ELF (Extremely Low Frequency)

ELF (Extremely Low Frequency) refers to radio waves with frequencies between 3 and 30 Hz, which are very low compared to typical radio signals. These signals can penetrate water, soil, and the Earth itself, making them useful for communicating with submarines and monitoring Earth's natural phenomena like earthquakes and lightning. Because ELF waves travel long distances with little energy loss, they are ideal for transmitting information across vast areas. However, generating and detecting ELF signals requires large, specialized equipment, which is why ELF communication is primarily used for specific scientific and military purposes.