Tired-light and slowed-light

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by mhelland</i>
<br />no tired-light models actually postulate that the photon slows down, just that is looses energy. Is that correct?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Yes. The speed of a wave cannot be changed except by changing the properties of the medium it propagates through. But energy loss can occur through simple friction with some other medium. For example, ocean waves might gain or lose energy from interaction with winds.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Have you personally considered the possibility that the photon actually looses speed?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Yes. But I have never found a way to provide a physical mechanism and work that into a sensible model of the universe, especially an infinite universe (as the Meta Model and certain lines of logic seem to require).

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">This would be pretty simple to test. Its a falsifable hypothesis. Measure the speed of light coming from very distant galaxies. This hypothesis predicts that it will be less than c.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">Yes, it is testable, and has in fact been tested. A team led by Bill Baum in the late 1960s or early 1970s did a measurement of the speed of light from a distant quasar by measuring the energy at a given wavelength, and found it to be the same as for laboratory photons. Unfortunately, I don't have a specific citation to the experiment because I wasn't keeping track of references that far back. But if an internet search doesn't turn it up, it at least appeared as an abstract in the Bulletin of the American Astronomical Society, and could be searched for there.

You are correct that "tired light" involves no speed change, just energy. It will probably help you to sort things out if you start thinking of "lightwaves" instead of "photons" because ballistic entities cannot have a "wavelength", so some of the properties of waves need not apply. But real light definitely has all wave properties, without exception. It also has two properties (Photoelectric effect; Compton effect) normally associated with particles, but these have wave explanations too; whereas light has no uniquely particle-like property.

Once you start thinking "waves", you will need to think in terms of a medium, and the model constraints and ways to test hypotheses will quickly follow. -|Tom|-

Tom and mhelland,

Interesting ideas here and a very good question. I too have wondered similar and my conclusion was and is that if waves slowed due to travel over the same density of medium we could likely never be able to be sure enough of the purity of any medium or produce a manageable length of it for a valid test. Also I would like to know Tom if you recall any details as to the methods of the test such as the site of the collection. Taken on the ground or in space? A measure from the surface of the planet would to my mind ‘of course’ produce identical results to any other measures of light taken within our surface atmosphere. Should there not be a difference between the speed of light in 1000 MB of air and the speed in the much less dense medium of space? For that matter can we really know what the speed of light is in an actual total vacuum? This is given that you accept the more recent idea of many (based on recent evidence) that at least diffuse hydrogen exists at all locations within our solar system and likely our galaxy and beyond.

Looking forward to your response,

Leland


There is only one kind of stuff!

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by Leland</i>
<br />I would like to know Tom if you recall any details as to the methods of the test such as the site of the collection. Taken on the ground or in space?<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">After 30+ years, I don't recall many detals. I think it was conducted at the University of Arizona.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">A measure from the surface of the planet would to my mind ‘of course’ produce identical results to any other measures of light taken within our surface atmosphere.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">If a photon (lightwave) was already slowed when it reached the top of our atmosphere, it certainly would not speed up again in air.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Should there not be a difference between the speed of light in 1000 MB of air and the speed in the much less dense medium of space? For that matter can we really know what the speed of light is in an actual total vacuum? This is given that you accept the more recent idea of many (based on recent evidence) that at least diffuse hydrogen exists at all locations within our solar system and likely our galaxy and beyond.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">This gets into the theory of light propagation. According to Feynman, light always propagates at speed c. The reason it appears to go slower in atmosphere or glass or intergalactic hydrogen is because the photons (lightwaves) are being continually absorbed by matter, then re-emitted. This process introduces a delay, typically about 10 nanoseconds per absorption/re-emission. But between atoms, the speed is the same as in a vacuum. -|Tom|-

&gt;If a photon (lightwave) was already slowed when it reached the top of our atmosphere, it certainly would not speed up again in air.

Tom, quantum electrodynamics casts some doubt on your assertion here.

In QED photons are aborbed and emitted by electrons. If this happened to the photons we were measuring, it is quite possible the photon absorbed by electrons in the atmosphere could be moving slower than c, and the photon re-emitted could be moving at c again.

I detailed this control in the experiment I described and linked to on sci.physics.research.

I would not rule out such claims if I were you, unless you have more insight to QED than I.

mhelland@techmocracy.net

PS:

&gt;According to Feynman, light always propagates at speed c.

That's not true either. In QED there are amplitudes for photons that allow them to travel slower and faster than c. Here is a quote from Feynman:

"It may surprise you that there is an amplitude for a photon to go at
speeds faster or slower than the conventional speed, c. The amplitudes
for these possibilities are very small compared to the contribution
from speed c; in fact, they cancel out when light travels over long
distances. However, when the distances are short...these other
posibilities become vitally important and must be considered."

mhelland@techmocracy.net

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by mhelland</i>
<br />In QED photons are aborbed and emitted by electrons. If this happened to the photons we were measuring, it is quite possible the photon absorbed by electrons in the atmosphere could be moving slower than c, and the photon re-emitted could be moving at c again.<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote"> Then it is pointless to hypothesize a speed of light slower than c because every photon from distant sources is absorbed and re-emitted by intergalactic hydrogen, and must therefore have the same speed.

My answer was given in the context of the question: a proposed change in the speed of light sustained even after such ever-present absorption events.

<blockquote id="quote"><font size="2" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">Here is a quote from Feynman: "It may surprise you that there is an amplitude for a photon to go at speeds faster or slower than the conventional speed, c. The amplitudes for these possibilities are very small compared to the contribution from speed c; in fact, they cancel out when light travels over long distances. However, when the distances are short...these other posibilities become vitally important and must be considered."<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">But the question again presupposed long distances, not short ones. In this context, "short" must mean "between absorptions", which is probably a fraction of a centimeter in air. So why raise an irrelevant point as if it were an objection? -|Tom|-