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Measuring Ultra-Low Frequencies

The attohertz (aHz) is an extremely small unit of frequency equal to 10⁻¹⁸ hertz, or one cycle per 10¹⁸ seconds (about 31.7 billion years). This unit is used to describe ultra-low frequency phenomena that occur on cosmic or geological timescales, far beyond everyday human experience.

Attohertz frequencies are relevant in cosmology, astrophysics, and geophysics, where they help scientists study processes that evolve over billions of years. For example, gravitational waves generated by massive cosmic events or the oscillations of the Earth’s magnetic field can be characterized by frequencies in the attohertz range. These waves have enormous wavelengths, often spanning millions or billions of kilometres.

Because the attohertz corresponds to such a long period between cycles, it is mostly used in theoretical research rather than practical applications. Understanding phenomena at this scale gives insight into the fundamental workings of the universe, including the slow evolution of cosmic structures, the expansion of space-time, and the early conditions following the Big Bang.

The Fundamental Unit of Frequency

The hertz (Hz) is the standard unit of frequency in the International System of Units (SI), defined as one cycle per second. It measures how often a repeating event occurs each second, making it a fundamental concept in physics, engineering, and many branches of science.

Frequency measured in hertz is essential for understanding waves and oscillations, including sound waves, electromagnetic waves, and mechanical vibrations. For example, in acoustics, the pitch of a sound corresponds directly to its frequency in hertz—middle C on a piano has a frequency of about 261.6 Hz.

In electrical engineering, hertz measures the frequency of alternating current (AC), with common household power typically operating at 50 or 60 Hz depending on the country. Radio and television broadcasting frequencies, as well as wireless communication signals, are also expressed in hertz and its multiples.

Because hertz represents a single cycle per second, it serves as the base unit from which all other frequency units are derived, including kilohertz, megahertz, and gigahertz. Understanding frequency in hertz allows scientists and engineers to design and analyze systems ranging from audio equipment to complex telecommunications networks.