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Message 12137 - Posted: 17 Jan 2006, 19:26:43 UTC

Based on:
"At the speed of light, time stops."

Ok, time stops; For the photon, relative to the photon.
Yet, it does change. It gets red-shifted.

Although we see a photon as moving at speed x, medium dependant, we say it does not age... at the end of it's trip, that is. (sort-of a trip into the futur.)

Whether the photon travels a meter or 10^99 million kilometers, it would not be able to tell the difference, except if it checks it's red-shift coefficient.

So what is that telling us?
Is it possible to stop the red-shift?
Does red-shift only happen in inter-galactic space?
Would the shift happen if the photon where trapped for 10 milllion years in a project on earth?
- meaning it would require a lack of gravity, or a lesser gravity, to cause the shifting?
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Message 12241 - Posted: 21 Jan 2006, 23:52:29 UTC - in response to Message 12137.  

Photon travel backwards in time? Now i have heard everything.


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Message 12245 - Posted: 22 Jan 2006, 1:32:34 UTC

Now here's my interpretation of red-shift, and this was what I was taught in high school physics:

Red shift is visible when a light emitting source (i.e. a star) is moving away from the view of the detector (i.e. a human) as it elongates the wavelength of the electromagnetic radiation.

As a result, a photon parallel to another photon, both in a vacuum, will see each other at the wavelength they are emitted (imagine they have eyes and can see the photons moving).

Given that time is relative to photons, it is different from another reference point. To say time is constant across the universe would indicate that you were in all places at once.

So:

1) Ok, time stops; For the photon, relative to the photon.
2) Yet, it does change. It gets red-shifted.

A1) Yes, I would agree. Only if the photon was purely observing the other photon. If it observed a different reference frame, then time would change.
A2) This doesnt comply with what I've been taught or any scientific journal I have read. Have a link/reference?

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Message 12251 - Posted: 22 Jan 2006, 2:26:53 UTC - in response to Message 12245.  
Last modified: 22 Jan 2006, 2:30:34 UTC


Red shift is visible when a light emitting source (i.e. a star) is moving away from the view of the detector (i.e. a human) as it elongates the wavelength of the electromagnetic radiation.

I thought it only had to be far away?
- If the light source has to be moving, then I see 2 parts to relativity:
1) The light source is not moving away.
- A photon in this scenario better fits this thread and how I understand(stood) relativity.
2) The light source is moving away.
- This blows away relativity in my eyes, sort-of.

A) But the above is the reason I posted, I have questions. And, it's true that only the speed of light is mentioned in relativity, and not it's make-up/frequency(observed color at destination), when it speaks of light from moving sources.
- You have helped me zero-in on my confusion. Thanks! :)


As a result, a photon parallel to another photon, both in a vacuum, will see each other at the wavelength they are emitted (imagine they have eyes and can see the photons moving).

- just to remove confusion, that also presumes that the photon being watched would be emitting copies of itself in the direction of the watching photon. (otherwise they'd have to cross at right-angles to each other.)


1) Ok, time stops; For the photon, relative to the photon.
A1) Yes, I would agree. Only if the photon was purely observing the other photon. If it observed a different reference frame, then time would change.

- so blue light would see white light, as we do on earth, when it intersected it. Hmm, I'm really trying to make the photon the impossible human travelling at the speed of light, and trying to understand if the brain would be able to process light information. As I understand things, the brain is not aging relative to everything else that it is seeing and should not be able to process the info even though the photon would/could enter the eye.


2) Yet, it does change. It gets red-shifted.
A2) This doesnt comply with what I've been taught or any scientific journal I have read. Have a link/reference?

- I can only repost what you said:
Red shift is visible when a light emitting source (i.e. a star) is moving away from the view of the detector (i.e. a human) as it elongates the wavelength of the electromagnetic radiation.
- So I think we may have a misunderstanding on what I'm trying to get across.
(althought the first point does cover this in a whole new 'light'.)

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Message 12252 - Posted: 22 Jan 2006, 2:28:47 UTC - in response to Message 12241.  

Photon travel backwards in time? Now i have heard everything.


Travelling into the past and staying in the past is different and important to relativity, the way I understand relativity.
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Message 12253 - Posted: 22 Jan 2006, 2:37:36 UTC - in response to Message 12252.  
Last modified: 22 Jan 2006, 2:38:45 UTC

For clarification:

My point here is trying to find how tightly time and space are connected to each other.

Roughly worded:
That, at the speed of light, does all space get covered in one time(instant) and
at the speed of stopped, does one space see all time?

A source is:
http://www.astronomynotes.com/relativity/s1.htm
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Message 12267 - Posted: 22 Jan 2006, 15:35:29 UTC - in response to Message 12253.  

For clarification:

My point here is trying to find how tightly time and space are connected to each other.

Roughly worded:
That, at the speed of light, does all space get covered in one time(instant) and
at the speed of stopped, does one space see all time?

A source is:
http://www.astronomynotes.com/relativity/s1.htm


From that site:


Since the laws of physics do not depend on your location or motion, Einstein reasoned that the speed of light will be measured to be the same by any two observers regardless of their velocity relative to each other. For example, if one observer is in a rocket moving toward another person at half the speed of light and both observers measure the speed of a beam of light emitted by the rocket, the person at rest will get the same value the person in the rocket ship measures (about 300,000 kilometers/second) instead of 1.5 times the speed of light (=rocket speed + speed of beam of light). This assumption has now been shown to be correct in many experiments. To get the same value of the speed (= distance/time) of light, the two observers moving with respect to each other would not only disagree on the distance the light travelled as Newton said, they would also disagree on the time it took.

Einstein found that what you measure for length, time, and mass depends on your motion relative to a chosen frame of reference. Everything is in motion. As you sit in your seat, you are actually in motion around the center of the Earth because of the rapid rotation of the Earth on its axis. The Earth is in motion around the Sun, the Sun is in orbit around the center of our Galaxy, the Galaxy is moving toward a large group of galaxies, etc. When you say something has a velocity, you are measuring its change of position relative to some reference point which may itself be in motion. All motion is relative to a chosen frame of reference. That is what the word ``relativity'' means in Einstein's Relativity theories. The only way observers in motion relative to each other can measure a single light ray to travel the same distance in the same amount of time relative to their own reference frames is if their ``meters'' are different and their ``seconds'' are different! [b]Seconds and meters are relative quantities. [b]


The fact that as you approach the speed of light, not only does time change, but distance changes exponentially.

This is assuming you mean 'space' as 'distance' - I define space as being that black stuff around the planets and stuff!

Dont forget there are two types of relativity: 'Special Relativity' and 'General Relativity'. Under General Relativity, Einstein concluded that gravity = acceleration: http://www.astronomynotes.com/relativity/s3.htm . Actually that page has good explanation of space-time :D
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Message 12268 - Posted: 22 Jan 2006, 15:38:16 UTC - in response to Message 12253.  

Also, with regards to redshift:



Prediction: light escaping from a large mass should lose energy---the wavelength must increase since the speed of light is constant. Stronger surface gravity produces a greater increase in the wavelength.

This is a consequence of time dilation. Suppose person A on the massive object decides to send light of a specific frequency f to person B all of the time. So every second, f wave crests leave person A. The same wave crests are received by person B in an interval of time interval of (1+z) seconds. He receives the waves at a frequency of f/(1+z). Remember that the speed of light c = (the frequency f) × (the wavelength l). If the frequency is reduced by (1+z) times, the wavelength must INcrease by (1+z) times: lat B = (1+z) × lat A. In the doppler effect, this lengthening of the wavelength is called a redshift. For gravity, the effect is called a gravitational redshift.

Observation: spectral lines from the top layer of white dwarfs are significantly shifted by an amount predicted for compact solar-mass objects. The white dwarf must be in a binary system with a main sequence companion so that the amount the total shift due to the ordinary doppler effect can be determined and subtracted out. Inside a black hole's event horizon, light is redshifted to an infinitely long wavelength.



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Message 12323 - Posted: 23 Jan 2006, 19:14:42 UTC - in response to Message 12268.  

well, I always understood it as the fact that light is in space, which is expanding, as to why it gets expanded/stretched.

I like the gravity factor much more!
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Message 12324 - Posted: 23 Jan 2006, 19:19:18 UTC - in response to Message 12323.  
Last modified: 23 Jan 2006, 19:26:21 UTC

from the link you posted, I also understand better, and prefer, that earth is held in place around the sun because it is the shortest path created by the sun's gravity effect on the surrounding space/time rather than trying to picture a 'string' of pull on the earth.

addit:
To expand that view, I'd like to understand better the breakup of comet levi9 around jupiter, and see if it brokeup in a way that:
1) looked like it was pulled apart due to uneven pull, or
2) looked like it was squished apart, like an egg in your hand, because parts of it were in a smaller and smaller space faster than the comet bits could react to the change.

addit:
- as an egg would be squished in the middle, in your hand, the center bits would fly out ahead of the leading bits(shell), whereas a comet has it's leading edges progressively squished.
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