Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

After seeing this image:

http://mynasadata.larc.nasa.gov/images/EM_Spectrum3-new.jpg

And reading this:

"The long wavelength limit is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length, although in principle the spectrum is infinite and continuous."

The question is, how did the EMS evolve? Was it weak at first, i.e. at Planck time, which allowed certain reactions to modify, shape or add properties to it?

What really defined the position and order of everything that is the EMS? E.g. colors. What defined or added something as colors to be inserted in that specific range of 400nm to 700nm.

Hope this is not to philosophical and thanks in advance.

share|improve this question

closed as not a real question by Noldorin, mbq, Marek, David Z, ptomato Dec 2 '10 at 20:41

It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center.If this question can be reworded to fit the rules in the help center, please edit the question.

3  
The human eye defined EM wave of wavelength 400–700nm as having colors. –  KennyTM Dec 2 '10 at 19:30

2 Answers 2

I think saying that the EMS evolved isn't really an accurate description. The EMS simply is. The upper limit (the size of the universe) is because a wave can't be bigger than the system that contains it.

Nothing defines the position or order. It's simply a number line, from small to large. There's nothing inherently special to the visible range. It's simply the range that humans evolved to perceive. We might just have easily evolved to perceive the infrared spectrum.

You're putting too much weight on what it's called. All of that is just human-centric thinking. A wavelength of 400700nm doesn't care that it looks red.

share|improve this answer

The EMS is a reflection of the properties and laws of the universe. The light that you see starts from the emission of a fusion reaction, filtered by molecules in the atmosphere which themselves are selected by the construction and mass of the planet.

So just after the big bang, the light would have been mostly very high energy, and short wavelength, as the types of matter that produce longer wavelength EM (molecules, polymers) didn't exist.

As the universe expanded and matter formed, fusion produced heavier atoms and enabled the larger molecules, and the length scales at work allowed resonances at longer wavelengths.

Remember, though, that light is emitted in a continuous spectrum as black body radiation, from all objects with a temperature above zero. So once anything could vibrate and thus have a temperature, it would emit such a spectrum.

Largely, the universe began at the very short, hot end of the spectrum, and will eventually die at the long, cold end, unless some sort of crunch reverses it. Even the beyond-gamma radiation of the big bang itself is now microwave background radiation.

So goes the current theory, anyway.

share|improve this answer
    
I love the last sentence. Especially the word current. Surely, tomorrow all will be different :-) –  Marek Dec 2 '10 at 20:13

Not the answer you're looking for? Browse other questions tagged or ask your own question.