The highest freqency EM radiation I have ever heard of are cosmic rays. Can higher freqencies exist? If not, why?
Cosmic rays are a mixture of high-energy particles and EM radiation of various energies. The highest band of EM radiation we have a name for are gamma rays, with wavelengths on the order of 10[sup]-12[/sup] meters. The term is a convenient name for any radiation with wavelengths shorter than x-rays.
From this article.
Ooops. But what about the second part of my question with regard to gamma rays then?
Well, for one thing, the term “cosmic rays” is somewhat misleading. Cosmic rays are highly energetic particles, and are not part of the electromagnetic spectrum. The highest frequency range for EM radiation are gamma rays, which have no upper bound that I am aware of. (I’m sure there must be some theoretical upper bound, though, which I’m sure someone will be able to provide.)
Q.E.D., I don’t think that cosmic rays are defined as including EM radiation anymore.
From this pretty good article:
I’m also curious about what the lower frequency limit is for EM radiation now that I think of it.
The main limiting factor for EM wavelengths is energy. Since the most energetic events we know of include supernovae and the Big Bang itself, which produced gamma rays on the order of 10[sup]-15[/sup] to 10[sup]-16[/sup] meters in wavelength, it’s unlikely any natural process can produce more energetic radiation. Practically speaking, that would be the lowermost boundary for EM radiation.
As an aside, in 1997, astronomers detected the most energetic burst of gamma ray emmisions since the Big Bang itself. To this day, the nature of the explosion that produced this burst is not fully understood.
From this article.
There really isn’t one, AFAIK. In theory, at least, you can have EM wavelengths to any arbritraily-chosen large number of meters.
There are no known theoretical frequency limits in either direction (well, you can’t have negative frequency, but other than that…), but there are limits to both detection capabilities and terminology. I don’t think that anyone’s ever produced or observed photons above (at most) a few hundred GeV (giga electron volts), but if we did, we’d still just call them gamma rays. Similarly, I don’t think that anyone’s ever produced or detected radiation with longer wavelength than a few kilometers, but if we did, it’d just be called radio waves.
There might be an upper limit to the frequencies possible, according to some of the potential Grand Unified Theories, but even they don’t put an absolute lower limit on it. I suppose that you’re limited to wavelengths of a few billion lightyears, or so, by the size of the Universe, but that’s not much of a limit.
I wonder if the Planck Limit would relate to a lower bound on wavelength (and thus an upper bound on frequency)???
The lower limit for anything we have a name for is probably ultra-low frequency (ULF), IIRC. From what I hear, submarines use it (or used to use it) for communication through the north pole. Apparently these low frequencies travel quite well through the ice.
Submarines use ELF (extremely low frequency), along with other, higher frequency radio bands. I’m not aware of the use of ULF. Also, ELF communication is not limited to arctic communication.
Cites:
http://www.fas.org/nuke/guide/usa/c3i/elf.htm
http://www.haarp.alaska.edu/haarp/elf/elf.html
Submarines use ELF (extremely low frequency), along with other, higher frequency radio bands. I’m not aware of the use of ULF. Also, ELF communication is not limited to arctic communication.
Cites:
http://www.fas.org/nuke/guide/usa/c3i/elf.htm
http://www.haarp.alaska.edu/haarp/elf/elf.html
Maybe, but we’re far from sure. That’s the potential upper bound I mentioned in my post.
The highest frequency an electromagnetic wave can have is dictated by the Planck length - yah, read those links. I don’t understand entirely, as photons are supposed to be massless ARG!
The idea is that the most energetic photon is just barely above being so dense (remember, according to Einstein, mass and energy are lovingly mixed; also remember that the energy of a photon increases as its frequency increases) that it would collapse into a singularity. It’s the shortest possible length of anything, and far shorter than any massive object, and a completely useless idea to laymen like me. ARG!
I know this is an old thread but I just read it and It seems to me that nobody really answered the question.
IMHO, nonsense like the confusion over photons being waves or particles or a lack of the ability to reason out such a question comes from over reliance on math as an exploratory tool and the distinct lack of an underlying philosophy to unite our study of the world around us. Math does not exactly describe anything. Reality is unique, because it is in constant motion. Math describes static objects or objects in linear motion, not real motion. Whether you call it Heisenberg or not. Mathematics cannot explore the universe, but as a language it can describe and predict aspects of it. The results of mathematical extrapolation become less accurate the further from an actual measurement they predict so siting math equations as proof of shorter or longer waves seems … less than useful. Especially to the non-mathematician.
The longest possible wave would be limited only by the width of the universe or the cosmos or reality itself. Think about it…
The shortest possible wave would be limited by the granularity of the medium through which the wave is propagated. Probably the square of the diameter of the smallest particle. Since there is no known granularity for space “particles” it’s an unknown value but logic makes it clear that waves shorter than gamma are not only possible but a given. Waves traversing the interior of a proton would, by necessity, be super-gamma waves. However, such waves would have little effect upon the electrons surrounding the atom so would have little or no electromagnetic effect and would therefore be invisible to any of our current detection mechanisms. One might, however, detect their effects. Harmonics (above and below a fundamental resonance), for instance, might prove a useful tool for detecting super-gamma waves. A gamma mixer of sorts might also prove useful as might directing gamma waves at varying right angles and measuring chromatic divergence. Such a detector might even pave the way to the propagation and detection of super-g signals and who knows, they might even propagate faster than EM. They would certainly be more noise-immune than EM, being outside the EM envelope. Such a mechanism would be a real boon to telecommunications industries and a black-midnight-nightmare for the cosmologist.:mad:
I think one category of very long wavelengths, much longer than kilometers, would be from rotating or accelerating astronomical objects that have long lasting electrical or (more likely) magnetic fields. For example, earth has a magnetic field that is not perfectly aligned with its rotational axis and so radiates with a frequency of one cycle per day. No doubt lots of astronomical have magnetic fields that would be detectible at a great distance and rotate at much slower than one cycle per day.
People generate plenty of radiation at 20 or 25 Hz, from electric railroad distribution lines. That would have a wavelength somewhat longer than ten million meters.
Sometimes frequencies of 1 Hz are used in laboratory measurements, including precision resistance measurements (I think) and dynamic mechanical analysis (I know). The electrical conductors in such setups would radiate with a one billion meter wavelength.
You could have a wavelength longer than the size of the universe. Nobody says how many cycles of the radiation have to fit into the universe. A signal can be sinusoidal in nature and last for less than one cycle.
The Planck limit was discussed earlier in the thread. Per the linked article, “The fundamental limit for a photon’s energy is the Planck energy.” This would put an upper bound on the frequency for electromagnetic radiation, and thus, a lower limit on the wavelength.
By definition, any EM radiation with a frequency greater than and wavelength shorter than that of x-rays falls into the gamma range. There’s no defined region for EM radiation with a wavelength “shorter than gamma,” nor is there a defined term for “super-gamma waves.”
It’s absolutely true. Once you take the math out you’re free to say anything at all about reality. It won’t make any sense and it will contradict everything math does tell us about reality, but it’s so much more fun.
Not that anyone else will ever agree with your world, but hey …