Light

[MadIce]

Re: Light

<div class='quotetop'>QUOTE(\"\"Gary Oas\"\")</div>

The concept of velocity dependent mass, relativistic mass, is examined and is found to be inconsistent with the geometrical formulation of special relativity. This is not a novel result; however, many continue to use this concept and some have even attempted to establish it as the basis for special relativity. It is argued that the oft-held view that formulations of relativity with and without relativistic mass are equivalent is incorrect. Left as a heuristic device a preliminary study of first time learners suggest that misconceptions can develop when the concept is introduced without basis. In order to gauge the extent and nature of the use of relativistic mass a survey of the literature on relativity has been undertaken. The varied and at times self-contradicting use of this concept points to the lack of clear consensus on the formulation of relativity. As geometry lies at the heart of all modern representations of relativity, it is urged, once again, that the use of the concept at all levels be abandoned.[/b]

On the Abuse and Use of Relativistic Mass by Gary Oas.

<div class='quotetop'>QUOTE(\"\"Gary Oas\"\")</div>

A lengthy bibliography of books referring to special and/or general relativity is provided to give a background for discussions on the historical use of the concept of relativistic mass.[/b]

On the Use of Relativistic Mass in Various Published Works by Gary Oas

Harte,

Have a look at these papers. Maybe it helps to get relativistic mass in perspective.

 

[Harte]

Re: Light

<div class='quotetop'>QUOTE(\"thenumbersix\")</div>

?
Quote:
Originally Posted by Harte
Here you should say \"the speed that all electromagnetic energies protrude...\" All energies do not propagate at lightspeed.

Which ones do you think do not ? With gravity the book is still out on this one. This goes back to a speed of gravity thread. Is this an inherent limit in space. Does gravity propogate at the speed of space ? (or the speed the 'ripples', if you like, in space spread out - very bad analogy)
[/b]

Six,
I know I was nit-picking here, but most energies do not propagate at lightspeed. How long does it take for a spoon handle to propagate heat energy to your hand from the bowl? Waves on water are energy propagation. Sound waves similarly.

<div class='quotetop'>QUOTE(\"thenumbersix\")</div>

?Though has light been measured within the gravity well of the sun, we may see some acceleration as it escapes it, this would still only be relative to an observer outside and in a different portion of space under different 'stresses'. As far as the light is concerned it is travelling at the speed of light... ?
[/b]

Light cannot be measured at any speed other than the speed of light in whatever medium it's traveling through. This is a fact and is not dependant on who is doing the measuring or what his velocity relative to the light beam he is measuring may be. In your example of the space around the sun, if you want to say that the light first travels through a layer (or layers) of gaseous emissions from the sun and then into a (pretty much) vacuum, then you would see a change in speed. Thus is because light travels faster in a vacuum. But gravity will not change the speed of any light it may affect. It doesn't matter who measures the speed of the light in question. If you were a photon leaving the sun, you'd measure yourself at the same speed as Joe Blow with the telescope that is looking at you from Earth. This is what Einstein meant by C being a universal constant.

Think of yourself riding in a passenger car on a train that is moving at 10 mph. You stand in the aisle and throw a ball (at, say, 5 mph) forward in the direction of travel of the train. Everyone on the train shares your reference frame. They all see the ball going 5 mph forward. Some guy that is stationary and outside the train, looking in the window, would see the ball moving forward at 15 mph (train speed + ball speed.) He is not in your reference frame so he sees things differently. Now substitue photon for ball and C for the 5 mph ball speed. You would think that the stationary observer would see the photon moving at 10mph+C. But he would not, he would see, just like you and your fellow travelers would see, the photon moving in the direction of the train's forward motion at a speed equal to C. The speed of light is constant, regardless of your reference frame. It is this postulate that leads to time dilation, constriction of length and all the other wierd things special relativity predicted that have since been shown to be true.

Harte

<div class='quotetop'>QUOTE(\"MadIce\")</div>

Harte,

Have a look at these papers. Maybe it helps to get relativistic mass in perspective.[/b]

Madice,
Gary Oas' postings on the matter of relativistic mass came up when I tried to find more on the subject. It was his info among others that caused my confusion. The use of spacetime geometry to explain how light is bent is all well and good. It can also explain how light is trapped in a black hole. My problem is with the need for two masses in gravitational attraction. Of course, this idea of both masses being necessary is Newtonian. Don't tell me I'll have to learn tensor mathematics to understand this.

Harte

 

[thenumbersix]

Re: Light

<div class='quotetop'>QUOTE(\"Harte\")</div>

Six,
I know I was nit-picking here, but most energies do not propagate at lightspeed. How long does it take for a spoon handle to propagate heat energy to your hand from the bowl? Waves on water are energy propagation. Sound waves similarly.
[/b]

Was thinking just electromagnetic waves really..



<div class='quotetop'>QUOTE(\"Harte\")</div>

Light cannot be measured at any speed other than the speed of light in whatever medium it's traveling through. This is a fact and is not dependant on who is doing the measuring or what his velocity relative to the light beam he is measuring may be. In your example of the space around the sun, if you want to say that the light first travels through a layer (or layers) of gaseous emissions from the sun and then into a (pretty much) vacuum, then you would see a change in speed. Thus is because light travels faster in a vacuum. But gravity will not change the speed of any light it may affect. It doesn't matter who measures the speed of the light in question. If you were a photon leaving the sun, you'd measure yourself at the same speed as Joe Blow with the telescope that is looking at you from Earth. This is what Einstein meant by C being a universal constant.

Think of yourself riding in a passenger car on a train that is moving at 10 mph. You stand in the aisle and throw a ball (at, say, 5 mph) forward in the direction of travel of the train. Everyone on the train shares your reference frame. They all see the ball going 5 mph forward. Some guy that is stationary and outside the train, looking in the window, would see the ball moving forward at 15 mph (train speed + ball speed.) He is not in your reference frame so he sees things differently. Now substitue photon for ball and C for the 5 mph ball speed. You would think that the stationary observer would see the photon moving at 10mph+C. But he would not, he would see, just like you and your fellow travelers would see, the photon moving in the direction of the train's forward motion at a speed equal to C. The speed of light is constant, regardless of your reference frame. It is this postulate that leads to time dilation, constriction of length and all the other wierd things special relativity predicted that have since been shown to be true.

Harte
[/b]

Quite right !