How is redshift measured?

"OG" wrote in message
...

"Ed and Kathy Hannig" wrote in message
m...
Didn't I read something within the past several years about light being
affected by the sun's gravity? And if I'm not mistaken there are
instances
of galaxies being magnified due to gravitational lens in space.


Yup, but this is not the same as radio waves following the curvature of
the
earth.

Light certainly is affected by gravity, but the effects are very small.
In
1919, Eddington measured a very slight bending of light of a star as it
passed the sun during a total eclipse; this confirmed a prediction made by
Einstein's General Relativity theory. A google search for eddington
eclipse will bring a number of references.

More recently, gravitational lensing has been detected where light from a
distant galaxy is bent around a galaxy closer to us, giving multiple and
distorted images (similar to what is seen through old 'bottle' glass
panes).
Do a google search for einstein's cross .

An important point to note with both of these is that the effect is very
small. The bending is measured in tiny fractions of a degree.

It is true that there is a small gravitational effect on light giving rise
to a red shift, but this is also very small. The correlation between
galactic redshift and distance has been measured and seems to be
consistent
with the 'recession' model. Alternative causes have been proposed, tested
and explored, but have not been broadly accepted. So far, the expanding
universe model seems to be the best bet.

Hope this helps.

It might be instructive to point out that while the deflection of starlight
is very small, that isn't something due to the nature of light. The
accelleration of light in a gravity field is the same for light as it is for
a cannon ball in feet per second. However, the light isn't sticking around
long enough to "fall" very far.

It goes back to classical physics where you have two rifles parallel to the
ground. One rifle has twice the powder (muzzle velocity) of the other. Fired
simutaneously, both bullets strike the ground at the same time, but one
strikes twice as far down range. The one traveling fastest does have a
flatter curve. None the less, its feet per second downward was the same as
the other- the reason why they both struck at the same time. So while it
might be tempting to say one was more effected by gravity then the other, it
just isn't so.

"OG" wrote in message
...

"AngleWyrm" wrote in message
news:_SKOb.83971$5V2.110779@attbi_s53...
"OG" wrote in message
...

No, it's hard to convey at this level, but the bending of light is not
dependent on light having mass (and hence a gravitational attraction
towards
the sun). The bending of light is due to the 'grid lines' of space
itself
being distorted by masses like the sun and planets.

Ok so let's say space is bent by the stuff in it, and thus trajectories
are
bent as well.
How do we measure this bending effect of space?

I'm not aware it's measured directly, but in principle one could take 3
widely separated satellites and simply measure the angles between them. In
the vicinity of a gravitating mass, the angles won't add up to exactly 180
degrees. This is the exact definition of a 'curved space'.

In practice, I'm not aware that this has been done directly (once again
the
angles are very small); but the curvature of space allows us to calculate
the theoretical rate of precession of the orbit of Mercury. This matches
the
observed rate that had been otherwise inexplicable.

The GPS system must take into account Einstein's relativity. I've been given
to understand that if it did not the errors in position would be in the
hundreds of feet. The military wouldn't like that. Not sure if this is the
first time the practical significance of relativity has reared its head, but
obviously it is a very important one.



Does this come to the same thing as adding vectors for trajectory +
gravity?

Sorry, I couldn't tell you.

I'd suggest you get a book that you can read and re-read - this isn't
something to pick up from scratch in a format like this!

The red shift is measured by our brain. Our brain sees Blue or red,
light rays and knows the reason what these two colors(waves) represent
Bert.

CeeBee:

CeeBee wrote:

snip
Redshift is measured by shift of absorbtion lines in a spectrum caused by
elements.



The Apparent Red Shift is the graphic pattern of the spectral emission
lines of photons of various energy levels emitted by atoms, or
frequencies of emitted photons, caused by the refraction of the photons
through a prism (or other device), which photons originate from various
elements and are refracted differently according to the energy levels,
or frequencies, of the photons, and which element patterns of various
emitters are compared according to their positions on the spectrograph.

The refracted photon quantity lines of a given element may appear to be
shifted to the left or right in the spectrographs of different element
photon sources.

No concept of the expansion of the universe or the BB is implied by the
Apparent Red Shift.

The lines represent the quantities of photons that are emitted,
modified, received and displayed in the spectrograph. Emission
spectrographs refer to the numbers of photons emitted at each frequency.
Absorption spectrographs refer to the numbers of photons absorbed by, or
combined with, interceding atoms or electrons at each frequency
according to the properties of the masking atoms.

Ralph Hertle

CeeBee wrote:

Ralph Hertle wrote in alt.astronomy:

CeeBee wrote:

Redshift is measured by shift of absorbtion lines in a spectrum
caused by elements.

The Apparent Red Shift is the graphic pattern of the spectral emission
lines of photons of various energy levels emitted by atoms, or
frequencies of emitted photons, caused by the refraction of the
photons through a prism (or other device), which photons originate
from various elements and are refracted differently according to the
energy levels, or frequencies, of the photons, and which element
patterns of various emitters are compared according to their positions
on the spectrograph.

It's a damn nifty way to say the same



CeeBee:

You left out the particularizing concepts that differentiate or separate
the concept of the Apparent Red Shift from all other concepts. When you
say, "the same", do you mean that YOUR idea of that classification is
the same as all other ideas within the same classification?

Nonetheless, your idea, as you state it, is not the same as my idea as I
state mine. You simply need to be more specific.

Thanks for the complement, however.

Ralph Hertle.

CeeBee:


CeeBee wrote:

(G=EMC^2 Glazier) wrote in alt.astronomy:


The red shift is measured by our brain. Our brain sees Blue or red,
light rays and knows the reason what these two colors(waves) represent
Bert.



Redshift is measured by shift of absorbtion lines in a spectrum caused by
elements.





There is more to it than that. Photons may be absorbed in the distant
object, in the nearby galaxy materials of dust, hydrogen, and subatomic
particles, for example, in the occlusive stuff in intergalaxial or
interstellar space, by the Earth's atmosphere and dust, and by the glass
prism.

At the same time the transmission spectra for transparent materials and
gasses, dichroic reflection spectra, backscatter spectra, and prism
refraction spectra may also block or modify light or light spectral
characteristics; and these events can occur at various places along the
trajectory of the photon.

There is, of course, the initial emission spectra of the several
elements or materials that produce the photons that are ultimately
transmitted and received.

I suspect that the energy levels of the hydrogen gas and electrons in
space may modify the various discrete frequencies of the transmitted
spectra. I haven't seen studies of that, however, since electrons
function in quite different ways at different electron energy levels, it
may be supposed that the colliding photons of the aforementioned spectra
may be modified in some way.

Gravitational bending may produce changes in the spectral element lines
due to refraction or collisions, but I have no direct knowledge of that.

Spectral characteristics may also be changed by collision and
re-radiation, either elastic or inelastic, and there may be secondary
products emitted as well. If the photon loses energy and it is not all
absorbed by the second entity of collision there may be a product that
is a radiated result. That's all guesswork, and I base that on a number
of 'what if' scenarios and scientist's works in physics.

How the numerous causes for what we observe to be identified could ever
be sorted out by the scientists, I don't know. That work does seem to me
to be one of the great challenges of science. Just to win a piece of
that knowledge would be great fun.

One discovery that could be made could be that the electromagnetic
spectrum is not continuous. It may be that the source of photons can
only produce certain frequency photons under specific conditions, and
that all sources in the universe may not have all frequencies on the
mathematical continuous spectrum covered. There may be some gaps, and
the properties of the source entities and all other intervening entities
may govern the specific natures of the photons produced. Scientific
apparatus may be able to create some ranges of frequencies, but
ultimately the properties of the entities in the universe or the
apparatus will govern. My immediate guess is that according to their
properties materials are energized to produce discrete photon radiation,
and that the continuous EM frequency scale is merely a mathematical
measuring device.

Ralph Hertle