[questionposter]

Spyman, on 22 March 2012 - 12:42 PM, said:

I stand corrected, the distant observer can't see the curving of space and therefore the distance covered by light seems shorter for him.

However, light should still always be measured at "c" because of the Lorentz Transformation

"Since relativity postulates that the speed of light is the same for all observers, the Lorentz transformation must preserve the spacetime interval between any two events in Minkowski space."

The transformation also sort of demonstrates how you can't even achieve the speed of light, seeing as how events asymtote at the frame-rate of "c" thus making it unachievable.

This post has been edited by questionposter: 22 March 2012 - 11:37 PM

[granpa]

it is always measured 'locally' at c

[Spyman]

questionposter, on 22 March 2012 - 11:34 PM, said:

However, light should still always be measured at "c" because of the Lorentz Transformation

"Since relativity postulates that the speed of light is the same for all observers, the Lorentz transformation must preserve the spacetime interval between any two events in Minkowski space."

The transformation also sort of demonstrates how you can't even achieve the speed of light, seeing as how events asymtote at the frame-rate of "c" thus making it unachievable.

I don't think you can explain the phenomena in the example provided by The time Traveller in post #31 with Lorentz transformations.

The speed of light is c for both observers, but the distant observer is unable to measure the real length along light's curved path inside a gravity field.

This post has been edited by Spyman: 23 March 2012 - 08:55 AM

[questionposter]

Spyman, on 23 March 2012 - 08:55 AM, said:

I don't think you can explain the phenomena in the example provided by The time Traveller in post #31 with Lorentz transformations.

The speed of light is c for both observers, but the distant observer is unable to measure the real length along light's curved path inside a gravity field.

So what's the point of saying that if light is still "c" for all observers?

[Spyman]

questionposter, on 23 March 2012 - 12:09 PM, said:

So what's the point of saying that if light is still "c" for all observers?

To point out that the speed of photons through space are still c for all observers, even if it appears to be slower for some.

[Aguirre]

Spyman, on 23 March 2012 - 12:33 PM, said:

To point out that the speed of photons through space are still c for all observers, even if it appears to be slower for some.

Don`t forget the eigentime (Eigenzeit) for every Photon that has a eigentime Zero.

[Spyman]

Aguirre, on 23 March 2012 - 03:50 PM, said:

Don`t forget the eigentime (Eigenzeit) for every Photon that has a eigentime Zero.

Sorry, unable to understand that.

[Aguirre]

Spyman, on 23 March 2012 - 12:33 PM, said:

To point out that the speed of photons through space are still c for all observers, even if it appears to be slower for some.

To explain the constance of the speed of light you have at least find a reason where this constance
comes from. Otherwise it comes falling down from heaven.
And i think the constant of the speed of light is connected to the Eigenzeit.
No more to say at the moment.

[questionposter]

Aguirre, on 23 March 2012 - 07:48 PM, said:

To explain the constance of the speed of light you have at least find a reason where this constance
comes from. Otherwise it comes falling down from heaven.
And i think the constant of the speed of light is connected to the Eigenzeit.
No more to say at the moment.

No it has to do with how the "distance" between you and the photon decreases, like dilation, only it's more to do with the frame-rate of events.

[Spyman]

Aguirre, on 23 March 2012 - 07:48 PM, said:

To explain the constance of the speed of light you have at least find a reason where this constance
comes from. Otherwise it comes falling down from heaven.
And i think the constant of the speed of light is connected to the Eigenzeit.
No more to say at the moment.

I am not trying to explain the constancy of lightspeed, it is an confirmed fact by experimental observation and don't need a reason.

Eigenzeit seems to translate from german to "proper time" which is a concept in the theory of relativity and connected to lightspeed.

I still don't understand what you are trying to say and how it is related to what I said and the context of current conversation.

[juanrga]

morgsboi, on 11 November 2011 - 11:58 PM, said:

Only matter is affected by gravity. And if light is made up of matter, why won't it destroy anything it goes through?

Would this answer be correct:

Black holes warp space-time so much that any particle that crosses the event horizon finds that simply moving forward in time also moves it toward the singularity at the center of the black hole. The only way anything could escape the black hole would be if it could travel faster than light. You can view an event horizon as being defined to be the boundary between an escape velocity that is lower than c and an escape velocity that has to be greater than c.


Another question that I can't answer is: Would light bounce between the event horizon and the mass? Because Professor Stephen Hawking says that not even a black hole is truly black.
So even in the slightest, light should reflect off the black hole but only to get sucked in again as it can't escape the event horizon.

It is not right that only matter is affected by gravity. Light is also affected. For instance light bends around Sun due to gravity.

Neither "light is made up of matter".

[morgsboi]

juanrga, on 14 April 2012 - 05:22 PM, said:

It is not right that only matter is affected by gravity. Light is also affected. For instance light bends around Sun due to gravity.

Neither "light is made up of matter".

This topic was a while ago. I did a lot of reading up on it. And no, light isn't affected as it is the light which follows the space-time (which has been warped by gravity).

[pmb]

juanrga, on 14 April 2012 - 05:22 PM, said:

It is not right that only matter is affected by gravity. Light is also affected. For instance light bends around Sun due to gravity.

Neither "light is made up of matter".

Physicists understand light to be a form of matter. This viewpoint started with Eintein when he wrote his papers on relativity. For example; in Einstein's 1916 paper which is a review on gravity. In section 14 Einstein writes

Quote

We make a distinction hereafter between "gravitational field" and "matter" in this way, that we denote everything but the gravitational field as "matter". Our use of the word includes not only matter in the ordinary sense but the electromagnetic field itself.

I had a rather new undergraduate physics text around here somewhere which defined the term in that way. I can't find it right now. But I know of no valid reason to use the term otherwise. In fact it makes sense to think of the electric field and magnetic field in this way too.

juanrga, on 14 April 2012 - 05:22 PM, said:

Neither "light is made up of matter".

On what basis do you make this assertion?

[juanrga]

morgsboi, on 15 April 2012 - 09:39 PM, said:

This topic was a while ago. I did a lot of reading up on it. And no, light isn't affected as it is the light which follows the space-time (which has been warped by gravity).

And in general relativity, matter also follows the spacetime (which has been warped by gravity). One cannot say that matter is affected by gravity whereas light is not, when both are effected and 'bend'.

[pmb]

juanrga, on 16 April 2012 - 02:59 PM, said:

And in general relativity, matter also follows the spacetime (which has been warped by gravity). One cannot say that matter is affected by gravity whereas light is not, when both are effected and 'bend'.

What do you mean by matter also follows the spacetime ?

[juanrga]

pmb, on 16 April 2012 - 04:55 AM, said:

Physicists understand light to be a form of matter. This viewpoint started with Eintein when he wrote his papers on relativity. For example; in Einstein's 1916 paper which is a review on gravity. In section 14 Einstein writes

I had a rather new undergraduate physics text around here somewhere which defined the term in that way. I can't find it right now. But I know of no valid reason to use the term otherwise. In fact it makes sense to think of the electric field and magnetic field in this way too.

On what basis do you make this assertion?

As shown in the other thread Einstein did many mistakes, his original thinking does not satisfy current scientific standards of rigour and precision (science has advanced a lot of since 1916), and his old quotes do not quality as an argument based in 'authority'.

The standard definition of matter can be found in chemistry and physics textbooks and shows that light is not usually considered a form of matter.

Feynman titled his book "QED: The strange theory of light and matter". Of course, he did not mean the strange theory of matter and matter

This post has been edited by juanrga: 16 April 2012 - 03:27 PM

[pmb]

juanrga, on 16 April 2012 - 03:19 PM, said:

As showed in the other thread Einstein did many mistakes, ...

And I said that everyone makes mistakes so the fact that Einstein made mistakes merely makes him human and nothing else and as such is insufficient reason for you to counter Einstein elsewhere.

juanrga, on 16 April 2012 - 03:19 PM, said:

...his original thinking does not satisfy current scientific standards of rigour and precision, and his old quotes do not quality as an argument based in 'authority'.

I merely quoted Einstein there for historical context, i.e. to show where the viewpoint "light has matter" started. To say that Einstein's thinking does not satisfy current scientific standards of rigour and precision is unjustified.

juanrga, on 16 April 2012 - 03:19 PM, said:

The standard definition of matter can be found in chemistry and physics textbooks and shows that light is not usually considered a form of matter.

The term "matter" is typically a vauge term which is never really defined in chemistry and physics textbooks.

[juanrga]

pmb, on 16 April 2012 - 03:06 PM, said:

What do you mean by matter also follows the spacetime ?

That was my response to morgsboi and it seems evident that I am meaning the same than him when he wrote that "it is the light which follows the space-time". I have tried to state my point using his own wording for improving our communication. I was not trying to be technically precise and accurate.

pmb, on 16 April 2012 - 03:49 PM, said:

And I said that everyone makes mistakes so the fact that Einstein made mistakes merely makes him human and nothing else and as such is insufficient reason for you to counter Einstein elsewhere.

I merely quoted Einstein there for historical context, i.e. to show where the viewpoint "light has matter" started. To say that Einstein's thinking does not satisfy current scientific standards of rigour and precision is unjustified.

The term "matter" is typically a vauge term which is never really defined in chemistry and physics textbooks.

Neither your claim that the term matter is not "defined in chemistry and physics textbooks" nor your deleting of my citation to Feynman book does surprise me, although the definition of the term matter can be found in standard textbooks .

However, your last claim that "matter is typically a vague term" after you initially stated that Einstein understood "light to be a form of matter" deserves some surprise .

[questionposter]

pmb, on 16 April 2012 - 03:49 PM, said:

And I said that everyone makes mistakes so the fact that Einstein made mistakes merely makes him human and nothing else and as such is insufficient reason for you to counter Einstein elsewhere.

I merely quoted Einstein there for historical context, i.e. to show where the viewpoint "light has matter" started. To say that Einstein's thinking does not satisfy current scientific standards of rigour and precision is unjustified.


The term "matter" is typically a vauge term which is never really defined in chemistry and physics textbooks.

Einstein wasn't actually wrong. Both matter and energy distort the fabric of space, and in the newly developing world of quantum field theory, all of this "stuff", both matter and energy, can be described as various types of oscillations in various fields. Both a ball and a light beam are comprised merely of oscillating fields. I suppose it's more like it takes energy to oscillate, and that same energy will cause different oscillations in different fields, like matter fields or light particle fields.

This post has been edited by questionposter: 17 April 2012 - 03:47 AM