I'm afraid you're in denial.
The Speed of Light is Not Constant
- Thread starter Farsight
- Start date
what ever you need to tell yourself.
Right now researchers are looking for gravitational waves generated by binary systems of strong gravitational fields, like some combination of two white dwarfs, neutron stars or even black holes.., in close orbit with eachother. The idea is that this kind of dynamic system should create changes in the gravitational field associated with the rapid and constant change in the locations of the center of gravitation of the two objects... The change(s) in the combined gravitational field propagate outward at the speed of light. Following from the logic involved and all other observation and experience, a mass of gravitational significance is required for a gravitational field to exist.
What you are suggesting is that once an object has collapsed, creating a BH and an associated event horizon, the mass of the BH no longer has any dynamic relationship, with the gravitational field outside the event horizon.... But that would mean that the gravitational field outside of an event horizon is not associated with any gravitational mass, in the present. This is the same as saying that once a gravitational field has been established it no longer requires a causal relationship with any mass.., or that any gravitational field TODAY, may have a causal relationship with a gravitational mass in the PAST, that no longer exists TODAY!
All current experience says that there is a causal relationship between a gravitational field and mass.., and that as the distribution and/or density of that mass changes, so does the gravitational field.
Though I am not personally, entirely comfortable with some of the implications and some interpretations of the following, it does have some merit for the discussion at hand.
What you are suggesting is that spacetime has some memory that is persistent and does not require matter/mass to tell it how to curve. I believe you are also presenting a modern interpretation of just what spacetime is. Which is not a bad thing in itself, but it is important to remember that the issue, however one interprets it, is Theoretical.
Note; In my own words, the modern interpretation of "spacetime" is dynamical, in that it assumes that spacetime is a causal component of gravitation; Where my own belief follows the more historical interpretaion that "spacetime" is kinematical, in that it describes how objects interact, rather than the cause or why of that interaction. This distinction in definition and interpretation is beginning to be of some importance, as attempts to develope a functional theory of quantum gravity are pursued. "Spacetime" in the modern interpretation is a big picture concept, that does not fit well with any quantum model.., and to some extent represents at least a portion of the conflict between a successful theory of quantum gravity and GR.
There isn't, krash. You can tell this if you note the context, where Einstein talks about the SR postulate, which was the constant speed of light. All the more so when you go back to the original German version, which features the word Geschwindigkeit, which means speed. Einstein wasn't talking about a velocity changing in the vector sense. He wasn't saying "light curves because it changes direction". That's a tautological nonsense. He was saying light curves because the speed of light varies with position. It curves like a car veers when it encounters mud at the side of the road. Like the way you steer a tank. Slow down the tank track on the left, and the tank turns left. Have a read of Ned Wright’s Deflection and Delay of Light. Note this: "In a very real sense, the delay experienced by light passing a massive object is responsible for the deflection of the light”. Light doesn’t curve because it curves, and it doesn’t curve because spacetime is curved. Einstein never said that. It curves because the speed of light varies with position. That's what Einstein said. it curves like sonar waves curve. Like this:
Image credit Ned Wright, see http://www.astro.ucla.edu/~wright/deflection-delay.html
So much like the light from behind the Sun is reflected because this light passes through the atmosphere of the Sun
The Suns Corona
uhh, there's those nauseating words again( logic and interpretation).
i have gathered these words are typically used by inexperience individuals.
amusing.
Farsight, I believe you are once again wrong in your interpretation.., and if Baez believes as you he also is mistaken. In that particular reference I believe that Einstein did intend the word "velocity" not speed.
Though it seems I do remember some reference in latter discussion (and the following is in my own words) where Einstein commented that a universally constant "speed" of light was only required within the context of special relativity and that even IF the speed of light were variable, it would have no adverse affect within the context of general relativity.
Obviously he was unaware of how entrenched people would become in their own interpretations of what he thought, once he was no longer able to engaged in the discussions hisself.
Did you have something constructive to say?
I don't find what you have gathered or find amusing to be constructive comment.., without the addition of some comment of substance, too often missing in your posts!
You often just clutter up a discussion with vaguely and sometimes not so vague, cryptic remarks.
actually, i did contribute even before this spewing of post #706.
just go back a page or such.
cryptic ?
who's the one using the word interpretation,
the only cryptic here is the one who is having the will to interpret everything, even if words are clearly used.
if there wasn't such a will of being a want to be intellect, then maybe interpretation would not be needed.
again amusing.
again
these words are typically used by inexperience individuals.
interpretation is a result of not understanding words or meanings that were used.
so it's done to attempt understanding using other words or meanings to fit the individuals mind.
when done by the individual that does not understand to begin with,
it always leads to continuous misunderstanding ,
which is exactly the situation.
interpretation,
every time i see that word it's nauseating,
it's the same as " short cuts " in mathematics
What I'm saying is that the gravity of a BH is a fossil field and that gravity is nonlinear.
http://www.einstein-online.info/spotlights/gravity_of_gravity
http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/black_gravity.html
Yep, he's not the first to mangle what Einstein has said, we have another who mangles Einstein's quotes, as well as Sean Carroll's.........and guess what? Both of them claim to have rewritten 20th/21st century cosmology, and each has ToE's.
krash661,
I was addressing a single issue raised in paddoboy's post, not the content of the entire thread. My response to your post was with respect to that post not the tread as a whole or anything you may have said during your entire life.
Neither of your last two posts, responding to my posts, contribute anything of value to any discussion of physics. If that had been your intent, I would have expected that you would have at least included some statement about your particular INTERPRETATION of the theoretical issues being discussed.
I don't generally respond to posts like your last two posts. Consider this to have been a slip....
Just for you I will clarify, I used the word interpretation intentionally to emphasize two points. One was that there are different theoretical perspectives on the particular issue I was addressing... And second to clearly establish my understand, or since we are iris cussing theory even belief.
I also used intentionally used the word logic.
Now you obviously seem to have some difficulty understanding the context and may even disagree.., though there is nothing of substance in your replays that demonstrates that, by reference or evidence.
I got carried away... Mostly on the wave front of what often seems to be nothing more than ridicule and trolling in many of your posts.
I will try to avoid this in the future.
I was addressing a single issue raised in paddoboy's post, not the content of the entire thread. My response to your post was with respect to that post not the tread as a whole or anything you may have said during your entire life.
Neither of your last two posts, responding to my posts, contribute anything of value to any discussion of physics. If that had been your intent, I would have expected that you would have at least included some statement about your particular INTERPRETATION of the theoretical issues being discussed.
I don't generally respond to posts like your last two posts. Consider this to have been a slip....
Just for you I will clarify, I used the word interpretation intentionally to emphasize two points. One was that there are different theoretical perspectives on the particular issue I was addressing... And second to clearly establish my understand, or since we are iris cussing theory even belief.
I also used intentionally used the word logic.
Now you obviously seem to have some difficulty understanding the context and may even disagree.., though there is nothing of substance in your replays that demonstrates that, by reference or evidence.
I got carried away... Mostly on the wave front of what often seems to be nothing more than ridicule and trolling in many of your posts.
I will try to avoid this in the future.
I understood what you meant. I may have at some time in the past been in agreement. I am not as certain any longer. The fossil field concept does not seem to me to be sustainable. As I said, or attempted to say, while it can be conceptually consistent with a modern "interpretation" (in quotes for krash) of GR, there are some difficulties with that model from the context of quantum gravity...
danshawen
Valued Senior Member
See:
http://en.wikipedia.org/wiki/Shapiro_delay
Even with 1980's technology, Irwin Shapiro was able to measure the delay "slowing" of the speed of light as measured for a microwave signal bounced from here to the planet Venus. On the round trip, the speed of light slowed down, as in NOT CONSTANT. The speed of light is a constant only in an inertial reference frame. Not in an accelerated reference frame. Not in a reference frame that is affected by a gravitational field
So, what else were you arguing about?
http://en.wikipedia.org/wiki/Shapiro_delay
Even with 1980's technology, Irwin Shapiro was able to measure the delay "slowing" of the speed of light as measured for a microwave signal bounced from here to the planet Venus. On the round trip, the speed of light slowed down, as in NOT CONSTANT. The speed of light is a constant only in an inertial reference frame. Not in an accelerated reference frame. Not in a reference frame that is affected by a gravitational field
So, what else were you arguing about?
In order to help counter that usual deception that Farsight engages in, let's look at what the Baez article says about "speed" for "ceiling and floor observers".
So here we see that the article says that we can think of something like speed, "pseudo speed", that matches the coordinates that we can assign to events. The most well-defined nothin of speed in GR holds that the speed of light is always the same.Earlier in Baez Article said:
To be clear, Farsight argues that the actual speed of light changes with position, not merely the coordinate speed. The Baez article has science on its side, Farsight has his personal convictions and nothing else.
I'm afraid you're wrong. He was challenging his own SR postulate. That was the constant speed of light, not the constant vector-quantity velocity. You can change the vector-quantity velocity of light with something as simple as a mirror or a prism. Go and read the original material, and the OP, and go read the Baez-website article too. You might then appreciate that it was written by Don Koks not John Baez. Don't ignore all those things because you prefer to cling to popscience myth and ignorance.
There is no such reference. You're kidding yourself.OnlyMe said:
All: PhysBang said this on another forum:
"In a sense, this was done in 1905, when Einstein developed special relativity. This constancy of the speed of light is a postulate of the theory, so it is "shown" through the effectiveness and practicality of the theory. The same is true for general relativity, developed in 1915, which holds that the speed of light is constant at any infinitesimal region of a coordinate system".
Note that the speed of light is constant in an infinitesimal region. That means it isn't constant in the room you're in.
danshawen
Valued Senior Member
I saw this argument elsewhere. The answer to this is a bit tricky. Still don't know what happened to my colleagues, who might have some other ideas on the subject.
Measuring the speed of light precisely, particularly in a small space with any apparatus that is composed of matter will be impossible without the apparatus adding its own quantized bias to the measurement.
I think it is likely that the speed of light is constant whenever it propagates in a perfectly straight line, whatever that is. This may be impossible to determine in a smaller space. As we have suggested, space itself, like mass, is emergent from the more fundamental components of time and energy.
I was present for a colloquia lecture Bill Phillips gave at the UofMD about his quantum fountain clock. It was the first lecture I had ever seen given with a green laser pointer (not advisable around reflective surfaces or with an audience closer than about 75 feet, due to infrared lasing!). He also had a small, bad demonstration of one of the first Levitrons. I was inspired enough by that to give a lecture on Higgs with a much more advanced Levitron, and the audience loved it. I made a cartoon image of the Higgs for the top that was levitated almost motionless as the electronic base took care of the needed rotation (about 10-20 rpm).
Measuring the speed of light precisely, particularly in a small space with any apparatus that is composed of matter will be impossible without the apparatus adding its own quantized bias to the measurement.
I think it is likely that the speed of light is constant whenever it propagates in a perfectly straight line, whatever that is. This may be impossible to determine in a smaller space. As we have suggested, space itself, like mass, is emergent from the more fundamental components of time and energy.
I was present for a colloquia lecture Bill Phillips gave at the UofMD about his quantum fountain clock. It was the first lecture I had ever seen given with a green laser pointer (not advisable around reflective surfaces or with an audience closer than about 75 feet, due to infrared lasing!). He also had a small, bad demonstration of one of the first Levitrons. I was inspired enough by that to give a lecture on Higgs with a much more advanced Levitron, and the audience loved it. I made a cartoon image of the Higgs for the top that was levitated almost motionless as the electronic base took care of the needed rotation (about 10-20 rpm).
again...
if there wasn't such a will of being a want to be intellect, then maybe interpretation would not be needed.
also, the contribution would be seen.
simple.
FROM YOUR OWN LINK,
first,
" This article needs attention from an expert in Physics. Please add a reason or a talk parameter to this template to explain the issue with the article. WikiProject Physics (or its Portal) may be able to help recruit an expert. (November 2008) "
and second,
" The experiments have been repeated many times since then, with increasing accuracy.
" the speed of propagation of a light ray decreases as it passes through a region of decreasing gravitational potetial "
passing through a medium causes the path/direction to change.
propagation-
impel something forward: to move or transmit something such as a sound or light wave forward through a medium such as air
then further down on that link,
Calculating time delay
" the effect may be considered as a special case of gravitational time dilation "
" The measured elapsed time of a light signal in a gravitational field is longer than it would be without the field, and for moderate strength near-static fields the difference is directly proportional to the classical gravitational potential, precisely as given by standard gravitational time dilation formulas. "
" Time delay due to light traveling around(path change) a single mass
if light actually slowed it's speed, gravity probe B would have not confirmed relativity accurate.
simple.
This is a pathetic level of discourse for purported physics discussion. Einstein is dead. The end-all of Special Relativity was not Einstein's 1905 paper; that was the beginning with contributions by Minkowski, Poincaré, Weinberg and others contributed to how modern physics understands special relativity. Likewise, the development of General Relativity continued after Einstein's death -- so relying on Farsight's self-serving textual interpretations is sharing a quaint and backwards-looking priestly authority, but it is not physics.
Farsight has made hay on the point that because space-time is curved, the coordinate speed of light is not constant, but so what. Coordinates aren't physics. In General Relativity, coordinates are bubkes because any smooth coordinates may be used to describe local physics equally well; the geometry and physics of space-time are contained in the space-time metric (and its necessary variation) which has a representation in any smooth coordinate system. So while the local coordinate speed of light may vary from position to position and may even be anisotropic, since the metric is the connection between coordinates and physics, it does not follow that the local physical speed of light is not constant or anisotropic. And all physics is local.
So confusing a non-local coordinate speed of light with a local physical speed of light in curved space-time is a form of anti-scientific equivocation -- the confusion of two definition of a word of phrase.
This isn't easy stuff -- Einstein himself struggled with these concepts for 2 years. But eventually he adopted the principle of general covariance and built it into general relativity.
This is an equivocation because "speed of light" is a term of art in special and general relativity for the propagation speed of massless phenomena in vacuum.
I really don't understand in what context OnlyMe could have found such a statement by Einstein. But, I don't understand Farsight's objection to the purported paraphrase unless Farsight accepts that Einstein's General Relativity requires a constant and isotropic local physical speed of light.
Note that this is clearly a statement of the coordinate speed of light and not a discussion of the physical speed of light varying.