🚀 go-pugleaf

On Mar 27, 8:51 am, PD <TheDraperFam...@gmail.com> wrote:
> On Mar 27, 8:08 am, kenseto <kens...@erinet.com> wrote:
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> > On Mar 26, 4:00 pm, PD <TheDraperFam...@gmail.com> wrote:
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> > > On Mar 26, 3:18 pm, kenseto <kens...@erinet.com> wrote:
>
> > > > On Mar 26, 12:45 pm, PD <TheDraperFam...@gmail.com> wrote:
>
>
> > > Yes. Take a paper towel tube without any lens and point it at the sky.
> > > Now take a soda straw and point it at the sky. There is nothing in the
> > > hole of the paper towel tube or a soda straw that can generate a new
> > > source. Such an arrangement is perfectly suitable for a diffraction
> > > grating.

There is the air in the hole of the paper towel tube that acts as the
source.

>
> > Ah....so you are saying that the astronomers are using straws to make
> > diffraction grating readings?
>
> No, but those astronomers have learned that adding a lens does not
> change the diffraction pattern or the measured wavelengths, because
> they've done that lab. See below. (Ken, read first, then talk second.)

The air or the lens act as a light source. So you see the incoming
light is a new light source after all. :-)

>
> > > Now, if you like, you can then *add* a lens to the paper towel tube to
> > > collect more light.
>
> > Bingo the lens acts as a new source in the observer's frame.
>
> No, it doesn't do anything of the kind. See below. (Read first, talk
> second.)

Yes it does.

> > >If you actually do that experiment, you'll find
> > > that adding the lens does not change the measured wavelength at all.
>
> > How do you know? Did you first using straw to make measurement and
> > then add lens to the straw?
>
> YES! Read the paragraph below. This is done as an exercise in freshman
> labs all the time. I know this is the case because I've DONE it, and
> students in the labs for the classes I've taught have done it, and
> they've seen it too. And astronomers know it's true, because they did
> the same exercise when they were students and were learning about
> spectroscopy. And you should do it too, so that you don't make stupid
> statements like this. You have so many excellent universities within
> an hour's drive of your house, and it would take 4 months to bring you
> up to speed on so many things you simply don't know anything about.

But you failed to realize that any measurement by the grating is a
measurement of the wavelength for a source at rest in its frame.
>
>
>
> > > This may come as a shock to you, but that is a simple test that is
> > > done in freshman physics labs across the country every semester. Had
> > > you actually done that lab at some point (and I would have thought you
> > > did), then you would not be making the ridiculous statements you've
> > > been making about the telescope being a new light source and altering
> > > the wavelength.
>
> > Sigh....I didn't say that the lens is altering the wavelength. I said
> > that the lens is a new light source in the observer's frame
> > and the
> > grating measures the wavelength coming from it.
>
> But the measured wavelength is IDENTICAL to the wavelength coming
> through a HOLE. A hole cannot become a new light source, any more than
> holding up your hands and making a picture frame with your fingers and
> thumbs will make your hands a new light source for the starlight
> coming through that. If the wavelength is IDENTICAL between a case
> with a lens and a case with just a plain hole, then what you are
> saying is stupid. Think about it again.

That is irrelevant. The grating will define a new wavelength for any
source at rest wrt it.

>
> > Light from the lens is
> > like light from a sodium source or hydrogen source at rest wrt the
> > grating.
>

>
> > > > I know that it is the pattern that determines the source. But once the
> > > > source is determined the the speed of the incoming light can be
> > > > calculated as follows:
> > > > c'= (measured frequency)(universal wavelength of the source)
>
> > > That is substituting a wavelength for that source that does not BELONG
> > > to that source.
>
> > No that's doing physics the logical way. Remember the example I gave
> > you:
> > 1. There is a constant water wave in a pond with a frequency of
> > N waves/second and the wavelength is L meter.
> > 2. You are at rest wrt the source of the wave so thew arriving speed
> > of the waves is L*N meters/second.
> > 3. You are swimming toward the source. The arrival rate of the waves
> > is (N+n) and the wavelength remains constant L.Therefore the speed of
> > arrival of the waves is L(N+n) meters/second
> > 4. You are swimming away from the source. The arrival rate of the
> > waves is (N-n)/second and the wavelength remains L meters. Therefore
> > the arrival speed of the wave is L(N-n) meters/second.
>
> Sorry, light is KNOWN to be NOT LIKE water. It does NOT behave the
> same way as water. Repeating the error does not make it right. It is
> *measured* to be different. Saying it is still the same when it is
> *measured* to be different is not logic. It is lunacy.

Your statement is based on the bogus assumption that the speed of the
incoming light is a constant c. Light wave is like water wave if the
universal wavelength of the source is used to determine its arriving
speed.
>
>
>
> > >You are removing the *measured* wavelength, and
> > > replacing it with a wavelength that applies to a *stationary* source.
>
> > The measured wavelength is the wavelength of a new source at rest wrt
> > the grating. This wavelength is used to determine the original source
> > of the incoming light.
>
> There is no new source.

Sure there is new source. Every source the grating measures is a new
source in its frame.....including the incoming light.
>

Ken Seto