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Thread: What Was The First Color In The Universe?

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    What Was The First Color In The Universe?

    The universe bathes in a sea of light, from the blue-white flickering of young stars to the deep red glow of hydrogen clouds. Beyond the colors seen by human eyes, there are flashes of x-rays and gamma rays, powerful bursts of radio, and the faint, ever-present glow of the cosmic microwave background. The cosmos is …
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    Quote Originally Posted by Universe Today
    Humans don’t see color very accurately. The color we perceive depends not only on the actual color of light but its brightness and whether our eyes are dark-adapted. If we could go back to the period of that first light, we would probably perceive an orange glow similar to firelight.
    No, if we attenuate it enough for comfort with a neutral density filter, we should see it as neutral white, as we do under 3,000K tungsten lights at night. Without attenuation it would be as dazzlingly bright as the filament in an unfrosted bulb.

    Even this color will only last for a time. As large blue stars age and die, only the deep red glow of dwarf stars will remain. Finally, after trillions of years, even their light will fade, and the universe will become a sea of black. All colors fade in time, and time will carry us all into the dark.
    My bold. No, it will be only modestly more orange than the "cosmic latte" swatch. Most M dwarfs emit light that is similar to that of a 3,000K tungsten lamp. Not "deep red" in my understanding of what that expression means.

    I'm sorry but I am seeing a lot of junk writing in Universe Today. Not a majority by any means but too much for comfort.

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    Quote Originally Posted by Article
    After about 10 seconds, the universe entered the photon epoch. Protons and neutrons had cooled into the nuclei of hydrogen and helium, and space was filled with a plasma of nuclei, electrons, and photons. At that time the temperature of the universe was about a billion degrees kelvin. .... But even though there was light, there was not yet color.
    If these photons had time to scatter and exhibit a Planck distribution, as does the eventual CMBR does today, then a color would be observable, if the observer could take a little heat.  When temperatures reach into the millions of degrees, the photon distribution is very heavy in the blue-end of the spectrum, similar to that of our blue sky. The center of the Sun, for instance, should appear a saturated blue if you could peak inside, briefly, very briefly.
    Color is something we can see, or at least some kind of eyes could see. During the photon-epoch temperatures were so high that light couldn’t penetrate the dense plasma. Color wouldn’t appear until the nuclei and electrons cooled enough to bind into atoms.
    I doubt this is correct. Photons could not travel great distances but they did travel very short distances until they encountered all those free electrons. But an observer there – and there was no other place but there – would see a ton of photons only that they would have been scattered just a short distance away from her or him. The high temperatures would still favor a bluish color until it cooled closer to the time atoms formed.
    By then the observable universe was a transparent cosmic cloud of hydrogen and helium 84 million light-years across. By then, all those photons formed in the big bang were finally free to stream through space and time…
    When it first appeared, the universe was much warmer, about 3,000 K. The early universe was filled with a bright warm glow….
    We have a good idea pf what that first color was. The early universe had an almost even temperature throughout, and its light had a distribution of wavelengths known as a blackbody. Many objects get their color from the type of material they are made of, but the color of a blackbody depends only on its temperature. A blackbody at about 3,000 K would have a bright orange-white glow, similar to the warm light of an old 60-watt light bulb.
    1) I think most would describe the color of a light bulb as more yellow-white, unless there is sunlight as background, where the eye will color adjust (ie color constancy) to make sunlight as the white reference source. [I agree with Hornblower in the white description of it.]
    2) Since that was the only light source at the time, the eye-brain (retinex) would adjust this light to appear as white, or near white in color. Camera color processing does something very similar.

    If we could go back to the period of that first light, we would probably perceive an orange glow similar to firelight.
    No, as stated above, it would be the white reference light and it would not lack in intensity, to say the least.
    In 2002 Karl Glazebrook and Ivan Baldry computed the average color from all the light we see from stars and galaxies today to determine the current color of the universe. It turned out to be a pale tan similar to the color of coffee with cream. They named the color cosmic latte.
    IIRC, they had first determined it was turquoise, but revised it. That would’ve been cool. Since most of space is space, not stars, the color in this region would be more blue, if the eye could perceive such low flux levels. This is because of the light scattering (Rayleigh Scattering) from all the gas and tiny dust particles that favor blue light scattering. This is a guess on my part, though. Given enough scattering the color eventually would get to the cosmic latte but opaque clouds may limit this just as our atmosphere’s limited height favors blue and not white (Sun’s color, btw).

    Even this color will only last for a time. As large blue stars age and die, only the deep red glow of dwarf stars will remain. Finally, after trillions of years, even their light will fade, and the universe will become a sea of black. All colors fade in time, and time will carry us all into the dark.
    But by then we will be traveling briskly across the cosmos where SR will blue shift all that is ahead of us.
    We know time flies, we just can't see its wings.

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    Wait- why will be be travelling relativistically in the deep future? It this something to do with the expansion of the universe?

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    Quote Originally Posted by eburacum45 View Post
    Wait- why will be be travelling relativistically in the deep future?
    The faster we go, the sooner we get to wherever we’re goin’. Blueshift color is a consequence; what is too dim or in the infra red, will be bright and blue, Or more violet? My hope is that we get a better handle on time and space to skip through both.

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    George, good catch about the short-distance transparency of the primordial plasma before its transformation into neutral atoms and resulting long-distance clearing. I was already thinking about that, and I have seen references to a mean free path of a centimeter or so in stellar interiors. That is plenty for getting thermalized blackbody light into our eyes or spectrographs in a thought exercise in which we could take the heat. Another fault to find with the article.

    I don't think the light at millions of degrees would be saturated blue. My calculations with the Planck calculator show that with increasing temperature above 30,000K, about the effective temperature of our bluest stars, the ratio of blue to green light asymptotically approaches a limit only modestly bluer than such stars. The same would hold for the ratios of those bands to the red band. It will still be a pastel blue, perhaps resembling sky blue at sea level.

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    Quote Originally Posted by Hornblower View Post
    George, good catch about the short-distance transparency of the primordial plasma before its transformation into neutral atoms and resulting long-distance clearing. I was already thinking about that, and I have seen references to a mean free path of a centimeter or so in stellar interiors. That is plenty for getting thermalized blackbody light into our eyes or spectrographs in a thought exercise in which we could take the heat. Another fault to find with the article.
    The irony is that total darkness makes a poor assumption.

    I don't think the light at millions of degrees would be saturated blue. My calculations with the Planck calculator show that with increasing temperature above 30,000K, about the effective temperature of our bluest stars, the ratio of blue to green light asymptotically approaches a limit only modestly bluer than such stars. The same would hold for the ratios of those bands to the red band. It will still be a pastel blue, perhaps resembling sky blue at sea level.
    I recall attempting to match a sky SED with a Planck distribution. It takes million of degrees to get the slope to ramp-up enough to approach a blue sky SED, but it may be too poor a match to be a saturated blue. It’s been several years but Iclained that the Suns interior would look blue then later saw it mentioned in a subsequent Tyson book. Your take on it would be appreciated. Is there a temp that would give a saturated blue?

    Perhaps a blue Sun thread?

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    Quote Originally Posted by george View Post
    the irony is that total darkness makes a poor assumption.

    I recall attempting to match a sky sed with a planck distribution. It takes million of degrees to get the slope to ramp-up enough to approach a blue sky sed, but it may be too poor a match to be a saturated blue. Itís been several years but iclained that the suns interior would look blue then later saw it mentioned in a subsequent tyson book. Your take on it would be appreciated. Is there a temp that would give a saturated blue?

    Perhaps a blue sun thread?

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    Here is a sample of relative blue, green and red blackbody intensities at various temperatures, as calculated with my Planck calculator. Look how much it changes up to 30,000K, the effective temperature of an "early" B star, and how little it changes above that. These values are normalized to set the green to unity. I ran the calculator up to 3 billion degrees and got no further change in the proportions. It should be noted that in this range the intensity in the visible range is proportional to the temperature across the board. The grand total is proportional to the 4th power of the temperature, but most of it is x-rays and gamma rays at such extremes.

    _______________Wavelength__________
    ___T(K)____400nm____500nm___600nm

    3,000______0.276_____1.00_____1.98
    4,500______0.617_____1.00_____1.17
    5,850______0.851_____1.00_____0.92
    7,500______1.15______1.00_____0.78
    10,000_____1.44______1.00_____0.67
    30,000_____2.12______1.00_____0.53
    300,000____2.41______1.00_____0.49
    3,000,000___2.44______1.00_____0.48

    I stand by my opinion that we will have at most a pale bluish white, only slightly bluer than a B star. A saturated blue would have the green and red bands near zero.

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    Quote Originally Posted by Hornblower View Post
    Here is a sample of relative blue, green and red blackbody intensities at various temperatures, as calculated with my Planck calculator. Look how much it changes up to 30,000K, the effective temperature of an "early" B star, and how little it changes above that. These values are normalized to set the green to unity. I ran the calculator up to 3 billion degrees and got no further change in the proportions. It should be noted that in this range the intensity in the visible range is proportional to the temperature across the board. The grand total is proportional to the 4th power of the temperature, but most of it is x-rays and gamma rays at such extremes.

    _______________Wavelength__________
    ___T(K)____400nm____500nm___600nm

    3,000______0.276_____1.00_____1.98
    4,500______0.617_____1.00_____1.17
    5,850______0.851_____1.00_____0.92
    7,500______1.15______1.00_____0.78
    10,000_____1.44______1.00_____0.67
    30,000_____2.12______1.00_____0.53
    300,000____2.41______1.00_____0.49
    3,000,000___2.44______1.00_____0.48

    I stand by my opinion that we will have at most a pale bluish white, only slightly bluer than a B star. A saturated blue would have the green and red bands near zero.
    Yes, I get the same results as your table. Perhaps, however, that the retinex doesn't require as much blue as we expect it to have. I have failed to achieve a Blue Sky SED I can trust. Unfortunately, after taking the following data, it would argue that an O-class star would be more saturated than a blue sky, which is wrong of course. I used this chart here and I converted it to data to achieve the following graph. It's more upset down, I think, that it should be.

    [Added: See subsequent post to correct this....]
    Click image for larger version. 

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    Last edited by George; 2019-Oct-21 at 06:07 PM.
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    I was right, I was wrong. The blue sky data was erroneous after all.

    This should be right...

    Click image for larger version. 

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    Notice that the intensities are somewhat subtle between 25,000 K and 15 million K, but the 15 million K seems to be a reasonable fit for a saturated blue sky. No?
    We know time flies, we just can't see its wings.

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    Quote Originally Posted by George View Post
    I was right, I was wrong. The blue sky data was erroneous after all.

    This should be right...

    Click image for larger version. 

Name:	Blue Sky II vs Planck temps.jpg 
Views:	13 
Size:	895.4 KB 
ID:	24648

    Notice that the intensities are somewhat subtle between 25,000 K and 15 million K, but the 15 million K seems to be a reasonable fit for a saturated blue sky. No?
    No, I would call it unsaturated. It still has a significant admixture of red through green with it, and it definitely looks paler than the blue emitters in my color TV screen.

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