Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: sciencepm on 12/02/2021 07:55:55
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Hi everybody,
sorry I’m not a space expert…
I’ve read that light is bent when it passes a massive body in the space. Why does this happen?
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Should the question be 'why does a massive body bend spacetime'?
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We were always taught that light travels in straight lines.
Draw a straight line on a sheet of paper. Then curve the paper a little. Now the line is cured (bent) but still moving In a straight line.
Conclusion is that space has curved.
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There are two ways of looking at it. One way is the way that lunar7 has described (that the path of light is deflected because the space around a massive body is distorted. This is the explanation by general relativity). The other is that light is attracted to the gravitational field of the massive body and is therefore pulled towards it. Both explanations are equally correct.
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The effect of starlight being bent when it passed close to the Sun was one of the first experimental verifications of Einstein's General Relativity. It led to considerable fame for Einstein.
- The test was conducted by two teams of astronomers, led by Arthur Eddington, who took pictures of the positions of stars during a total solar eclipse, in 1919. This was compared with the positions of these stars at a different time of the year, when their light path passed nowhere near the Sun.
Einstein described the effect of mass as that of curving spacetime.
- Light tends to take the shortest path between two points.
- But when spacetime is curved, the shortest path is also curved.
Alternatively, you could informally imagine this effect as follows:
- Light can be viewed as particles of light (photons) which carry energy, and have an equivalent mass. The Sun "attracts" the passing photons, bending their path. This concept was compatible with Isaac Newton's theory of gravity, but the bending is twice as great as Newton's theory would predict.
- According to General Relativity, near a massive object, time slows down. This means that light slows down (as seen by a distant observer). Light can be viewed as waves of light, and when waves pass into a medium which has a different speed (eg light waves into a lens, or ocean waves near the shore), the path of the wave is bent; this is now called gravitational lensing.
See: https://en.wikipedia.org/wiki/Eddington_experiment
https://en.wikipedia.org/wiki/Gravitational_lens
Oops! crossover with Kryptid...
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We were always taught that light travels in straight lines.
Draw a straight line on a sheet of paper. Then curve the paper a little. Now the line is cured (bent) but still moving In a straight line.
Conclusion is that space has curved.
No. The conclusion is that the sheet of paper has curved. The space around it, hasn't curved at all
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No. The conclusion is that the sheet of paper has curved. The space around it, hasn't curved at all
It's an analogy.
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No. The conclusion is that the sheet of paper has curved. The space around it, hasn't curved at all
It's an analogy.
You mean, it's just a fanciful comparison. Not real. I agree.
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The curvature of space is real. It can be measured.
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The curvature of space is real. It can be measured.
How can it be measured. If space is really curved, then wouldn't everything in it be curved as well.
Such as rulers. All rulers would be curved. So wouldn't they give the same measurements, as flat rulers in flat space?
How would you be able to tell the difference?
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How can it be measured.
By measuring things like gravitational lensing.
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The geometry of curved space is different from that of flat, Euclidean space. That leads to different physical consequences, such as the anomalous orbital precession of Mercury. General relativity makes precise, quantitative predictions based on gravity being a distortion of space-time, resulting in predictions such as the geodetic effect (which has been measured and found to align with the predictions of general relativity by Gravity Probe B).
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How can it be measured.
By measuring things like gravitational lensing.
The gravitational lensing effect merely shows that particles of light - photons, are affected by gravitational fields.
As are all particles. What's that got to do with curvature of space? Photons passing through the gravitational field of a massive object such as a star, will naturally get deflected. By the star. Not by any "curvature of space".
So how does gravitational lensing improve the case for a supposed " curving of space"?
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The geometry of curved space is different from that of flat, Euclidean space. That leads to different physical consequences, such as the anomalous orbital precession of Mercury. General relativity makes precise, quantitative predictions based on gravity being a distortion of space-time, resulting in predictions such as the geodetic effect (which has been measured and found to align with the predictions of general relativity by Gravity Probe B).
The anomalous precession of Mercury might be explained in other ways. Bear in mind, that no anomalous effects have been detected in the orbit of Venus, or the Earth. Both planets are close to the Sun, like Mercury, and might be expected to display similar effects. But none have been found necessary to invoke GR..
Probably, the GR effect is a red herring.
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Actually, that's not true. The Newtonian view of gravitational lensing predicts a different value of path distortion than the relativistic view does (by half, to be precise). The relativistic model is the one that measurements support.
You're wrong about anomalous orbital precession not affecting Venus or Earth. It's just smaller than for Mercury because they are more distant. You're also going to need to explain why general relativity predicts the correct mathematical value if it's wrong. Do you think Einstein just got very lucky?
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Do you think Einstein just got very lucky?
I think he got lucky by applying his ideas to the Solar System. There his results, can by fudging, be made to seem plausible. Especially in explaining anomalies in Mercury's orbit. Good case.
But what happens when his ideas are applied to the wider Universe? Such as the Galaxies.
The anomalous rotation of galaxies cannot be explained by Einstein's theory. It's a complete failure.
So much so, that present-day astrophysicists have had to resort to inventing a completely new form of matter:
"Dark Matter". This is something that you can't see. But is there, apparently. With no observational evidence of its
physical existence
Not to mention "Dark Energy". This at least has some recourse to Einstein's idea of the "Cosmological Constant"
But these ideas are probably wild-goose chases. Which will laughed at in 2050.
In the meantime. let's just take it all with a pinch of salt
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But what happens when his ideas are applied to the wider Universe? Such as the Galaxies.
They still work.
That's the cool thing about science.
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How can it be measured.
One way is to measure (with a tape measure) the diameter of Earth, and then its circumference. This isn't practical of course since you can't pass a tape measure through Earth, and it is hard to line up if held off to the side, but if you did, the circumference would definitely be less than the diameter * π. This can only be explained with non-Euclidean spacetime, and is quantified precisely by Einstein's field equations.
The difference isn't much with Earth, but it is for more massive things like neutron stars.
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How can it be measured.
One way is to measure (with a tape measure) the diameter of Earth, and then its circumference. This isn't practical of course since you can't pass a tape measure through Earth, and it is hard to line up if held off to the side, but if you did, the circumference would definitely be less than the diameter * π. This can only be explained with non-Euclidean spacetime, and is quantified precisely by Einstein's field e
Surely the tape-measure would have to be pulled out by using energy, which would increase its mass, thereby making it expand, so it would give the measurement when it was looked at?
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Surely the tape-measure would have to be pulled out by using energy, which would increase its mass, thereby making it expand, so it would give the measurement when it was looked at?
You're attenpting to nitpick your way out of the point of the argument.
A tape measure already on the surface of Earth would not require energy to wrap around the circumference. The one measuring the diameter would actually lose a bit of energy due to the drop in PE of part of it, but that wouldn't affect its proper length. Proper length is a frame invariant quantity, while mass and energy are not.
For the sake of argument, we'll assume no thermal difference in the tape since that actually does change the length of most materials, and far more than this relativistic length change that you suggest. For control purposes, we'll measure a cold hard perfectly spherical rock the size of Earth that has no problem with a hole being drilled through which the tape measure can be passed.
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We bowed a flashlight beam thru sugar water, in 8th grade. An example of the affects of a density gradient.
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I think he got lucky by applying his ideas to the Solar System. There his results, can by fudging, be made to seem plausible.
Please supply a reference for where "fudging" was used in order to make his predictions match reality.
The anomalous rotation of galaxies cannot be explained by Einstein's theory. It's a complete failure.
That's not the same thing as anomalous orbital precession. At all.
which would increase its mass, thereby making it expand,
Then wait for it to cool down afterwards. Or use something that doesn't experience thermal expansion (like a laser beam).
We bowed a flashlight beam thru sugar water, in 8th grade. An example of the affects of a density gradient.
That's a different phenomenon.
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his results, can by fudging, be made to seem plausible
It is true that the size of Mecury's precession was known at the time of Einstein, and he calculated what the answer was before he published his theory of General Relativity (GR).
But the mathematical basis of GR has been extremely successful for over a century - even when Einstein himself didn't believe it was possible.
The equations of GR allow for:
- An expanding universe, which Einstein himself didn't believe, and even tried to eliminate the possibility - until the reality was discovered by Hubble
- Black holes, which Einstein himself initially didn't believe. Penrose recently got the Nobel prize for showing that they were likely to form in supernova explosions, and now we have an image of a supermassive black hole in the center of a nearby galaxy
- Gravitational waves, which Einstein didn't think we would be able to detect - and now we have sound recordings of black holes colliding
- So it wasn't a matter of Einstein "fudging" the results - the mathematics produced results which Einstein himself did not believe.
There are many other experimental verifications, see: https://en.wikipedia.org/wiki/Tests_of_general_relativity
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How can it be measured.
One way is to measure (with a tape measure) the diameter of Earth, and then its circumference. This isn't practical of course since you can't pass a tape measure through Earth, and it is hard to line up if held off to the side, but if you did, the circumference would definitely be less than the diameter * π. This can only be explained with non-Euclidean spacetime, and is quantified precisely by Einstein's field equations.
The difference isn't much with Earth, but it is for more massive things like neutron stars.
Actually, I'm sure the size of the Earth can me measured during a lunar eclipse, when the Earth's shadow is cast on the Moon. Due to the vast distances it can be assumed the rays are parallel.
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How can it be measured.
One way is to measure (with a tape measure) the diameter of Earth, and then its circumference. This isn't practical of course since you can't pass a tape measure through Earth, and it is hard to line up if held off to the side, but if you did, the circumference would definitely be less than the diameter * π. This can only be explained with non-Euclidean spacetime, and is quantified precisely by Einstein's field equations.
The difference isn't much with Earth, but it is for more massive things like neutron stars.
Actually, I'm sure the size of the Earth can me measured during a lunar eclipse, when the Earth's shadow is cast on the Moon. Due to the vast distances it can be assumed the rays are parallel.
Nowhere near to the accuracy needed to note the effects discussed. In this case "nearly parallel" isn't good enough, especially when combined with the fact that the Sun isn't a perfect point source, which means the edge of the shadow it casts will be a bit fuzzy.
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Gravitational mass bend space-time not space.
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Light is electro-magnetic and as such could be bent if a voltage field attracted it or much more likely, if a magnetic field tried to magnetically spin the light beam .Cannot see that gravitation has anything to do with the deflection of light as the beam is totally mass-less?
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Photons have an inertial mass and a delayed gravitational mass. Gravitational perturbations travel at the speed of light. What we call massive particles cannot reach the speed of light. For a photon, its gravitational mass is totally redshifted in its direction of motion. That's why light bends twice as much as massive particles, because it has no massive counter field in its direction of motion.
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Cannot see that gravitation has anything to do with the deflection of light as the beam is totally mass-less?
You are intermixing 2 different physics models here; Newtonian and Relativity.
Under Newton, gravity is an attraction between masses, using the Newtonian definition for mass.
With Relativity, gravity is coupled to the Energy momentum tensor, of which the Newtonian concept of "mass" is only a single component.
Classical Newtonian mass is what Relativity would call rest or Proper mass.
Thus when it is said that light is massless, we means it has no proper mass. However, it still has energy, momentum* etc, which are other components of the energy-momentum tensor through gravity couples.
So under Newton, gravity only relies on the "mass", while under Relativity energy content also plays a role.
The point is that you can't use the gravity model and definition of "mass" from one theory and expect it to make sense if you apply it to a theory that uses a different model.
* and while the Newtonian definition of momentum is p= mv, momentum of a photon is related to its energy by p = E/c
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HI All
There are two ways of looking at it. One way is the way that lunar7 has described (that the path of light is deflected because the space around a massive body is distorted. This is the explanation by general relativity). The other is that light is attracted to the gravitational field of the massive body and is therefore pulled towards it. Both explanations are equally correct.
Janus states
So under Newton, gravity only relies on the "mass", while under Relativity energy content also plays a role.
The point is that you can't use the gravity model and definition of "mass" from one theory and expect it to make sense if you apply it to a theory that uses a different model.
* and while the Newtonian definition of momentum is p= mv, momentum of a photon is related to its energy by p = E/c
So if we use Kryptids excellent point of gravity pulling towards I believe Janus the aspect that links the two definitions is Energy as you state, ie the energy potential of a gravitational field as is demonstrated in the Harvard tower experiment.
https://en.wikipedia.org/wiki/Pound%E2%80%93Rebka_experiment
for example I believe you can link the time dilation delta for the height of the tower (bottom - top or vice versa) to the gravitational potential accounting for the red/blue shift of light .
And gives exactly the same as using the velocity time dilation equation if you dropped and object from said height and plugged in velocity reached (ignoring friction) over that distance in that acceleration field into velocity time dilation equation.
So I believe you could calculate some aspects of what's under consideration using things as simple as suvat equations and they wouldn't be contradictory.
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I think (Einstein) got lucky by applying his ideas to the Solar System. There his results, can by fudging, be made to seem plausible.
I would add that the accelerating expansion of the universe was only discovered in the 1990s, so Einstein was totally unaware of it
- It applies to objects far outside our Solar System (and would not be measurable on the scale of our galaxy, let alone our Solar System)
- And yet, it seems that Einstein's mathematical model of General Relativity is the best model we have for it, with the expanding set of measurements we are continually adding
I don't think the mathematical model was "lucky" or "fudged" - it just followed the evidence
- The part where Einstein did find out he had fudged the result was in picking a value for the cosmological constant to fit in with the common view at the time (stretching all the way back to Newton, and probably to Greek philosophers) that the universe as a whole (outside the Earth & Planets) was static and unchanging.
So, when you say (in another thread) that "I don’t understand physics: does anyone understand physics these days?", are you accepting the expansion of the universe, or are you staying with the ancient philosophers?
- And are you accepting the accelerating expansion of the universe, or are you staying with Hubble?
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I don't think the mathematical model was "lucky" or "fudged" - it just followed the evidence
- The part where Einstein did find out he had fudged the result was in picking a value for the cosmological constant to fit in with the common view at the time (stretching all the way back to Newton, and probably to Greek philosophers) that the universe as a whole (outside the Earth & Planets) was static and unchanging.
A couple of points. Einstein tended to approach things a bit differently that other theorists. While they would start from the experimental evidence and work back to a theory to explain it, he tended to start from basic concepts and assumptions, follow them to their logical conclusion and see if it matched the evidence. Pretty much the opposite of "fudging".
The other thing to consider with his cosmological constant was that, at the time, he developed GR, it still had not been established that the universe extended past the Milky way. So not only did he not know of the expansion, but he was considering a much smaller "universe".
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Einstein also did not know that gravitation could not balance the universe; or that dark matter and dark energy had to be invented to try to explain the WMAP results.
But if the universe is magnetised and polarised then because of the magnoflux spin effect most of the forces that operate inside galaxies can be explained.
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We bowed a flashlight beam thru sugar water, in 8th grade. An example of the affects of a density gradient.
Yes. Though I'm not quite sure why "sugar water", whatever that it is, was employed in the experiment
Wouldn't a glass of plain water, exhibit the same effect? I'm thinking of the well-known phenomenon of a drinking-straw placed in a glass of water.
The straw then looks bent. This is a purely optical effect. Caused by refraction of light through the different "density gradients", as you put it, of water and air.
Is the "bending" caused by any enormous differences in the mass of the three substances involved - water, glass, and air. Surely not. The mass of a glass of water is minuscule. The air even less.
Yet somehow, they can cause a beam of photons to exhibit a startling deviation, and cause a straight straw appear bent.
I think simple observations such as this, may suggest that caution needs to be exerted, when interpreting "lensing" effects observed among distant galaxies.
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Yes. Though I'm not quite sure why "sugar water", whatever that it is, was employed in the experiment
So, you fundamentally fail to understand the whole thing...
Wouldn't it have been better to stop at that point, and ask?
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I could look up what sugar-water is, but decline to do, as it doesn't seem of any real relevance.
The point I was making is this: refraction of light through the lens-shaped dust clouds which surround distant galaxies, could explain the image displacement effects which we observe from Earth.
How can you confute this reasonable suggestion. When even a glass of water, observed at close quarters, can make a straw look bent, when it actually isn't. I rest my case.
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it doesn't seem of any real relevance.
It doesn't "seem" that way to you, but you don't know what you are talking about.
So your approach is to carry on with your own special brand of ignorance.
Why would you do that?How can you confute this reasonable suggestion.
Chromatic aberration.
Also, dust doesn't diffract light, it scatters it.
Did you really think that science hadn't already thought of that?
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You accuse me for being an ignorant person. That's a charge I never heard before.
I probably have a wider range of knowledge, across all fields, than anyone else on this forum.
But mere knowledge, by itself, is not enough to gain insight into truth. Only constant questioning can do that.
That's why I ask questions. Sometimes the answers on here provide new insights. For which I'm grateful.
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You accuse me for being an ignorant person.
It's not an accusation; it's an observation.
YThat's a charge I never heard before.
I find that hard to believe.
That's why I ask questions.
No, even when it's obvious that you would gain from asking a question, you choose not to.
I could look up what sugar-water is, but decline to do, as it doesn't seem of any real relevance.
Because you are ignorant of the importance of the answer.
But mere knowledge, by itself, is not enough to gain insight into truth.
The lack of knowledge isn't much of a path to truth either, is it?
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I could look up what sugar-water is, but decline to do, as it doesn't seem of any real relevance.
The point I was making is this: refraction of light through the lens-shaped dust clouds which surround distant galaxies, could explain the image displacement effects which we observe from Earth.
How can you confute this reasonable suggestion. When even a glass of water, observed at close quarters, can make a straw look bent, when it actually isn't. I rest my case.
And if you look really close at that pencil, you will not a fuzzy rainbow effect at its edges. This is the chromatic aberration that Bored Chemist brought up. When light is refracted or even scattered, different frequencies of light have their paths altered by different amounts (This is why a prism can break white light up into is component colors.)
The fact that light passing by galaxies shows no sign of this effect indicates that refraction or scattering cannot be the cause.
And to reiterate Bored Chemist's remark: Why do you think that scientists wouldn't have ruled out already known effect before coming to the to the conclusion they did?
If you thought of it with your limited grasp of science, why wouldn't had they?
What is it that makes you think that the professional scientists that study these things are so incompetent that hey couldn't find their backside with both hands?
Why do you think that you can see things they can't?
The only reason I can come up with is misplaced hubris on your part.
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The point I was making is this: refraction of light through the lens-shaped dust clouds which surround distant galaxies, could explain the image displacement effects which we observe from Earth.
There is no such lens-shaped dust cloud around the Sun, so that can't be the explanation for the observed deflection of light around it. Einstein predicted the correct value for gravitational lensing before it was even measured, so "fudging the numbers" can't be invoked to explain how he got it right.
I probably have a wider range of knowledge, across all fields, than anyone else on this forum.
Even if that was true, that doesn't make you right about everything. In this particular case, there is strong evidence that you are wrong.
How about I show the actual math? The equation for gravitational lensing as predicted by general relativity is as follows:
α = (4GM)/(c2r), where
α = angle of deflection,
G = the gravitational constant
M = the mass of the object in question,
c = the speed of light, and
r = the distance at which the lensing is measured
So we put in the parameters for the Sun:
α = (4GM)/(c2r)
α = (4 x (6.674 x 10−11 m3⋅kg−1⋅s−2) x (1.9885 x 1030 kg))/((299,792,458 m/s)2) x (695,700,000 m))
α = ((2.669 x 10-10) x (1.9885 x 1030))/((299,792,458)2) x (695,700,000))
α = (5.3084996 x 1020)/((299,792,458)2) x (695,700,000))
α = (5.3084996 x 1020)/((8.9875518 x 1016) x (695,700,000))
α = (5.3084996 x 1020)/(6.2526398 x 1025)
α = 0.00000849001 radians (1.75119 arc-seconds)
The original observations testing gravitational lensing back in 1919 measured deflections of 1.98+0.16 and 1.61+0.3 arc-seconds. That puts an experimental range of 1.31 to 2.14 arc-seconds, which the predicted result is very close to the middle of. The Newtonian prediction of 0.85 arc-seconds is well outside of the experimentally-determined range. Since then, Einstein's prediction has been confirmed to within 0.02%.
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There are several ways to "bend" something. One change in direction can be a bend.....so a bounce can be called a bend. A sequential series of bounces, can also be called a bend.
And a continuous change in direction can be called a bend. I call it a bow, to tell the difference between them. These are different dynamics. Different motions.
I have never liked the term bend.....when it comes to a straw in water. I think of it as a displaced reflection.
Plain water at equal temp, has the same density. At least, in an aquarium. The sugar gives the water a density gradient with the same temp. This density gradient does not bounce......it continuously bows the light.
Do you believe that the atmosphere of the sun has a density gradient? It's a plasma gradient. We are not very familiar with plasma gradients......like other gradients, because plasma is reactive. It's not neutral. I expect the bow to be different with a reactive gradient. A twist in polarity might easily cause a bow.
Do you think that there could be a plasma gradient around a galaxy?
Do our galaxy bubbles have a density gradient?
Evidence is subjective, that's why we have so much of it.
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Evidence is subjective
No, it isn't.
Do you believe that the atmosphere of the sun has a density gradient?
It does, but the evidence doesn't match up with that being the cause of gravitational lensing (as pointed out before),
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I have never liked the term bend.....when it comes to a straw in water. I think of it as a displaced reflection.
Plain water at equal temp, has the same density. At least, in an aquarium. The sugar gives the water a density gradient with the same temp. This density gradient does not bounce......it continuously bows the light.
Do our galaxy bubbles have a density gradient?
It isn't reflected.
Can we stop talking about density?; the parameter that matters is the refractive index.
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I am also no big expert on this topic. Just an enthusiast as to how everything in life works. Furhtermore trying to just seek out a logical explanation for almost everything in life ;D
I recall seeing in a couple of videos on YouTube that light ist bent by objects.
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I am also no big expert on this topic. Just an enthusiast as to how everything in life works. Furhtermore trying to just seek out a logical explanation for almost everything in life ;D
I recall seeing in a couple of videos on YouTube that light ist bent by objects.
Is or isn't?
also, one needs to be careful when getting information from YouTube videos, as there is a lot of incorrect information out there.
as far as light direction being changed by objects. There are a few ways this can happen:
Reflection. Light bounces off the object.
Scattering. light is effected by passing through an object or medium by interacting with the individual particles within it.
Refraction, The light path direction is changed by passing through the boundary between mediums of different refraction indices. (or through a medium with a changing index of refraction.
Defraction. Light path is spread by passing through a slit or close to the edge of an object
With all of these, with the exception of reflection, the degree of path change is dependent on the wavelength of the light.
Thus, they would produce a measurable separation of the component colors in white light.
With gravitational lensing, you would not see such a separation of colors. The path of all frequencies would be changed equally.
This is where all these alternate explanations for the bending of light as they pass the Sun or distant galaxies fail. These other suggested mechanisms would produce other noticeable effects in the light that we just don't observe. *
* Plus, in the example of our own Sun, it would be take the greatest of coincidences for these effects to cause the exact amount of bending as predicted for gravitational lensing.
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When we bowed light, we did not have lasers. We used a flashlight. White light. Bowed white light. Full of phase and wavelength.
What term do you use to describe the path of light.......that passes into a WIDE boundary interface......AND...... that wide interface has a density gradient?
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When we bowed light, we did not have lasers. We used a flashlight. White light. Bowed white light. Full of phase and wavelength.
What term do you use to describe the path of light.......that passes into a WIDE boundary interface......AND...... that wide interface has a density gradient?
GRIN
https://en.wikipedia.org/wiki/Gradient-index_optics
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I am also no big expert on this topic. Just an enthusiast as to how everything in life works. Furhtermore trying to just seek out a logical explanation for almost everything in life ;D
I recall seeing in a couple of videos on YouTube that light ist bent by objects.
Is or isn't?
also, one needs to be careful when getting information from YouTube videos, as there is a lot of incorrect information out there.
as far as light direction being changed by objects. There are a few ways this can happen:
Reflection. Light bounces off the object.
Scattering. light is effected by passing through an object or medium by interacting with the individual particles within it.
Refraction, The light path direction is changed by passing through the boundary between mediums of different refraction indices. (or through a medium with a changing index of refraction.
Defraction. Light path is spread by passing through a slit or close to the edge of an object
With all of these, with the exception of reflection, the degree of path change is dependent on the wavelength of the light.
Thus, they would produce a measurable separation of the component colors in white light.
With gravitational lensing, you would not see such a separation of colors. The path of all frequencies would be changed equally.
This is where all these alternate explanations for the bending of light as they pass the Sun or distant galaxies fail. These other suggested mechanisms would produce other noticeable effects in the light that we just don't observe. *
* Plus, in the example of our own Sun, it would be take the greatest of coincidences for these effects to cause the exact amount of bending as predicted for gravitational lensing.
Thank you for the heads up!!
That does shed some light on this topic ;D ;D
About the YouTube stuff: Yeah, I know... a lot of Information is kind of meh and not percise. I tend to watch VSauce a lot. Their channels seems to be trustworthy. At least I don`t recall getting any shady/false Informations from there.
Maybe someone could recommend other trustworthy YouTbe channels? Love to spend some of my free time like that.
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When we bowed light, we did not have lasers. We used a flashlight. White light. Bowed white light. Full of phase and wavelength.
And, if you had looked closely at the edges of that bowed wide light, you would have seen colored fringes caused by chromatic aberration, where the different wavelengths that make up "white" light where bowed by differing amounts.
You won't see it in the main beam because the all the different colors are still there and mixing, which it why it is only noticeable at the edges.
However, when looking at something like the light of a star bending as it passes the Sun, it doesn't act like a broad beam, but like a point source, and the chromatic aberration would be more noticeable if the bending was caused by interaction with a medium.