What *would* the night sky look like if we could see the entire EM spectrum?

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Discussion Overview

The discussion explores the hypothetical appearance of the night sky if it were possible to perceive the entire electromagnetic spectrum, beyond the visible range. Participants consider the implications for astronomy, color perception, and the representation of various wavelengths.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that if color perception were rescaled to include all wavelengths, the night sky would look similar to the visible spectrum, with some additional radiation at both ends.
  • Others argue that images combining different wavelengths, such as visible, infrared, and x-ray, show a significantly different appearance than what is visible alone.
  • A participant mentions the challenge of conceiving what non-visible wavelengths would look like, suggesting that images representing these wavelengths would need to be shifted into the visible spectrum for comprehension.
  • Another participant expresses uncertainty about the average spectrum of the night sky, speculating that it would peak in the visible range due to the nature of stellar radiation.
  • Some participants emphasize that the differences in frequency domains are substantial, which justifies the development of various telescopes for astronomical observation.
  • One participant presents an example of how Jupiter might appear if magnetic fields were visible, indicating the potential for dramatic differences in appearance.
  • Another participant seeks to understand what the night sky would look like if the visible spectrum were expanded to include wavelengths outside the typical range, suggesting that most matter would appear greenish.

Areas of Agreement / Disagreement

Participants express differing views on whether the night sky would appear dramatically different when considering the entire electromagnetic spectrum. Some assert that significant differences exist, while others suggest that the overall appearance may not change drastically. The discussion remains unresolved regarding the exact nature of these differences.

Contextual Notes

Participants note limitations in their understanding of the average spectrum and the challenges in visualizing non-visible wavelengths. There is also mention of the dependence on definitions of color perception and the conditions under which images are created.

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Assuming, of course, that we simply rescaled our color perspectives so that longest wavelengths = red, shortest wavelengths = violet. Are there any such pictures?
 
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Not altogether unlike what we see in the visible spectrum. There is a bit more radiation at both ends, but, it does not make a dramatic difference.
 
You can no more conceive this than you can describe colour to a blind person. Any pictures we create of this would look the same to you as pictures that didn't include these wavelengths because you can't see them.

Any pictures that show wavelengths like x-ray can only do so if they are shifted into the visible spectrum.
 
Any pictures that show wavelengths like x-ray can only do so if they are shifted into the visible spectrum.

But that is what the OP suggested...
 
mr. vodka said:
But that is what the OP suggested...

My mistake. I read colour perception as meaning biologically changing rather than chaining the image.
 
I actually dug around for a night-sky-average spectrum in absolute units over many decades of wavelength, but couldn't find one so I don't know. But I would bet it would peak in the visible just like the spectrum that our eyes detect does, because most radiation comes from stars that have an effective blackbody spectrum that peaks in the visible. You would get a lot more "blue" from UV up through x-rays (variety of sources), and also a lot more "red" from warm dust down to the cosmic microwave background, but plotted in units like Ergs/s/eV/Sr I would bet it still peaks in the visible.
 
Chronos said:
Not altogether unlike what we see in the visible spectrum. There is a bit more radiation at both ends, but, it does not make a dramatic difference.
I beg to differ. That what we see in different frequency domains is dramatically different from what we see in the visible spectrum is the driving impetus behind the many different kinds of telescopes astronomers have developed. Astronomers use telescopes that range from long wave radio up to gammas. If what we saw was more or less the same across the EM spectrum there would be little justification for this plethora of devices, some of which are very expensive.
 
Whether it already exists or not: is there any reason to suspect the picture that the OP suggests can't actually be made? I think that would be a very interesting picture :)
 
  • #10
D H said:
I beg to differ. That what we see in different frequency domains is dramatically different from what we see in the visible spectrum is the driving impetus behind the many different kinds of telescopes astronomers have developed. Astronomers use telescopes that range from long wave radio up to gammas. If what we saw was more or less the same across the EM spectrum there would be little justification for this plethora of devices, some of which are very expensive.

I don't think that was the question, at least that's not how I interpret it. Obviously things can look dramatically different in different energy bands, but if the emission levels in those more-exotic bands is low then a detector with a flat response would hardly notice.
 
  • #11
Well, one example of how different things could look, if you could see magnetic fields, Jupiter would look something like this.
magneticFiled.jpg


Though I should note they have the wrong moonphase in that image, given the direction of the sun implied by the magnetic field and the moon are almost perpendicular to each other.
 
  • #12
Bd1Dd.png


I basically mean something like this -- going from the real-life, current visible spectrum slice and expanding it to where the bold lines are instead. Most of the matter that we are used to seeing with color, on our planet, would appear greenish, but we'd be able to see everything else, too, outside of the 390 to 750 nm range. I'm wondering what that would look like, or what the night sky would look like. I am just trying to understand what would look different and how.
 

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