly questionable. If you disagree, please explain to me its basis in reality in detail.

The not so great evidence from 1919 is not al the evidence that we have. Much better images of gravitational lensing have been captured and these all agree well with general relativity, which does tell us about the motion of classical light beams. Light follows null geodesics.

One thing I was thinking is that light could follow the geodesics in curved spacetime described by GR, but is not subject to gravitational attraction (light won't enter free fall or accelerate exponentially due to gravity) since light is massless.

Those geodesics are, I believe, the consequence of another phenomenon: there is no objective notion of 'location, or, 'there is no underlying grid of space'. Whatever 'space' is, it has to be made of something, and since two things can not occupy the same location simultaneously, an object/particle with mass displaces space, causing space to have a higher density around the massive particle/object. This ties in with the idea that a particle only has location relative to other particles it is in immediate contact with in its surroundings.

 

So does that mean light is subject to gravitation though really? Light doesn't start accelerating exponentially due to gravity. Or is it just the path light takes when travelling through certain mediums?

 

That only explains the geodesics of space-time though, right? Which is only one part of General Relativity's explanation for gravity.

 

Like, light is not experiencing attraction from gravity, it's just moving through 'stuff', which is all that space is: 'stuff' in a big soup with other 'stuff', and having 'a bunch of stuff' in a small region of space results in that 'bunch of stuff' displacing the 'stuff' and giving it a higher density in certain regions than others. So when light appears to be taking a curved path, the path it took was actually a straight line through 'stuff' (with 'stuff' being whatever spacetime itself is made out of).

Edited June 25, 2015 by metacogitans

[ajb]

The field equations of GR tell you how the matter/fields couple to space-time geometry. You see this is via the energy-momentum tensor. Thus, any fields that carry energy-momentum can at as sources of gravity. Thus, light can act as a source of gravity.

 

Now, this does not tell you anything about the motion of test particles, massive or massless. Like electromagnetic theory, one needs to add the equation that describes the force on a particle. In EM this is the Lorentz force, in GR we use the geodesic equation. In short, the geodesics tell how test particles move under the influence of gravity, where we understand gravity as the local geometry.

[metacogitans]

Bodies of massive particles (be it planets, stars, celestial gas clouds, etcs) essentially act as speed traps for electromagnetic radiation. An electromagnetic wave can not pass right through the body of massive particles, but instead ends up bouncing around back and forth between the particles -- the body of massive particles effectively absorbs the electromagnetic radiation for a short while, slowly dispersing it in various directions.

 

Because of this, bodies of massive particles act like giant hubs of electromagnetic activity -- electromagnetic radiation shoots out randomly from the body of particles in different directions; so for any particle approaching from outer space, the closer it gets to this body of particles, the more it starts getting pushed and pulled in different directions by electromagnetic radiation coming from the body of particles. This vibration in different directions (the German word is Zitterbewegung) means that the closer the particle is to the body of particles, the more it will be vibrating sporadically in all directions, and the longer it takes for the particle to travel the same distance when a force is applied, affecting the particle's initial velocity.

 

Not only will this cause the particle to curve towards the body of particles, but the effect of this phenomenon accumulates exponentially (as the closer it gets to the body of massive particles due to curving towards it, the more its Zitterbewegung will increase from interacting with electromagnetic radiation from the body of massive particles), causing the particle to accelerate.

 

If curved space-time were the only factor involved in gravitation, it is a mystery how free-fall can be initiated when an object is at rest relative to the source of the gravity, since in order for curved space-time to produce something resembling gravitation by itself, the object has to be moving.

 

Light takes longer to travel through a medium of massive particles because it ricochets off particles in the medium, causing its path to no longer be a perfectly straight line and therefore making its travel time in one direction longer. When light is being 'held up' in its travel time when passing through a group of massive particles (or in the case of denser groups or 'bodies' of massive particles, like planets and stars, the light is absorbed and slowly disperses from the group/body of particles in many directions), the light is being diffracted by the medium (although for denser groups of particles, 'diffracted' might not be the most appropriate term), which causes the radiation to contribute to the Zitterbewegung (German for trembling motion) of any particles it interacts with.

 

This Zitterbewegung, assuming it is being experienced in all directions by a particle, affects the particles velocity in the same way as curved space-time traditionally does in General Relativity; simply speaking, it causes the particles trajectory to curve and causes the particle to slow down in the direction of the body/group of massive particles, which is essentially the same as time-dilation described in the philosophy behind General Relativity, in that it takes a longer time for the same amount of force to make an object/particle travel a certain distance (but from the reference point of the object/particle of course, it traveled the normal distance one would expect to travel during an increment of time from the force applied, as there is no noticeable change in the passage of time locally).

 

The closer it gets to the group of massive particles, the more Zitterebewegung-inducing radiation it will encounter, causing it to move sporadically even more (and also mitigating its initial velocity even more as well); while the particle is vibrating, any instance where it vibrates in the direction of the body of massive particles, it will experience Zitterbewegung even more - which means the effect is self-sustaining and self-initiating, which is what we would expect with free-fall.

 

Does this part of my original post explain where the force behind the gravitational constant comes from?

Like, GR doesn't tell you where gravitational attraction comes from, it just shrugs its shoulders and throws in the gravitational constant just like Newtonian gravity.

 

Let's get this straight: GR solves two major problems with Newtonian gravity:

1. It describes gravity so it doesn't violate special relativity.

2. It describes how light is affected by gravity by following the geodesics in curved space-time (I'll just give up on this point; I can't remember why I thought it wasn't true anymore)

 

But although GR is an improvement on the Newtonian theory of gravity, it still doesn't tell us what the force of gravity actually is or where it comes from.... Did I just.. by chance explain where it comes from? Increasing Zitterbewegung of a particle as it approaches a massive object - with the Zitterbewegung being the result of loose radiation diffracted by the massive object hitting the particle in different directions?

Makes sense doesn't it? Am I a genius?

Edited June 25, 2015 by metacogitans

[Mordred]

Perhaps you should take the above EFE and look at the principle of least action. Null geodesic is the shortest time like path.

 

[latex]ds^2=0[/latex]

 

 

http://www.physics.usyd.edu.au/~luke/research/masters-geodesics.pdf

 

The above article has a decent coverage

Makes sense doesn't it? Am I a genius?

A true genius would post the mathematics. Of his theory, All I've read is that your not understanding what a null geodesic entails.

 

 

For example a null geodesic has the following properties. Only particles travelling at c can follow a null geodesic.

 

take the geodesic equation in 3+1 4 momentum form of particle P,

 

[latex]p^\alpha[/latex] is the 4-momentum.

 

[latex]p^\alpha=E(\eta^\alpha+V^\alpha)[/latex] with [latex]\eta^\mu V^\mu=0[/latex]

 

 

For a massless P (photon)

[latex]p_\mu p^\mu=0[/latex]

[latex]\eta_\mu \eta^\mu=-1[/latex]

[latex]V_\mu V^\mu=V_I V^I=1[/latex]

 

the above meaning photons travel at c with respect to [latex]O_e[/latex](Eularian observer) the above is a 4 momentum on a null geodesic.

 

 

 

Massive particles however has the following

 

[latex]m=\sqrt{p_\mu p^\mu}[/latex]

 

[latex]p_\mu p^\mu<0[/latex]

[latex]V_i V^i<1[/latex] a massive particle can never reach c and follows a time like geodesic.

 

So how does your idea mathematically describe the above?. How does it explain the invariance of c to all observer's?

 

The other problem is your not understanding the stress energy tensor.

 

See equations 1.1 of the article I posted.

Edited June 25, 2015 by Mordred

[swansont]

I am not posting my own alternative theory. I repeat, I am not posting my own alternative theory. If I was posting an alternative theory, the equation would have to be different, but the math is exactly the same, I'm still using the field equations in GR

 

!

Moderator Note

No, this is not true.

[Strange]

This is mathematically identitcal to the 'spacetime' curvature in a gravity well described by the tensors in the Einstein Field Equations

 

Can you prove (mathematically) that this is the case?

 

This is a common claim made by people with their own personal theories. Oddly, none of them are able to come up with a proof. I hope you are different.

[md65536]

One thing I was thinking is that light could follow the geodesics in curved spacetime described by GR, but is not subject to gravitational attraction (light won't enter free fall or accelerate exponentially due to gravity) since light is massless.

Yes, that's basically in agreement with GR. The bending of light is not a gravitational attraction pulling light off a straight path. The null geodesic "is" a straight path through curved spacetime. Light only bends along with the curvature of spacetime, and no more.

 

For example with a black hole it is not gravity pulling on the light particles that prevent their escape. It is the curvature of spacetime that makes all paths (all "straight lines") within the event horizon curve toward the singularity. (That, and the coordinate speed of light is 0 at the event horizon according to a distant observer.)

Edited June 25, 2015 by md65536