I am stunned that a group of variously talented scuba divers could not have settled this question in fewer than 228 pages of posts. What has happened to our education system?
Creation vs. Evolution
- Thread starter Lost_At_Sea
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I solved it back at the begining of Page 3, but these guys are stubborn<G>.
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Godless people.
I did learn some things about Evolution theory reading this..fairly in depth thread actually. Amazed at how much I don't remember from genetics and Biology, to be honest.
Wish someone could explain, via natural selection, why Aussies who have had their tails docked for decades (so the sheperd could tell them from the wolves and shoot the wolves), have now created a bloodline that renders 80% born with tails and 20% without tails. Were the shorter tails selected when the longer tailed dogs were accidently shot?
Petunias and Drosophilia were so much easier.
I did learn some things about Evolution theory reading this..fairly in depth thread actually. Amazed at how much I don't remember from genetics and Biology, to be honest.
Wish someone could explain, via natural selection, why Aussies who have had their tails docked for decades (so the sheperd could tell them from the wolves and shoot the wolves), have now created a bloodline that renders 80% born with tails and 20% without tails. Were the shorter tails selected when the longer tailed dogs were accidently shot?
Petunias and Drosophilia were so much easier.
Oh come now, your theories were completely disproven by 'energy drink lady'
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I forgot about little miss photosythesis. I wonder if she took my advise and if she's reached Wonder Woman status yet?
Soggy:
Maybe I'm misreading this but, the doppler effect that we percieve as a truck, car, train or whatever comes toward us then away from up isn't percieved by light...it's sound. Going one direction the frequency is increasing and the other it's decreasing. The change in frequency can be used to measure speed, which is how the police radar (vascar?) works...only it's both the transmitter and the reciever.
This red shift thing is interesting and I haven't had the chance to read up on it yet but what I have read said that it's similar to the doppler effect.
While we're on the subject I do have some questions though. In regard the the red shift, how are we defining "red"? Are we using a coordinates system like xyz or lab? Or are we talking about a change in wave length that is applied to the whole spectrum? Are we just talking about changes only in wave length or in magnitude also? Color as we percieve it is not only a function of wave length but also of magnitude at the various wave lengths of the spectrum. Of course to measure a "shift" you have to know what the transmitted spectrum is. ie...anything the light passes through will have a filtering effect. I would think that in this case you would have to know exactly what the transmitted spectrum is or the tranfer function of everything the light passes through. Just some questions but I know first hand how touchy color and light measurement can be even in a lab where everything is very tightly controled...though I've been away from it for about a decade now. LOL
The Doppler effect is present in both 'mechanical' waves, those requiring a medium, such as sound, ultrasound etc., and electromagnetic or mediumless waves such as light, radio, microwave etc.
Soggy
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I can't adequately answer all your questions without going back and doing a bit of research.
The Doppler effect applies to waves...sound or light is irrelevent. Police LADAR works off of Doppler, too.
It is the Doppler effect and it's all about ROY G BIV. Take a yellow object in the sky. If it is moving away from us it will look more orange (shifted towards the red). If it is moving towards us, it will look more green (shifted towards the blue).
You bring up some good questions. Among other things, astronomers know of certain standard candles that have known luminosity. Cepheid variables (a type of star) are one of them.
I wish I could answer your questions better off the top of my head, but I can't remember all the details. Reading up on Cepheid Variables might point you in the right direction.
MikeFerrara:
The Doppler effect applies to waves...sound or light is irrelevent. Police LADAR works off of Doppler, too.
It is the Doppler effect and it's all about ROY G BIV. Take a yellow object in the sky. If it is moving away from us it will look more orange (shifted towards the red). If it is moving towards us, it will look more green (shifted towards the blue).
You bring up some good questions. Among other things, astronomers know of certain standard candles that have known luminosity. Cepheid variables (a type of star) are one of them.
I wish I could answer your questions better off the top of my head, but I can't remember all the details. Reading up on Cepheid Variables might point you in the right direction.
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From wiki:
In physics and astronomy, redshift occurs when the visible light from an object is shifted towards the red end of the spectrum. More generally, redshift is defined as an increase in the wavelength of electromagnetic radiation received by a detector compared with the wavelength emitted by the source. This increase in wavelength corresponds to a decrease in the frequency of the electromagnetic radiation. Conversely, a decrease in wavelength is called blueshift.
Any increase in wavelength is called "redshift" even if it occurs in electromagnetic radiation of non-optical wavelengths, such as gamma rays, x-rays and ultraviolet. This nomenclature might be confusing since, at wavelengths longer than red (e.g. infrared, microwaves, and radio waves), redshifts shift the radiation away from the red wavelengths.
Redshift occurs when a light source moves away from an observer, corresponding to the Doppler shift that changes the frequency of sound waves. Although such redshifts have several terrestrial uses (e.g. Doppler radar and radar guns), they are essential in spectroscopic astrophysics to determine the movement of distant astronomical objects. This redshift phenomenon was first predicted and observed in the nineteenth century as scientists began to consider the dynamical implications of the wave-nature of light. Most famously, the spectral redshifts of distant galaxies, quasars, and intergalactic gas clouds are observed to increase proportionally with their distance to the observer. This is generally considered to be significant evidence that the universe is expanding, as predicted by the Big Bang model.
An independent type of redshift results from the time dilation that occurs in general relativity near massive objects, also known as the Einstein effect. This gravitational redshift results only from the assumptions of special relativity and the equivalence principle; the full theory of general relativity is not required.
In physics and astronomy, redshift occurs when the visible light from an object is shifted towards the red end of the spectrum. More generally, redshift is defined as an increase in the wavelength of electromagnetic radiation received by a detector compared with the wavelength emitted by the source. This increase in wavelength corresponds to a decrease in the frequency of the electromagnetic radiation. Conversely, a decrease in wavelength is called blueshift.
Any increase in wavelength is called "redshift" even if it occurs in electromagnetic radiation of non-optical wavelengths, such as gamma rays, x-rays and ultraviolet. This nomenclature might be confusing since, at wavelengths longer than red (e.g. infrared, microwaves, and radio waves), redshifts shift the radiation away from the red wavelengths.
Redshift occurs when a light source moves away from an observer, corresponding to the Doppler shift that changes the frequency of sound waves. Although such redshifts have several terrestrial uses (e.g. Doppler radar and radar guns), they are essential in spectroscopic astrophysics to determine the movement of distant astronomical objects. This redshift phenomenon was first predicted and observed in the nineteenth century as scientists began to consider the dynamical implications of the wave-nature of light. Most famously, the spectral redshifts of distant galaxies, quasars, and intergalactic gas clouds are observed to increase proportionally with their distance to the observer. This is generally considered to be significant evidence that the universe is expanding, as predicted by the Big Bang model.
An independent type of redshift results from the time dilation that occurs in general relativity near massive objects, also known as the Einstein effect. This gravitational redshift results only from the assumptions of special relativity and the equivalence principle; the full theory of general relativity is not required.
Redshifts are measured using 'emission lines'. All elements, because of the energy levels of the electrons surrounding the nucleus, radiate only certain frequencies of light as the electrons give off energy. This light is only radiated in certain energy levels (frequencies of light) and by the pattern of light given off, we can detect what chemicals or elements are glowing, even at a vast distance.
Each element/chemical has its own 'fingerprint'.
The redshift is observed when we recognize that the 'fingerprint' of farther objects are shifted more to the red. We recognize the elements because of the fingerprint (the pattern of frequencies) but all parts of it are shifted a bit to the red or to the blue (for objects approaching).
We notice that some objects are blue-shifted. The Andromeda Galaxy is an example of this, because it is the local group of galaxies and our local galaxies are all orbiting the center of mass of the local group. This is like moths around a flame - where some get closer and some go farther away.
However, as we look to more distant objects, in all directions of the sky, they are all shifted to the red. The farther an object is, the more red the frequency shift of that 'fingerprint'. This is observed for the "more nearby" farther objects - those whose distance can be measured by other means. We can then extend this and observe farther and farther objects, and we note they are redder and redder. At some point we are at distances vast enough that the main method we have to measure the distance is by that redshift. The objects are so far away that redshift is the only method left to use.
Note that these colors are not measured by eye in a "Hey, that looks redder!" manner. The frequency of these emission bands is precisely measured.
Each element/chemical has its own 'fingerprint'.
The redshift is observed when we recognize that the 'fingerprint' of farther objects are shifted more to the red. We recognize the elements because of the fingerprint (the pattern of frequencies) but all parts of it are shifted a bit to the red or to the blue (for objects approaching).
We notice that some objects are blue-shifted. The Andromeda Galaxy is an example of this, because it is the local group of galaxies and our local galaxies are all orbiting the center of mass of the local group. This is like moths around a flame - where some get closer and some go farther away.
However, as we look to more distant objects, in all directions of the sky, they are all shifted to the red. The farther an object is, the more red the frequency shift of that 'fingerprint'. This is observed for the "more nearby" farther objects - those whose distance can be measured by other means. We can then extend this and observe farther and farther objects, and we note they are redder and redder. At some point we are at distances vast enough that the main method we have to measure the distance is by that redshift. The objects are so far away that redshift is the only method left to use.
Note that these colors are not measured by eye in a "Hey, that looks redder!" manner. The frequency of these emission bands is precisely measured.
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