Theoretical Posted January 4, 2015 Share Posted January 4, 2015 Is what this guy is saying true? I've searched the internet for an answer. So far haven't found anything on this. Thanks! http://www.speed-light.info/speed_of_light_variable.htm Link to comment Share on other sites More sharing options...
xyzt Posted January 4, 2015 Share Posted January 4, 2015 (edited) Is what this guy is saying true? I've searched the internet for an answer. So far haven't found anything on this. Thanks! http://www.speed-light.info/speed_of_light_variable.htm The author, Raef Fanous, is a well known crank who has some other weird claims about the Khoran predating Einstein's relativity. Edited January 4, 2015 by xyzt Link to comment Share on other sites More sharing options...
Mordred Posted January 4, 2015 Share Posted January 4, 2015 (edited) The speed of light is invarient in all inertia frames. The author of this page is on crack Lol I see xyzt confirms my opinion of the author Edited January 4, 2015 by Mordred Link to comment Share on other sites More sharing options...
Theoretical Posted January 4, 2015 Author Share Posted January 4, 2015 The author, Raef Fanous, is a well known crank who has some other weird claims about the Khoran predating Einstein's relativity.Ok. Not surprised. I was like, what the frick is this all about lol. I guess the admins can move this to speculation. So to get this straight, gravity does not change the speed of light in any way shape or form, right? Link to comment Share on other sites More sharing options...
Mordred Posted January 4, 2015 Share Posted January 4, 2015 Correct it is invariant in a vacuum. Link to comment Share on other sites More sharing options...
Robittybob1 Posted January 4, 2015 Share Posted January 4, 2015 Ok. Not surprised. I was like, what the frick is this all about lol. I guess the admins can move this to speculation. So to get this straight, gravity does not change the speed of light in any way shape or form, right? But it does change the rate of time and what about length? So if time and length vary how can you be sure about velocity? Link to comment Share on other sites More sharing options...
Mordred Posted January 4, 2015 Share Posted January 4, 2015 There is no need to move to speculation as it's a direct question on a main stream theory Link to comment Share on other sites More sharing options...
xyzt Posted January 4, 2015 Share Posted January 4, 2015 Ok. Not surprised. I was like, what the frick is this all about lol. I guess the admins can move this to speculation. So to get this straight, gravity does not change the speed of light in any way shape or form, right? The local speed of light in vacuum is invariant. The coordinate speed of light is variant. The crank is talking about the coordinate speed of light, an entity that is devoid of any physical meaning. This thread belongs in the Trash. Link to comment Share on other sites More sharing options...
Theoretical Posted January 4, 2015 Author Share Posted January 4, 2015 Correct it is invariant in a vacuum.What about space itself? I was reading astronomers are aware of objects that appear to be moving faster than c. I understand the object itself isn't moving faster than c, but what about the fabric of space? Link to comment Share on other sites More sharing options...
Robittybob1 Posted January 4, 2015 Share Posted January 4, 2015 The local speed of light in vacuum is invariant. The coordinate speed of light is variant. The crank is talking about the coordinate speed of light, an entity that is devoid of any physical meaning. This thread belongs in the Trash. It's got a name, so explain coordinate speed of light please? Link to comment Share on other sites More sharing options...
xyzt Posted January 4, 2015 Share Posted January 4, 2015 (edited) It's got a name, so explain coordinate speed of light please Light follows null geodesics: [math]0=(1-r_s/r)(cdt)^2-\frac{dr^2}{1-r_s/r}[/math] where: c=local speed of light r=Schwarzschild radial coordinate [math]r_s[/math] = Schwarzschild radius t=Schwarzschild time coordinate From the above , it follows immediately that : [math]\frac{dr}{dt}=c(1-r_s/r)[/math] The expression [math]\frac{dr}{dt}[/math] is known as the coordinate speed of light. Edited January 4, 2015 by xyzt Link to comment Share on other sites More sharing options...
Mordred Posted January 4, 2015 Share Posted January 4, 2015 Space is simply volume. The spacetime fabric is oft misunderstood. GR does not teach us that space is composed of a fabric. The expansion of space being faster than c depends on the distance being measured. Per Mpc space expands the same at all locations not gravitationally bound. That rate is the Hubble constant roughly 70/km/sec/Mpc. Hubbles law states the greater the distance the greater the recessive velocity. [latex]v_{recessive}=H_oD [/latex] So lets say we have two objects 10 Mpc apart. The next second expansion affects each Mpc by 70 km. So we gained 700. Km. Now if your original seperation distance is however equal to the Hubbles sphere. (c*age of universe.) Each Mpc between us and the Hubbles sphere would add up the same way 70 km/Mpc. The result is an Apparent recessive velocity greater than c. However the object measured has no inertia neither does space. It is simply an increase in volume whose total change between two objects depends on the seperation distance. http://cosmology101.wikidot.com/redshift-and-expansion You can find numerous articles to help understand expansion in the misconceptions section of my site http://cosmology101.wikidot.com/ What about space itself? I was reading astronomers are aware of objects that appear to be moving faster than c. I understand the object itself isn't moving faster than c, but what about the fabric of space? Link to comment Share on other sites More sharing options...
Theoretical Posted January 4, 2015 Author Share Posted January 4, 2015 Then the ression velocity can exceed c? This Wikipedia article is interesting: http://en.m.wikipedia.org/wiki/Faster-than-light#Space-time_distortion "...general relativity does allow *the space between distant objects to expand* in such a way that they have a "recession velocity" which exceeds the speed of light, and it is thought that galaxies which are at a distance of more than about 14 billion light-years from us today have a recession velocity which is faster than light." What exactly does it mean by space expanding? Is this analogous to stretching a balloon? Link to comment Share on other sites More sharing options...
Mordred Posted January 4, 2015 Share Posted January 4, 2015 The balloon analogy is used to describe expansion. These two articles are good reading on expansion and the misconceptions superluminal expansion http://www.phinds.com/balloonanalogy/: A thorough write up on the balloon analogy used to describe expansion http://tangentspace.info/docs/horizon.pdf:Inflation and the Cosmological Horizon by Brian Powell The last is excellent and easily understood it was designed to answer forum questions by a professor friend of mine Questions on expansion has been answered numerous times in the astronomy forum which also covers cosmology. You can also look there Link to comment Share on other sites More sharing options...
MigL Posted January 4, 2015 Share Posted January 4, 2015 Gravity does not affect the speed of light. As Mordred has stated it is invariant in a vacuum. Gravity does affect time, so you're wondering why change in distance per change in time, or speed, shouldn't be affected. Well the effect is a little more subtle. Light being a wave ( picture a simple sine ), slowing time effectively increases the period of the wave ( stretches the peaks and troughs apart ). In other words, for light climbing out of a gravitational well, the wavelength increases and shifts towards the red, but its speed is always c . Link to comment Share on other sites More sharing options...
Theoretical Posted January 4, 2015 Author Share Posted January 4, 2015 The local speed of light in vacuum is invariant. The coordinate speed of light is variant. The crank is talking about the coordinate speed of light, an entity that is devoid of any physical meaning. This thread belongs in the Trash. I agree the author of that page seems ridiculous with all the religious nonsense. But I read on Wikipedia that the coordinate system means they're measuring from their (relative to an implied observer) point of view. So it's true that we could see, from our perspective, other objects traveling faster than 3E+8 m/s? And is it true that a free falling rocket toward a sun that suddenly turns on the rocket such that it's no longer falling toward the sun will go from measuring the local speed of light from 299792458 m/s to over 299792458 m/s? Reference: http://en.m.wikipedia.org/wiki/Coordinate_time Link to comment Share on other sites More sharing options...
xyzt Posted January 4, 2015 Share Posted January 4, 2015 (edited) So it's true that we could see, from our perspective, other objects traveling faster than 3E+8 m/s? No, it is not true, the formula I derived for you show that: [math]\frac{dr}{dt}=c(1-r_s/r)[/math] so, [math]\frac{dr}{dt}<c[/math]. Always. And is it true that a free falling rocket toward a sun that suddenly turns on the rocket such that it's no longer falling toward the sun will go from measuring the local speed of light from 299792458 m/s to over 299792458 m/s? No, it is not true. Edited January 4, 2015 by xyzt Link to comment Share on other sites More sharing options...
Theoretical Posted January 4, 2015 Author Share Posted January 4, 2015 Ok. One confusing thing. All of the articles on GR provide equations saying it must be in an inertial frame. Inertia itself doesn't change c or time dilation, right? Because velocity changes time dilation. So I thought about the experiment of synchronized clocks, where one clock went on a trip, but when it returned the clock that went on the plane was slow. It's interesting because one could say that the planet was moving relative to the clock on the plane, but yet the clock on earth didn't slow down. So the only difference I see is that the clock on the plane experienced momentary inertial forces as it accelerated, while the clock on earth did not. Is that what the inertial frames is all about in GR because I don't see inertia (an accelerating object cause by the movement in 3D space) in the equations? I mean, if we made an object spin around a small radius at a high rate causing high g-forces at low velocities, that doesn't cause time dilation, right? Thanks!! Clarification: I know a spinning object experiences time dilation because of its speed. My question was regarding the inertial forces itself. If we made the spin radius even smaller, then the g-forces increase at the same velocity. But I don't think that changes the time dilation. Link to comment Share on other sites More sharing options...
xyzt Posted January 4, 2015 Share Posted January 4, 2015 Ok. One confusing thing. All of the articles on GR provide equations saying it must be in an inertial frame. Inertia itself doesn't change c or time dilation, right? Because velocity changes time dilation. So I thought about the experiment of synchronized clocks, where one clock went on a trip, but when it returned the clock that went on the plane was slow. It's interesting because one could say that the planet was moving relative to the clock on the plane, but yet the clock on earth didn't slow down. So the only difference I see is that the clock on the plane experienced momentary inertial forces as it accelerated, while the clock on earth did not. Is that what the inertial frames is all about in GR because I don't see inertia (an accelerating object cause by the movement in 3D space) in the equations? I mean, if we made an object spin around a small radius at a high rate causing high g-forces at low velocities, that doesn't cause time dilation, right? Thanks!! Clarification: I know a spinning object experiences time dilation because of its speed. My question was regarding the inertial forces itself. If we made the spin radius even smaller, then the g-forces increase at the same velocity. But I don't think that changes the time dilation. I cannot parse the above word salad but I can tell you one thing: you seem to mix in the "Twins Paradox". The short answer is that twins are not symmetric, the one that "turned around" had to experience a longer path through spacetime. In relativity, longer path through spacetime means (paradoxically) shorter elapsed proper time. If you want to learn relativity, I suggest that you: -take a class -read a book ("Basic Relativity" by Robert A. Mould is an excellent, modern treatment and you can get it for only 18$ on Amazon). Posting word salads and asking people to unwind them is not the proper way of learning. 2 Link to comment Share on other sites More sharing options...
studiot Posted January 4, 2015 Share Posted January 4, 2015 xyzt Posting word salads and asking people to unwind them is not the proper way of learning. +1 Link to comment Share on other sites More sharing options...
Theoretical Posted January 4, 2015 Author Share Posted January 4, 2015 you seem to mix in the "Twins Paradox".That's it. It led me to the Wikipedia article on the Twin paradox, which clarified my question. Thanks a lot.http://en.m.wikipedia.org/wiki/Twin_paradox +1 I'll have to learn about this +1. I'd give a lot of people +1's if I knew how. Or maybe it's posting a +1 lol. I always access this forum with a mobile phone. 1 Link to comment Share on other sites More sharing options...
StringJunky Posted January 4, 2015 Share Posted January 4, 2015 That's it. It led me to the Wikipedia article on the Twin paradox, which clarified my question. Thanks a lot. http://en.m.wikipedia.org/wiki/Twin_paradox I'll have to learn about this +1. I'd give a lot of people +1's if I knew how. Or maybe it's posting a +1 lol. I always access this forum with a mobile phone. You can't rep someone in the phone version of the site unless you go into the full PC version ....which is not practical because you would have to zoom the page too large to see the rep buttons on each post. Link to comment Share on other sites More sharing options...
Mordred Posted January 4, 2015 Share Posted January 4, 2015 I work from the phone as well I usually switch to full version when I add rep points Then switch back Link to comment Share on other sites More sharing options...
Robittybob1 Posted January 4, 2015 Share Posted January 4, 2015 Is what this guy is saying true? I've searched the internet for an answer. So far haven't found anything on this. Thanks! http://www.speed-light.info/speed_of_light_variable.htm Light (photons) fall as fast as lead balls in a gravitational field. I had always thought of light falling much slower than other objects in the same gravitational field. Because light falls in a G field the light path (in a light clock) is longer and hence time slows down, because it goes further in a longer time therefore velocity stays the same.Velocity = c. The speed doesn't go up but the frequency does (to an outside observer) In the view of the free falling observer I have a feeling the frequency would stay the same. The question is would then the outside observer see the same light in the same phase or different phases of the sine wave? Link to comment Share on other sites More sharing options...
Strange Posted January 6, 2015 Share Posted January 6, 2015 Light (photons) fall as fast as lead balls in a gravitational field. I don't think that is correct. That is true for Newtonian gravity, but that gives half the deflection that GR does. Link to comment Share on other sites More sharing options...
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