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Author Topic:   Speed of Light
New Cat's Eye
Inactive Member

Message 3 of 268 (471929)
06-19-2008 9:50 AM
Reply to: Message 1 by Hoof Hearted
06-19-2008 9:25 AM

I'm not an expert, but one of the concepts I understand is that the speed of light is constant and is independant of the motion of the observer. Why is it then, that red-shift occurs when observing distant galaxies which are moving away from us?

Light doesn't shift red because its speed is changeing. The color of light is dependent on the wavelength (which depends on the frequency). As the source of light moves away from us, the frequency becomes slower which causes the wavelength to appear to be longer, which makes the light look more red. This is the Doppler Effect. You can also read about Red Shift on wikipedia.

This message is a reply to:
 Message 1 by Hoof Hearted, posted 06-19-2008 9:25 AM Hoof Hearted has replied

Replies to this message:
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New Cat's Eye
Inactive Member

Message 74 of 268 (538231)
12-04-2009 5:20 PM
Reply to: Message 73 by Viv Pope
12-04-2009 5:07 PM

light travels
In Message 33 you wrote:

This is because it entails a truly Copernican ‘flipover’ from thinking of light as travelling in space to the opposite logical alternative of thinking of all space and time as being in the light – not light as it is thought of as travelling in space but light as it is actually observed, optically or instrumentally, in its full spectral range.

That we can see an interference pattern when we perform the double slit experiment pretty much destroys that notion that light is not traveling as a wave.

Edited by Catholic Scientist, : appalin' spallin'

This message is a reply to:
 Message 73 by Viv Pope, posted 12-04-2009 5:07 PM Viv Pope has replied

Replies to this message:
 Message 79 by Viv Pope, posted 12-05-2009 5:31 AM New Cat's Eye has replied

New Cat's Eye
Inactive Member

Message 76 of 268 (538235)
12-04-2009 5:45 PM
Reply to: Message 75 by Iblis
12-04-2009 5:33 PM

Re: urgent question
It seemed to me that his main point was that light doesn't travel but instead is everywhere at once... or something like that.

Please excuse me skipping past all the philosophy and geometry whatnot and just asking you straight out: are you asserting that there isn't any photon?

In Message 33 we have this:

Furthermore, if that so-called ‘velocity’ is ascribed to particles of light, as in Einstein’s concept of the ‘photon’, then any idea of that particle being something properly conceived as material becomes untenable. This is because according to Relativity, anything properly called a particle, no matter how small we may be imagine it to be, becomes infinitely massive at the ‘speed c’, whereas the only mass that can be ascribed to a light-quantum in the visible range of the spectrum (i.e., its spectral energy divided by c-squared) is in the minuscule order of 10-35 kilogram.

He seems to misunderstand the whole deal with photons and rest mass and all that.

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New Cat's Eye
Inactive Member

Message 139 of 268 (539241)
12-14-2009 10:54 AM
Reply to: Message 79 by Viv Pope
12-05-2009 5:31 AM

Re: light travels
The well-known fact of what is commonly called ‘wave-interference' does not necessarily imply that there really are waves. The whole thing can be explained in terms of the Feynman-Wheeler theory of direct quantum interresonance between the source-atoms and the screen atoms, something like what David Bohm called ‘quantum potential’.

Oh okay. Then explain it to me.

When I studied the physics of light in college there was an awesome demonstration that I still remember quite well. They had an overhead projector with this wacky aparatus on it. it was a thin clear plasitc set-up of the double slit experiment but it held water in it. There was a little wave maker in the back. You could see the waves on the screen from the projector. So there we had it, right in front of our eyes, water waves interfering and demonstrating constructive and destructive interference. It looked just like this:

Then, they showed us the double slit experiment with light and it produced the well-known interference pattern:

The light behaved just like the water waves except we couldn't actually see the waves themselves when it was done with the light.

But its a great explanation of the observation of the wave-interference. It can be explained in simple english and/or with some diagrams. You don't have to read a whole paper.

If you are serious about this, then please read my conference paper: ‘The Tantalising Two Slit Experiment, Imperial College, 2001. This can be accessed on the POAMS website www.poams.org in the ‘Seminal Publications and Resources’ section, Item 30. It is also dealt with in the books that are mentioned. I’m sure you wouldn’t expect me to write out that whole argument again, here.

The whole argument? No. But I'm definately not going to read your paper. If your explanation has any worth at all, then you should be able to offer a simple consice plain english explanation of the observed phemonemon.

Also, it should be a better explanation that the one of light being propogating waves kinda like water that can so easily be demonstrated.

Spamming your paper to me is not going to convince me that you're on to anything.

Can you explain it or not?

This message is a reply to:
 Message 79 by Viv Pope, posted 12-05-2009 5:31 AM Viv Pope has replied

Replies to this message:
 Message 164 by Viv Pope, posted 12-15-2009 5:21 AM New Cat's Eye has replied

New Cat's Eye
Inactive Member

Message 157 of 268 (539280)
12-14-2009 4:19 PM
Reply to: Message 156 by Son
12-14-2009 4:01 PM

off topic question answered
The first post of Iblis's that I read was really good and I noticed the same thing about his rating too without seein all the low scores. Turns out, most of his messages in the String Theory What is it good for? thread have ratings of 1.

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New Cat's Eye
Inactive Member

Message 167 of 268 (539346)
12-15-2009 10:13 AM
Reply to: Message 164 by Viv Pope
12-15-2009 5:21 AM

Re: light travels
Yes, of course I can explain it.- and have explained it, many times. Don’t you read the posts?

No, I don't read every post. Where's the post where you explained it? You can link directly to it with the msg tags.

ABE: Oh I found Message 34, those 10 reasons. I'll reply to that seperately. ABE: actually, I change my mind see below*

I’m surprised that you can’t see the difference between talking about light-waves in water and light-waves (allegedly) in vacuo.

Well, it was water waves being a demonstration of how light waves propogate.

For instance, what is there to wave in a vacuum?


Are you asking about a medium to propogate through, like the aether or something?

Light waves, themselves, are propogating. They don't need something to progate "in".

We’ve all seen the sort of demonstration you describe. For all their vividness, they say nothing of the LOGIC of this argument about light.

Oh, that "logic" stuff you talking about ain't worth a crap. I've seen the LOGIC that evolution is impossible because of the 1st law of thermodynamics. Its retarded to try to use that LOGIC when a simple observation suggests the complete opposite.

Besides, did you not see – or not read – my posting on the ‘Ten Proofs That Light Doesn’t have a Velocity?’

No, I didn't see it. Post number please (with a link preferably).

‘Spamming my paper to you'? What on earth do you mean by that?

We see guys like you here frequently enough. Your type comes on with some ultimately profound, gonna turn physics on its head, claim but they can never hash out there argument into a text box. The best they can do is throw out links to their website or paper. It might as well be the spam that I get in my email.

Why do I have to convince YOU? I don’t see you as the arbiter on this.

You don't, but this is a discussion forum. Its a two way street. We're not here to play with ourselves. And we're not here to have websites thrown at us (its even in the rules).

Now, if you are unable to explain something in a simple text box, then I don't think you understand it well enough to claim it.

There are many others who are familiar with my work who disagree with you completely.

Until they're here discussing with me, I don't really give a shit about them.

So, if my short explanation doesn’t convince you then please don’t contact me further. From your tone I feel that any further discussion with you would be useless.

Don't run away so soon. At least link me to the posts where you've explained something.

And I'm sorry that being called out on your inability to offer a simple explanation of your claim seems useless to you. That, in itself, is exposing though.

I think Percy hit the nail on the head in the other thread: If anyone thinks that you have explained anything, then they should be able to explain it too. But nobody can, and they're all saying you haven't explianed anything :-\

* I was gonna go point by point to your 10 reasons but I'm not now. I don't see any reason.

I have a direct observation suggesting that light does indeed travel as a propogating wave. All your little logical deductions that light cannot be traveling do not trump my direct observation.

Here's what I had so far:

1. The undeniable fact that c has the dimensions of distance divided by time explains all that is known about the times taken for communications over distance. But the fact that all velocities are distances divided by time by no means entails that all distances divided by time are velocities,

Velocity is defined as "distance over time". You cannot have a "distance over time" that is not a velocity.

which would be as absurd as saying that because all bachelors are men, all men are bachelors.

No, it has nothing to do with Affirming the Consequent.

3. For light to be seen, photographed or detected in any possible way, it has to shine on something. In a vacuum there is, by definition, nothing on which it can shine. So, logically, light cannot be seen, photographed or in any other way be detected in the vacuum of space, which signifies a reduction to absurdity of experiments claiming to have photographed ‘light travelling in vacuo’.

That's actually kind of funny. That once you put the camera in there to take the picture, then you no longer have a vacuum anymore. Well, if you have an emitter, and then a vaccuum, and then a detector, and the light goes from the emitter to the detector, then it must have traveled through the vacuum.

4. To be seen or otherwise detected travelling in a vacuum, light would have to give off light. And that secondary light would have to give off light; and that tertiary light would also have to give off light … and so on, ad infinitum, in a logical regress to absurdity.

Maybe for direct observation, but we can still infer that light is traveling in a vacuum.

5. If c is interpreted as a ‘velocity in the vacuum of space’ (as Einstein’s Second Postulate states), then in a vacuum to what can that ’velocity’ possibly be referred, constant or otherwise? So the concept of light as having a ‘velocity in space’ is just another absurdity.

Actually, I'm not going to bother going through all these.

I'm gonna come at this from another angle. And its the same one I came from earlier.

Regardless of all your LOGIC arguments that light cannot be traveling (which what I've read so far are instead saying that we couldn't directly measure the velocity in a vacuum), I have the direct observation of the two slit expirement that shows that light is, in fact, propogating (traveling) waves. So first, we have the simple explanation that does travel.

Now, you can explain why that is wrong. Or can you?

Edited by Catholic Scientist, : see ABE

Edited by Catholic Scientist, : No reason given.

This message is a reply to:
 Message 164 by Viv Pope, posted 12-15-2009 5:21 AM Viv Pope has replied

Replies to this message:
 Message 168 by Iblis, posted 12-15-2009 12:39 PM New Cat's Eye has taken no action
 Message 176 by Viv Pope, posted 12-16-2009 6:41 AM New Cat's Eye has taken no action

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