Electromagnetic waves consist of two waves oscillating perpendicular to one another. One of the waves is an oscillating magnetic field; the other is an oscillating electric field. These waves interact with matter, producing different results.
The electromagnetic spectrum is a continuous range of wavelengths. This spectrum includes visible light, X-rays and radio waves. The types of radiation that occur in different parts of the spectrum have different uses and dangers, depending on their wavelength and frequency.
- Radio waves have the lowest frequencies and longest wavelengths, while gamma rays have the highest frequencies and shortest wavelengths.
All of these waves travel at the same speed within the vacuum of space (the speed of light – about 300,000 km per second).
The electromagnetic spectrum shows electromagnetic waves with frequencies ranging from below one hertz to above 1025 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus. This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names and have a variety of practical applications.
- Radio waves. The interaction of radio waves with matter generates tiny electrical charges. Common uses include communications and television signals
- Microwaves. The interaction of microwaves with non-conductive matter produces heat. Conductors will strongly absorb microwaves, causing electric currents and heating the material. Common uses include food preparation and cellphone signals.
- Infrared. Common uses include vision enhancement devices and optical fiber systems.
- Visible light – natural human vision.
- Ultraviolet. Common uses include "convenience" sensors, such bioscans and detecting forged currency.
- X-rays. Common uses include medical imaging of internal structures.
- Gamma rays. Common uses include killing cancerous cells.
A detailed understanding of the electromagnetic spectrum begins with the development of precise scientific instruments.
- Modern sensor systems are used to detect and analyze portions of the EM spectrum.
Humans form the baseline for visual perception of the electromagnetic spectrum: it is perceived as colors.
Different organisms, with different senses, can perceive different regions of the spectrum compared to humans, also seeing these different frequencies of energy as unique colors. This is extremely common - even Terran creatures, native to the human homeworld, can see further into the infrared or ultraviolet than humans. Other species of creatures and sophonts, originating on worlds orbiting different types of stars and having evolved in radically different environments and conditions, may have the ability to view more extreme regions of the spectrum.
Except for a few gifted sophont species, most NILs lack the bodily ability to sense more than a very limited part of the electromagnetic spectrum. As technology develops, particularly in relation to the construction of electronics in the TL:7-9 technological epoch, sophonts create sophisticated devices to sense that which their bodies cannot and translate that data into information that they can.