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Author Topic:   Gravity vs. Light
CrackerJack
Inactive Member


Message 1 of 18 (93981)
03-22-2004 8:38 PM


What is the attraction effect of gravity on light? There are three possibilities. Either light is attracted to mass by means of gravity, or it is repelled by mass, or there is no effect. But almost all scientists say that light, like any other particle is attracted to mass. For example, if you have a black hole, light and matter is sucked into the black hole, but no light can escape because of the enormous gravitational pull. So if light is travelling in the vicinity of a body of mass, what effect will this attraction have on the light? I see two possibilities. Either gravity will cause the light to speed up/slow down, depending on the light's direction with respect to the gravitational pull, or the light will be stretched out. Being that we are told that light moves at a constant speed, this only leaves the option of light being stretched. It would not matter which direction the gravitational pull is coming from. All gravitational pull from all directions would stretch the light out. If an object is trying to move at a constant rate, and a force is pulling at it from behind, or pulling at it from the front, the net effect will be the same. In order to maintain it's desired speed, pressure will be put on it to stretch out in order to counteract the pulling force. So if I am correct in my assumptions, it means that all light between stationary objects will tend to be red shifted due to gravity, and the amount of red shift will increase as the distance travelled ("age") increases. Assuming a homogeneous universe, the stretching effect could be calculated, but if the light travelled in a non-homogeneous area of space where the gravitational pull was stronger or less, then the effect could not be calculated unless the gravitational pull was known for each region of space the light travelled through.
So, if gravity is affecting the red shift of light in this manner, then the cause of the high red shifts of distant galaxies may be due to gravity and thus there is no proof that the universe is expanding.

Replies to this message:
 Message 3 by JonF, posted 03-22-2004 9:18 PM CrackerJack has replied

  
V-Bird
Member (Idle past 5585 days)
Posts: 211
From: Great Britain
Joined: 03-22-2004


Message 2 of 18 (93984)
03-22-2004 8:51 PM


Gravity is one of the four fundemental forces, it is 'part of' not separate to energy, the four forces are 'within' energy, so it is found to be concentrated where ever there is a concentration of energy, matter is in fact energy that has been acted upon by these four forces, they are like brothers linked inextricably together, gravity tho is the most pervasive of them all and so its effects are fellt across the entire universe.
[This message has been edited by V-Bird, 03-22-2004]

  
JonF
Member (Idle past 168 days)
Posts: 6174
Joined: 06-23-2003


Message 3 of 18 (93987)
03-22-2004 9:18 PM
Reply to: Message 1 by CrackerJack
03-22-2004 8:38 PM


So if I am correct in my assumptions, it means that all light between stationary objects will tend to be red shifted due to gravity
You are not correct in your assumptions. Your hypothesis is known as the "tired light" hypothesis; it was tested and it failed the tests. It doesn't happen. Gravity does indeed affect light (crudely put, light has energy, energy is mass by E = mc2, therefore gravity affects light) but light is not a physical thing that can be stretched or compressed like a spring. Changing wavelength is changing energy, not physical size. Gravity does change the wavelength of light under some circumstances, but not in the manner that you propose.
For more discussion of tired light see Errors in Tired Light Cosmology.

This message is a reply to:
 Message 1 by CrackerJack, posted 03-22-2004 8:38 PM CrackerJack has replied

Replies to this message:
 Message 4 by CrackerJack, posted 03-23-2004 12:07 AM JonF has not replied

  
CrackerJack
Inactive Member


Message 4 of 18 (94008)
03-23-2004 12:07 AM
Reply to: Message 3 by JonF
03-22-2004 9:18 PM


No, I'm not referring to "Tired Light". I've done a little more research on this since I posted that and found that what I was trying to express is called the Shapiro Effect and it has evidently been proven to exist. See http://www.geocities.com/newastronomy/Shapiro.htm for more information on this. I am no physicist, so perhaps my thoughts and words to express those thoughts were not exactly perfect. I will try to research more about the Shapiro Effect and see what experiments have been done to prove or disprove if its effects could be enough to accont for all the redshift we are seeing.

This message is a reply to:
 Message 3 by JonF, posted 03-22-2004 9:18 PM JonF has not replied

Replies to this message:
 Message 5 by RAZD, posted 03-23-2004 1:16 AM CrackerJack has replied
 Message 6 by Darwin Storm, posted 03-23-2004 1:29 AM CrackerJack has replied

  
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 5 of 18 (94012)
03-23-2004 1:16 AM
Reply to: Message 4 by CrackerJack
03-23-2004 12:07 AM


red light
The speed of light is not changed, what changes is the frequency\wavelength. In the black hole scenario the light is not stopped so much as it is just not allowed to get out of an orbit that gets beyond the "event horizon" which also involves massive time dilation for an outside observer (it's that relativity thing -- the time would not appear slowed to the light particle). The gravity effect cannot keep stretching light wavelengths with distance as the effect of gravity drops off as the square of the distance, the best fit is the Doppler effect. Another thing to consider is that there are also particles that have mass and which are associated with certain events (supernovas etc) and which are detected at the times associated with the light from those events -- a correlation of phenomena which should not happen if gravity were the cause of the red shift.

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist

This message is a reply to:
 Message 4 by CrackerJack, posted 03-23-2004 12:07 AM CrackerJack has replied

Replies to this message:
 Message 8 by CrackerJack, posted 03-23-2004 6:02 AM RAZD has replied

  
Darwin Storm
Inactive Member


Message 6 of 18 (94017)
03-23-2004 1:29 AM
Reply to: Message 4 by CrackerJack
03-23-2004 12:07 AM


The supposed Shapiro effect also violates the first postulate of special realitivity, that simply states that the speedo of light is the same for all observers, regardless of their motion realitive to the source of the light.

This message is a reply to:
 Message 4 by CrackerJack, posted 03-23-2004 12:07 AM CrackerJack has replied

Replies to this message:
 Message 7 by RAZD, posted 03-23-2004 1:45 AM Darwin Storm has not replied
 Message 9 by CrackerJack, posted 03-23-2004 6:17 AM Darwin Storm has not replied

  
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 7 of 18 (94021)
03-23-2004 1:45 AM
Reply to: Message 6 by Darwin Storm
03-23-2004 1:29 AM


but it is a postulate and not a fact ...

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist

This message is a reply to:
 Message 6 by Darwin Storm, posted 03-23-2004 1:29 AM Darwin Storm has not replied

  
CrackerJack
Inactive Member


Message 8 of 18 (94062)
03-23-2004 6:02 AM
Reply to: Message 5 by RAZD
03-23-2004 1:16 AM


Re: red light
Well, according to the website, the gravitational pull due to the Shapiro Effect decreases with the inverse of the logarithm of distance, not the inverse of the distance. And this has supposedly already been verified by observations of the Mariner spacecrafts. If true, it would mean that gravity would still have an effect even at much greater distances.
I don't quite see your point about the correlation of time for particles with mass and the light. The gravity is affecting the light after it has left the emitter and continues to affect it as it travels through empty space, just as the expansion of the BBT is affecting the light as it travels through space. Neither of these effects on the redshift have anything to do with the light as it being emitted from the source. So I fail to see how you could distinguish which of these two possibilities caused the redshift based on particles being emitted by the supernova. The gravity strength of the source may affect the redshift slightly as the light is being emitted, but I would think this effect would be minimal and is not what the Shapiro Effect refers to. Any further information on this correlation or a link to a site falsifying the Shapiro Effect would be appreciated.
One more thing to consider, is that if the Shapiro Effect is something to be reckoned with, and if the BBT is also considered correct, then the Shapiro Effect could have a drastic effect on how we interpret certain observations. For instance, if we use the current estimates of the expansion rate as being correct, it would mean the universe is much younger than what most cosmologists say it is. Furthermore, any observations of events early in the formation of the universe would be even more profoundly influenced by gravity due to the universe being much more compact at that time and thus a much larger Shapiro Effect. So in this case, the whole model of the universe would likely fall apart because there wouldn't be enough time for the universe to develop as we see it. But, on the other hand, with the Shapiro Effect it would mean that the expansion rate could be much less to achieve the redshifts that we observe, and this would give us a much older universe.

This message is a reply to:
 Message 5 by RAZD, posted 03-23-2004 1:16 AM RAZD has replied

Replies to this message:
 Message 10 by RAZD, posted 03-23-2004 11:29 AM CrackerJack has not replied

  
CrackerJack
Inactive Member


Message 9 of 18 (94069)
03-23-2004 6:17 AM
Reply to: Message 6 by Darwin Storm
03-23-2004 1:29 AM


So if the Shapiro Effect is impossible, then gravity is not affecting the redshift of light. But doesn't that violate Einstein's Theory of Relativity where he observed that gravity does affect light when it leaves the surface of the source and causes loss of energy and thus a redshift? I find it hard to believe that gravity does not affect the light to at least some degree as it is travelling through space, the only question in my mind is how much. I will continue to try to research this and see if I can find some good verifiable data which shows how much of an effect it will cause.

This message is a reply to:
 Message 6 by Darwin Storm, posted 03-23-2004 1:29 AM Darwin Storm has not replied

  
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 10 of 18 (94120)
03-23-2004 11:29 AM
Reply to: Message 8 by CrackerJack
03-23-2004 6:02 AM


Re: red light pioneers
CrackerJack's reply
... the Shapiro Effect decreases with the inverse of the logarithm of distance, not the inverse of the distance. And this has supposedly already been verified by observations of the Mariner spacecrafts.
The effect on satellites Pioneer 10 and 11 would also be noticeable as they are the furthest craft from earth. In fact there is an anomaly in their oribits -- see Spacecraft anomalies put gravity to the test:
Indeed, the spacecraft move as if they were subject to a new, unknown force pointing towards the Sun. This force imparts the same constant acceleration, ap, of about {10e-7 cm/s/s} to all three spacecraft, about ten orders of magnitude less than the free-fall acceleration on Earth.
The third satellite mentioned is Ulysses - "on an elongated orbit that roughly bridges the orbits of Jupiter and Earth" -- Note that these satellites are outside the orbit of the earth while the Mariner satellites were inside earth's orbit (10 going to Mercury), and thus are much more relevant to any discussion of long distance effects of gravity.
Also see The Pioneer anomaly : a bulk scalar field ?
Authors considered the possibility that the origin of ap is:
  1. an effect of a modification of gravity like
    1. the addition of a Yukawa force to the Newtonian
    2. Milgrom’s proposed modification of gravity
  2. If the cause is dark matter (DM), consistency with the accuracy of the ephemeris implies an amount less than a few {10e-6 M} within the orbit of Neptune.
... ... ...
So, it may be of interest to look for new physics and try to make some predictions that can be tested in future missions (Pluto Express mission, Solar Probe mission).
As we have shown, a bulk scalar field external to gravity and which respects the WEP, may provide a solution to both the anomalous acceleration observed on remote spacecraft and the absence of a comparable effect on planets, comets or asteroids.
In other words we are talking about a measured gravity anomaly effect on the order of dark matter within our solar system, but not one sufficient to cause the Shapiro effect. That the same anomaly in gravity that gives rise to the concept of dark matter is observed within our solar system should be expected, as this is consistent with the standard model.
CrackerJack's reply
I don't quite see your point about the correlation of time for particles with mass and the light. The gravity is affecting the light after it has left the emitter and continues to affect it as it travels through empty space
The effect of gravity is proportional to the mass of the object, thus those with significant mass can be predicted to arrive later than those with little or none and you can chart out which particles should arrive in what order and at what relative intervals. The first to arrive are the light\radio waves, consistently with the intervals to the others predicted by their having 0 mass and 0 gravitational attraction. Remember that for relativity the effect of gravity on light is not from attraction of the light particle but from the warping of space by gravity about the objects with mass -- this is why the prediction of light being bent by gravity was a surprise and a confirmed surprise -- warping that includes time dilation effects and causes the space to act as a "gravitational" lens.
If the effect of gravity was as claimed by the Shapiro effect, then the intervals of the arrival of particles would be different than what is predicted by the standard model -- and what is observed (which does fit the standard model (and the ekpyrotic model)).
CrackerJack's reply
... if the Shapiro Effect is something to be reckoned with, and if the BBT is also considered correct, then the Shapiro Effect could have a drastic effect on how we interpret certain observations. For instance, if we use the current estimates of the expansion rate as being correct, it would mean the universe is much younger than what most cosmologists say it is.
It isn't.

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist

This message is a reply to:
 Message 8 by CrackerJack, posted 03-23-2004 6:02 AM CrackerJack has not replied

  
Eta_Carinae
Member (Idle past 4374 days)
Posts: 547
From: US
Joined: 11-15-2003


Message 11 of 18 (94124)
03-23-2004 12:06 PM


The Shapiro Effect
The Shapiro effect is a huge non sequitur here. It is a measured effect of time delay. It is not the formula to use for gravitational redshift.
Also the Shapiro effect would cancel out for distant sources. You would be just as likely to have massive bodies on either side along the path towards us. The effect is small anyway.
The formula is Delta T = SUM (-2GM(i)Ln(1-X.R)/c^3) where M(i) is the ith peturber and X and R are unit vectors from us to the source and us to the observer.
Plug in numbers and you see the effects are in microseconds versus travel times of years to Gigayears. Anyway you would need a huge amount more mass than is observed in conjunction with a huge assymetry of this mass to have a decent delay.
But this is a moot point. It does not give a redhsift/blueshift.
For that to be the case you have to use the gravitational redshift formula which is not a logarithmic dependence.
Redshift = SquareRoot(1-2GM/Rc^2).
As you can see that drops of as 1/R from an object. Even at the surface of the Sun this is a very small fractional change.
But even this is moot. Because light from a distant source would go through these very small changes both ways. It would be slightly blueshifted as it falls down the potential of the peturber and then the same shift to the red as it leaves the potential - thus canceling out.
Also due to the 1/R relationship you would need these ridiculous amounts of massive peturbers along the line of sight even if the shift was only red. This is ruled out from many other observations.
In summary - NEVER GET YOUR SCIENCE FROM JERROLD THACKER'S GOOFY WEBSITE.
I had some email correspondence with him a couple of years ago pointing out many physics errors on his site. He was rude from the get go. He is an old crank lost in his own world of psuedo physics and just wont listen to the obvious.

Replies to this message:
 Message 12 by RAZD, posted 03-23-2004 12:36 PM Eta_Carinae has replied

  
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 12 of 18 (94127)
03-23-2004 12:36 PM
Reply to: Message 11 by Eta_Carinae
03-23-2004 12:06 PM


Re: The Shapiro Effect
I figured someone with a nick like yours would be into astronomy ...
It would be slightly blueshifted as it falls down the potential of the peturber and then the same shift to the red as it leaves the potential - thus canceling out.
would also mean a blueshift on the approach to earth observatories (hubble included) which should tend to cancel out any initial red-shift.

we are limited in our ability to understand
by our ability to understand
Rebel American Zen Deist

This message is a reply to:
 Message 11 by Eta_Carinae, posted 03-23-2004 12:06 PM Eta_Carinae has replied

Replies to this message:
 Message 13 by Eta_Carinae, posted 03-23-2004 12:53 PM RAZD has replied

  
Eta_Carinae
Member (Idle past 4374 days)
Posts: 547
From: US
Joined: 11-15-2003


Message 13 of 18 (94131)
03-23-2004 12:53 PM
Reply to: Message 12 by RAZD
03-23-2004 12:36 PM


Re: The Shapiro Effect
would also mean a blueshift on the approach to earth observatories (hubble included) which should tend to cancel out any initial red-shift.
Why would it cancel out. The blueshift falling in the Earth's potential well is all but unobservable. Remember the Pound/Rebka experiment. It can only be done with a very sensitive experiment.
The formula is Redshift = SQRT[1-2GM/Rc^2].
Plug in the numbers - the shift is of the order of parts in 10^-14.
Whereas a redhsift from say a quasar is of the order 0.1 to 6.

This message is a reply to:
 Message 12 by RAZD, posted 03-23-2004 12:36 PM RAZD has replied

Replies to this message:
 Message 14 by RAZD, posted 03-23-2004 1:05 PM Eta_Carinae has replied

  
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 14 of 18 (94132)
03-23-2004 1:05 PM
Reply to: Message 13 by Eta_Carinae
03-23-2004 12:53 PM


Re: The Shapiro Effect
"tend to cancel"
not complete cancellation. I would be surprised to see a net blue-shift value from any observed object.
k?
the differences in values from objects of different masses (small stars to your quasar) should also be a means of showing that the Shapiro "effect" does not correlate with data.

This message is a reply to:
 Message 13 by Eta_Carinae, posted 03-23-2004 12:53 PM Eta_Carinae has replied

Replies to this message:
 Message 15 by Eta_Carinae, posted 03-23-2004 1:13 PM RAZD has replied

  
Eta_Carinae
Member (Idle past 4374 days)
Posts: 547
From: US
Joined: 11-15-2003


Message 15 of 18 (94135)
03-23-2004 1:13 PM
Reply to: Message 14 by RAZD
03-23-2004 1:05 PM


Re: The Shapiro Effect
The Shapiro effect is real. It is measured in the solar system from the delay of transmissions to space vehicles.
My argument is that
a) this effect has nothing to do with red/blue shifting - which has a different functional dependence
b) The delay from a distant source would only arithmetically increase if you had many close encounters with massive objects along the way and these objects would also really need to be assymetrically distributed to some extent.
Also the value of these delays is tiny compared to the travel times and also provide no information. You cannot tell the mass of an individual peturber - or even if any delay occurred since all wavelengths are affected the same it is an observational degeneracy.

This message is a reply to:
 Message 14 by RAZD, posted 03-23-2004 1:05 PM RAZD has replied

Replies to this message:
 Message 16 by RAZD, posted 03-23-2004 1:26 PM Eta_Carinae has replied

  
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