The Speed of Light is Not Constant

[Aqueous Id]

The meaning here is that the light distance and the unit of time being measured, must be at the same location as the light itself.

If you mean that to say there can be no warp, then I agree. Light can't observe itself warping. It can interfere with itself, but that's another thing, unless we could construct a scenario in which one leg of a split beam were warped and then brought back to interfere with the source. But I can't think of any way that can occur without returning those photons to the observation frame, which kills any of the effects Farsight claims occur. That is, all photons where the interference would be measured are back home in the observation frame. So that basically kills all warp, which kills the entire premise here. I'm still not sure what you're getting at. One of the problems with that last part of what you said is that photons can't stand still. They can only move at c.

 

[Aqueous Id]

Hard to believe everybody isn't pro science. The other path is like cutting off your nose because you don't like your face. The only drawback is the science being presented is the same thing over and over when cranks are ruling the roost.

Hey bruce. Yeah it does get monotonous. I would say that they are experiencing the delusions of Russell Crowe's character in A Beautiful Mind, only without the "beautiful". Homely maybe, sometimes dog-ugly. But definitely twisted. Am I right? Are they simply not capable of understanding what a reference frame is? I keep thinking I've diagnosed the syndrome. At least that's my guess today.

 

[paddoboy]

I see that a lot of good science is being presented by the pro-science folks, so the nuts are serving as a stimulus in the manner of devil's advocates.

I see many reasons why we do seem to be overflowing with cranks, one being that forums such as this are the only outlet they have.
Other reasons are "tall poppy syndrome"and of course delusions of grandeur.
Which is why I started the "Alternative theorists"thread and what I consider to be points that should be followed if any alternative theory has any validity.

I also realize that my simplisitc style may not adhere to the more precise mathematical scenario that a professional may use.



http://vimeo.com/89588121

 

[paddoboy]

BTW Aqueous, the last link of course was the beach I was referring to. Literally at my front door.
check it out from the 3.30 sec mark.

 

[nimbus]

This is part of why a massless photon can carry energy without gaining mass. And, no, the photon does not have a gravitational field. Grumpy

Grumps, I may be taking you out of context, but are you saying you don't associate a photon's energy as having a gravitational effect?
What happens when you stick a photon's energy in one side (stress-energy tensor)of the field equations, are you saying you expect no change on the other side (Einstein tensor) of that equation?

 

[nimbus]

Am I right? Are they simply not capable of understanding what a reference frame is? I keep thinking I've diagnosed the syndrome. At least that's my guess today.

I think with some it's a real belief that if you smash an analogy or simplified descriptive picture given as example of something scientific, then they think the mathematical model takes a dive too.
Didn't Godel use the Einstein's equations to show a rotating universe where time travel is possible both ways (future and past), funny that Farsight linked to a book 'advert' only about Godel and Einstein.

 

[Write4U]

Write4U

That is just wrong. The coordinate speed changes, the speed of light through spacetime does not. The time a photon takes to travel between the mirrors goes up the more acceleration bends spacetime, giving you a slower coordinate speed, but that is because the photon must travel a further distance as the curvature increases. All curved paths are longer than a straight path between the same two end points of the paths. The higher the acceleration/gravity, the more the curvature, the more the difference between coordinate speed and c. There is a difference of arrival time of the photon and the expected, derived and fixed coordinate speed. And that difference is time dilation.

Grumpy

Perhaps we are talking about different experiments, but Einstein (in a lecture about gravity) drew a picture of a box , accelerating upward (in a vacuum) at near SOL.
The box has a small hole in one side and has an observer inside the box.
At a certain point the box passes a light source and the light image enters throught the small hole and is recorded on the opposite wall.
Instead of a perfectly straight line, to the observer in the box it will look like the light is bending downward as if by gravity and will in fact strike the opposite wall at a lower point than if the box were stationary, because the box has moved upward in the mean time.

But even as the curved path is longer than a straight path between hole and opposite wall, the light will arrive at the very same time as if the box were stationary and the light beam would be perfectly straight.
Let me repeat, the photon always reaches the other side of the box at the same time, regardless if the box is in motion or stationary. This is due to the fact that "only" the box is moving and light always travels in a straight line, thus always reaches the other side at the same time as long as the distance between the walls remains the same.

What we experience with massless particles may be quite different to what is physically happening in reality.

 

[wellwisher]

Photons of energy move at the speed of light. These are both particles and waves, at the same time. The easiest way to explain a range of observations, paradoxes and anomalies is to assume, that although both particle and wave are connected, the particle follows a continuous function, while the wave follows a quantum/discontinuous function.

For example, if the wavelength was 1 meter and the photon only moves 1 cm, there is not time for a full wavelength to develop. However, one can show that the particle will nevertheless move 1 cm, even if there is no full wave. The speed of light the same in all references implies continuous function. The wavelength is reference dependent and therefore is not constant/continuous.

With respect to the double slit experiment, the particle only needs one slit. If the continuous motion of the particle does not create a full wavelength, due to the quantum wave function, then the full wavelength that will go through the slip, will come from a previously generated full wave. Since the wave functions of atoms are quantized, these can only react to full wavelengths.

Relative to curved paths, say we assume a continuous particle in motion connected to a discontinuous/quantum wave. If the particle follows the curved path, the particle can go further than one wavelength, going a to b, compared to a straight path. But in both cases, say only one wavelength had time to develop. The light appears to slow if we only look at the wave, since the fractional wave is not a full wave.

 

[Grumpy]

Write4U

But even as the curved path is longer than a straight path between hole and opposite wall, the light will arrive at the very same time as if the box were stationary and the light beam would be perfectly straight.
Let me repeat, the photon always reaches the other side of the box at the same time, regardless if the box is in motion or stationary.

That is simply wrong, the curved path means it takes the photon more time to cover that same coordinate distance. The coordinate distance is that between the hole and the wall in a straight line, the curved spacetime is longer(because it is curved)but the photon must cover the additional distance at exactly the same speed, it takes more time to travel a longer distance at the same speed and this is illustrative of time's dilation in an accelerating frame. The observer moving with the clock sees the photon at the same speed because his time is dilated too. But any outside observer will see the photon, traveling all the while at c, follow a bent path in a longer time than the coordinate distance would lead you to expect. That is time dilation and spacetime curvature. Photons never exceed lightspeed and bent paths are longer and mass causes spacetime to bend thus light takes longer to go the coordinate distance in a gravity field. It's coordinate speed is slower, it's actual speed through spacetime remains c.

Part of your misunderstanding is the position of the observer. In frame no difference would be seen, from a stationary frame the comoving observer's time is seen to go slower(dilated), light follows a bent path and it takes longer to "tick". Frame of reference causes lots of confusion in Realativity, but it is critical to understanding. You need to designate all of your statements with the frame of reference of the observer you are talking about.

Grumpy

 

[Farsight]

"The light is going half as fast and the second is twice as big."

The light is going half as fast but the second is half as long (.5t). Time dilates meaning it progresses more slowly.

If you're time dilated compared to me, your second is bigger than mine. One of your seconds is worth two of mine.

"Things slowing down" also means clocks tick at a slower rate. The motions within the clock function (dilate) according to the influences of gravity.

Yes, even when it's an optical clock.

It depends upon what definition of time you ascribe to since no single definition of time has a consensus following. My preferred definition of time is "an interval of change as measured by a clock." You can have a different definition, but if so I believe we would only be discussing semantics rather than your enlightening topic.

I think your definition is reasonable.

As to my example above, the distance light would travel would be different in each case. Away from the black hole the distance traveled per time interval would measure to be 1 mile using the clock away from the black hole. Using the same clock (away from the black hole) the distance light would travel per unit of time when close to the black hole, would be measured as 1/2 mile. But we cannot use the same clock since speed is a ratio relative to the time frame light is traveling in. Using the clock near the black hole the light distance would be 1/2 mile. but the clock at that location would instead measure time passed as 1/2t.

I think you're missing something here, forrest.

Even though light would travel twice as fast away from the black hole

There. The light travels twice as fast. That's it. It's that simple.

the distance that light would travel per unit of time at that location would remain constant.

No! The light travels twice as fast. End of story.

Both the rate of time and distance traveled would equally reduce or increase at the same rate maintaining a constant ratio between them. This also applies to time dilation caused by relative motion to the center of gravity at any particular location.

It isn't like that forrest. Honest. Gravitational time dilation alters the second. It doesn't alter the metre. There's radial gravitational length contraction, but hold your metre-rod so it's horizontal. It's the same old metre.

 

[PhysBang]

No! The light travels twice as fast. End of story.

It might be clearer if you would demonstrate an example with some numbers so you could demonstrate exactly how the physics works. Could you please do this?

It doesn't alter the metre. There's radial gravitational length contraction, but hold your metre-rod so it's horizontal. It's the same old metre.

Could you show us exactly where every textbook goes wrong in saying the opposite of that?

 

[Grumpy]

Farsight

First you deny that lightspeed in a vacuum is always c, even though the Theory of Relativity is based upon that well established and often observed fact.

Then you say this...

No! The light travels twice as fast. End of story.

...which is simply idiocy, as Einstein says(and we have since verified)NOTHING travels faster than light, and light always has a true speed through spacetime that is exactly c. You are basically saying that one c is twice as fast as c, which is simply breathtakingly idiotic.

Grumpy

PS I know you put people who know more than you about any subject on ignore, but that doesn't mean we can't point and laugh anyway.

 

[Grumpy]

forrest noble

My preferred definition of time is "an interval of change as measured by a clock.

As long as you understand that the interval exists whether or not your clock is there to measure it, this definition is accurate. But Einstein said that any process, no matter how irregular, is a valid clock. And clocks only describe time, they allow us to measure time, but they are not time, they don't create time and time still passes in the absence of any clock to measure it by.

Write4U

Perhaps we are talking about different experiments, but Einstein (in a lecture about gravity) drew a picture of a box , accelerating upward (in a vacuum) at near SOL.
The box has a small hole in one side and has an observer inside the box.

That is true, the observer in the box sees light as traveling exactly at lightspeed, but he is within the frame, he is seeing the coordinate speed(time between mirrors), timing it with slow time that he does not experience as slow. The stationary, outside observer sees the longer path at lightspeed and the slowing of the time in the moving frame. Every bit of this pivots about the axis that both observers see light as always traveling the same speed, c. Time, length and mass all change in the direction and to the extent that c is always seen as constant in and between all frames. It is a fact, to the extent we have been able to test it, that every photon in vacuum IS traveling at c, throughout the visible Universe and between any two points in our Universe. Farsight is wrong about this as well, as he usually is.

Again, you must specify the frame of the observer, as all frames see themselves as the normal ones, and there are differences between what each frame sees in other frames.

This is an accurate depiction of the various frames associated with the stationary(upper left, the same for all comoving observers), The relative constant(inertial)motion(upper right), The accelerated comoving observer(lower left)and the accelerated outside stationary observer(lower right). The dotted line in the illustration on the lower left is the curved spacetime line in a gravity field(IE stationary acceleration)..

Grumpy

 

[lpetrich]

A big problem with Farsight's argument here is that coordinates are fundamentally arbitrary. This important fact is often obscured by selection of coordinates that are related to certain features of what one is addressing, like symmetries. For example, for flat space, one can use coordinates associated with its translation symmetries, and one gets rectangular coordinates. That is also true for flat space-time.

That makes the coordinate speed of light meaningless, and no amount of Einstein-thumping can change that. Yes, Einstein-thumping as in treating Einstein's writings like some sacred book, complete with insisting that it is a great wrong to deny Einstein.

 

[forrest noble]

Grumpy,

"As long as you understand that the interval exists whether or not your clock is there to measure it, this definition is accurate. But Einstein said that any process, no matter how irregular, is a valid clock. And clocks only describe time, they allow us to measure time, but they are not time, they don't create time and time still passes in the absence of any clock to measure it by."

Yes, a valid point. Let me change my preferred definition of time to: Time is an interval of change and nothing more; the primary instrument to measure its passing we call a clock

 

[forrest noble]

Farsight,

If you're time dilated compared to me, your second is bigger than mine. One of your seconds is worth two of mine.

Not wrong but this thinking is just perspective and semantics. To understand it better I believe the preferred perspective would be that the clock is just running more slowly when time is dilated; i.e. time would be progressing more slowly. In this case one second on a non-dilated clock would be the same time interval as 1/2 second of the dilated clock. 1/2 mile measured in 1/2 t close to the black hole, would be the same speed as the un-dilated clock measuring t amount of time and the observer measuring a distance of 1 mile that light would travel within that time interval away from the black hole. The ratio, the speed of light, remains the same even though light is traveling twice as fast away from the black holes influence, in the hypothetical case I presented above.

 

[Grumpy]

forrest noble

Time is an interval of change

Not to be pedantic, Time is an interval, change is how we define that interval. The interval exists even if no change occurs, it is built into the structure of the Universe, not created by events.

Grumpy

 

[paddoboy]

forrest noble



Not to be pedantic, Time is an interval, change is how we define that interval. The interval exists even if no change occurs, it is built into the structure of the Universe, not created by events.

Grumpy

Bingo, Totally agree. I see change more connected to entropy than time.
Time will always exist as long as space/time exists, and in any model of the Universe including Einsteins original Static Universe.

 

[Aqueous Id]

I think with some it's a real belief that if you smash an analogy or simplified descriptive picture given as example of something scientific, then they think the mathematical model takes a dive too.

Depending who is doing the believing and who is doing the smashing that statement might take on a few dimensions. Certainly when it's the cranks doing the believing and a superficial poster such as me doing the smashing, the central disconnect as far as models go is that they have no idea what a model even is, much less basic math. As far as they know all math is flawed abstraction until they want to pretend to use it to prop up their claims. After copious arguments that any math offered is invalidated on grounds of being abstraction, they then return to posting their own mathless abstractions and their math-violating abstractions.

Didn't Godel use the Einstein's equations to show a rotating universe where time travel is possible both ways (future and past),

Yes in fact he notes that a light ray arrives at the same time it departs. The rotating universe is said to be equivalent to eliminating 3-space but I don't understand the connection. I am inclined to associate any premise which removes 3-space with any conclusion that makes time "eternal" as a restatement of the singularity that occurs in the Lorentz transformation at v=c. Whether or not this has anything to do with the idea Godel developed, I have no idea. But it did cross my mind. Another even more frivolous thought was that I remembered the "time capsule" that took Jodie Foster to "heaven" in Contact. It was mounted on several layers of gimbals so that it could rotate on each of the axes of 3-space, which could possibly be Sagan's reference to Godel's idea here, although it also suggests the rotation matrix in the Lorentz transform as well. This probably doesn't lead anywhere, but I remember thinking Sagan was clever to think of that for a time traveling ship. (Just as the idea that Dr Who's it's bigger on the inside than on the outside TARDIS was a clever reference to something related to relativity.) But I ramble.

funny that Farsight linked to a book 'advert' only about Godel and Einstein.

I've had him on ignore for a long time, so I missed that. Anything I pick up about what he's currently spouting is through the folks who quote him. But I gather by your remark that there's irony that he didn't go to Godel's 1949 paper and try to quote mine it. Maybe he'll be inclined to do that now.

 

[forrest noble]

forrest noble
Not to be pedantic, Time is an interval, change is how we define that interval. The interval exists even if no change occurs, it is built into the structure of the Universe, not created by events.
Grumpy

Remember, this is my preferred definition. Many would disagree.

"The interval exists even if no change occurs, it is built into the structure of the Universe, not created by events."

I have a different understanding of reality. And as you realize there is no standard accepted definition of time. There have been entire books written about the concepts and hypotheses concerning time. From my own opinion and related hypothesis time is a man-made concept. It is not part of the universe. It is simply a definition, understanding, hypothesis, etc. of intelligent beings.

I believe time cannot exist without change, change in matter or energy; change can be expressed as relative motion of some kind. Without motion of any sort, angular momentum, etc. time would have no meaning. I am not being a name-dropper here but I agree with this quote:

“When forced to summarize the general theory of relativity in one sentence: Time and Space and Graviton have no separate existence from matter.”
―Albert Einstein