[Europan Ocean (OP)]

Is there or are there any types of electromagnetic energy, from heat to X Ray and inbetween, or beyond, can there be any other type of ray?

I am interested because of very low frequency heat energy and it's healing properties.

[evan_au]

There are a variety of names for different parts of the electromagnetic spectrum: Radio waves, microwaves, infra-red, visible, ultraviolet, X-Rays, Gamma rays, etc. Those working in particular parts of the spectrum subdivide it even further, but they are all transverse electromagnetic waves differing only in their:

• Frequency
  
• Wavelength
  
• Energy per photon
  
• The type of matter with which they interact most strongly (eg ions in solution, electrons or protons)
• Intensity (eg Watts per square meter)

With care, there are various ways you can manipulate these electromagnetic waves:

• focussed or diffuse (affects Intensity)
  
• linear polarisation or circular polarisation
  
• coherent (eg from a laser) or non-coherent
  
• monochromatic (one frequency) or black body (eg from an incandescent lamp)
  
• Modulated (to carry information) or not
  
• quantum entangled (but usually not)

The "healthy warmth" you feel is from the energy delivered by infra red, deep under the skin; it does not necessarily mean that you are getting healthier (but it does mean that you won't get frostbite while under the heat lamp, and perhaps muscle aches might feel better for a while). It's unlikely that any of these ways of manipulating electromagnetic waves would affect how much energy is delivered under your skin.

Optical and ultraviolet light does not penetrate as well as infrared. With really low frequencies (like AM Radio frequencies), the waves go right through you around you without affecting you very much. X-Rays and gamma rays can also pass right through you.

Like any form of energy, exposure to excess electromagnetic energy can cause damage instead of giving you a warm, healthy glow - there are safety guidelines for maximum exposure at different frequencies. In particular, with ultraviolet and higher frequencies, it actually damages DNA and can cause cancer

[alancalverd]

You can also cook yourself with ultrasound (not all radiation is electromagnetic!), microwaves, and the near-field of a Hertzian oscillator. X-rays and gamma rays can of course be therapeutic but a lethal dose will only raise your temperature by about 0.001 degree. LIkewise alpha (helium nuclei) and beta radiation (electrons), to say nothing of the cosmic pions and neutrons that zip through your body every day..

[chiralSPO]

How far does this spectrum extend? I know radio waves can have wavelengths in excess of 1 km, and gamma rays are less than 1 Å. Are there theoretical physical limitations to wavelength (could a photon have wavelength less than a Planck length?)

[alancalverd]

No lower frequency limit. I guess the upper limit in principle is where all the mass in the universe is converted into a single photon. 

[syhprum]

It would be helpful if correspondents could use S.I units instead of obsolete units such as Ångstroms.

[evan_au]

To add to Alan's comment:
There are practical limits to the lowest radio frequencies we can detect. For example, the Sun's magnetic cycle has a wavelength of about 22 light-years.

We can detect and measure this oscillating field because we are relatively close to the Sun, and we can use the Zeeman effect at optical wavelengths to measure the local strength of magnetic fields at the surface of the Sun.

However, there are practical limits to building an antenna that would efficiently pick up transmissions from magnetic oscillations in other stars; to be efficient, an antenna typically should be around half a wavelength in size; if you want it to be directional, it should be at least a wavelength in size in the other direction. This size is less than the spacing of stars in our galactic neighbourhood!

It would be easier to look for cycles in the optical Zeeman effect on other stars than to detect this incredibly low-frequency electromagnetic radiation directly.

[chiralSPO]

1 Å = 1 x 10^–10 m = 100 pm (picometers)

[syhprum]

I know full well what a Ångstrom is but it is an odd unit S.I units go in step 10^3 or 10^-3 to define it in terms of pico units introduces an odd factor of 100, why not talk about Pico or Nano meters

[alancalverd]

Because SI is OK for the sort of people who sit on committees and devise arbitrary rules that kill patients (try deciphering the symbols for milli, mega and micro from the average doctor's handwitten prescription). In real life, proper scientists prefer to have one digit before the decimal point (that's why it's called "scientific notation") so atomic radii are measured in angstroms.

No machine designed in SI units has ever landed a man on the moon, or explored Mars. But can you buy a Letter B drill so you can put a Whitworth thread on a 3/8ths pipe? Another case of the malign influence of Europe. Jumo 210 versus Rolls-Royce Merlin? No contest. Now warm beer, there's another thing.....