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  • Why in space red light travels farther and is more observed in dying stars before a star becomes a black hole?

while on Earth in water and air the blue light travels the farthest. For example: a T.V. looks blue from a distance.

  • Is red light lighter than blue light therefore red photons travels faster escaping gravity, but is also absorbed easier by matter and blue light is absorbed by subatomic matter more than red light?
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    $\begingroup$ Are you talking about the doppler effect? $\endgroup$ – PyRulez Jan 11 '16 at 4:40
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    $\begingroup$ Take a look at en.wikipedia.org/wiki/Relativistic_Doppler_effect $\endgroup$ – PyRulez Jan 11 '16 at 4:42
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    $\begingroup$ in the vacuum, no photon is faster than another, definitively $\endgroup$ – user46925 Jan 11 '16 at 4:49
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    $\begingroup$ @Jen The reason dying stars are red and the sky is blue is completely unrelated. It has nothing to do with speed or gravity (in this context). $\endgroup$ – PyRulez Jan 11 '16 at 4:54
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    $\begingroup$ @Jen I don't know what are partials traveling in waves and light partials ... Light takes the shortest path ... another thing : when supernovae explosion light is received on telescopes, all the frequencies come together, after million of ly ! $\endgroup$ – user46925 Jan 11 '16 at 5:15
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There are several different things that need to be explained / explored here.

First - the speed of light in vacuum is independent of frequency / wavelength. The same is not necessarily true for light in any medium other than vacuum: this is why we can see rainbows!

Second - not all objects emit "white" light. The emission spectrum of a star depends, among other things, on its temperature and composition. If the emission is mostly due to the temperature of the start, then you get black body radiation (yes, a black body can look white, red, yellow...). The black body radiation of an object depends on its temperature - the hotter it is, the more radiation there will be, and the more the spectrum shifts towards blue. If a star runs out of fuel but is not massive enough to become a supernova, it may become a red giant instead - big, "cold", red. The emission spectrum of a star may be further modified by the presence of certain atomic species - this can give rise to absorption or emission peaks in the otherwise smooth black body spectrum.

Third - if an object is moving towards the observer, the frequency of light observed will increase (blue shift); when it is moving away, you get red shift. Since the universe is expanding, objects that are far away exhibit greater red shift.

Fourth - as light travels through space, it will interact with (and be absorbed by) interstellar dust. The density may be very low, but when you have a long way to travel, it can add up. Actually, this is how NASA looks for potential stars-with-planets: if planets can form around a star, there is usually a lot of dust near that star; this dust will absorb some of the light from the star, and may re-emit it. But since the dust is much cooler than the star, this will change the spectrum towards the red (cooler).

Fifth - there is a particular mechanism for light scattering called Rayleigh scatter. The probability of light being scattered by a small particle is related to the size of the particle relative to the wavelength of the light - the shorter the wavelength, the stronger the scatter. This has two noticeable effects on earth: the sky is blue, and the sunset is red. That's really the same physics giving rise to different colors! When the sun is close to the horizon, the sunlight has to travel through a lot of the atmosphere to get to your eye. This means it will encounter a lot of small particles in the air, and that means that a lot of the blue light in the sunlight has a chance of being scattered. If you starts with all the colors and you scatter the blue, you are left with something that looks reddish. At the same time, the sky is blue because if you are not looking directly at the sun, then you are normally looking at "the black of space". Except that there is atmosphere in the way, and little particles in the atmosphere can give rise to scatter of sunlight (during the day). And since the most likely (visible) color to scatter is blue, this makes the sky blue.

Sixth - the perception of color. When you look at an object, it is really hard to know what color it is. Instead, you tend to judge the color based on what is nearby. When you are indoors, and the incandescent (tungsten) light is on, a piece of white paper will look "white" to you. If you use a different light source (say the sun light), the paper will still look white. But in fact it will be a very different color! Digital cameras can really show you this - they use something called "White Balance" to try to correct for the color of the light, but if you don't do that, an indoor photo will look very yellow. In the "olden days" of color film, you would use a special "tungsten filter" on your camera to correct for the yellow color; otherwise your photos would look horrible. And this explains your TV. If you are close to a TV, it looks bright, and white is white. As you walk further away, you see other things that are more yellow (because they are illuminated with incandescent light). By comparison, the "white" from the TV will look blue.

I wrote an earlier answer about the "color" of the moon; in that, I created a simple grayscale image that shows how our perception of one shade depends on what else we see. While it was not designed to demonstrate the "white is blue" thing, it might be instructive:

enter image description here

It is reasonable to say that the little rectangle on the left looks white, while it looks gray on the right; and whether you consider it gray or white in the middle depends on your screen brightness, probably. But they are in fact all the exact same shade of gray.

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    $\begingroup$ Perhaps it would be helpful to add a picture to illustrate point six: i.stack.imgur.com/pxyP0.jpg $\endgroup$ – user1717828 Jan 11 '16 at 5:38
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    $\begingroup$ @user1717828 - please, not The Dress!!! $\endgroup$ – Floris Jan 11 '16 at 5:42
  • $\begingroup$ @floris The dress and squares is an illusion caused by the angle if the screen. It doesn't work on older TV like screens. $\endgroup$ – Muze the good Troll. Jan 11 '16 at 6:53
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    $\begingroup$ @Jen "illusion" and "perception" are closely intertwined. The fact that our eyes adjust our perception of "white" is based on sound science. It does not depend on the age of a television. Whether the TV looks more blue from a distance does depend on the lighting used and the color temperature of the screen (most modern computer displays allow you to adjust color temperature - making white more yellow or more blue) $\endgroup$ – Floris Jan 11 '16 at 15:20
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No color light travels farther or faster than any other light in a vacuum, the television room, water or anywhere else except very special or very large environments.

Like you suggest, if the intergalactic space between supernovae absorbs red light differently than blue light, or vice versa, that will affect which we detect here on earth (hopefully an astro guy/girl can come along and weigh in with specifics here). Other than that, nothing in your question really holds true.

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    $\begingroup$ @Jen, I can't say I've ever noticed that, but I am confident if you have seen that it is not based in fundamental physics. $\endgroup$ – user1717828 Jan 11 '16 at 5:33
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    $\begingroup$ See the edit to my answer (point 6) for a plausible explanation $\endgroup$ – Floris Jan 11 '16 at 5:34
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    $\begingroup$ @user1717828 - it is dangerous (and somewhat unchivalrous) to attribute a downvote to a particular user. Looking at her stats, Jen has made a total of 3 downvotes in her entire career on this site... Chances are low you were one of them. $\endgroup$ – Floris Jan 11 '16 at 5:37
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    $\begingroup$ "No color light travels [...] faster than any other light in [...] water" -- this is simply wrong. $\endgroup$ – Norbert Schuch Jan 12 '16 at 8:43
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    $\begingroup$ @NorbertSchuch, OP's question asks about light getting measurably bluer as it travels from the TV to her eyeball. In the context of answering her question, I think the simplicity of my statement outweighs the benefits of being exactly correct. If you think you can improve it without talking over the intended audience, please edit the answer. $\endgroup$ – user1717828 Jan 12 '16 at 9:03

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