The quest to find the darkest place on Earth is a journey into scientific extremes, moving beyond the simple idea of night to explore environments where photons—the fundamental particles of light—are actively blocked or completely absent. Darkness, in this context, is not merely the time between sunset and sunrise, but a measurable phenomenon dictated by the physics of light absorption, scattering, and physical shielding. Exploring these environments, from the deepest trenches to protected underground laboratories, reveals the immense power of natural barriers to create areas of near-absolute blackness.
Defining and Measuring Absolute Darkness
Quantifying darkness requires measuring the presence of light, typically done using the unit of illuminance called the lux (lx). One lux is defined as one lumen of visible light distributed over one square meter of surface area. For comparison, a clear, full moon provides about 0.05 to 0.3 lux, while a moonless night sky, illuminated only by starlight and airglow, registers as low as 0.002 lux.
Absolute darkness, or 0 lux, represents the total absence of visible photons. This state is nearly impossible to achieve in any natural environment on the planet’s surface, as even the faintest starlight can be registered by sensitive instruments. However, deep within certain media, the sun’s radiation is rapidly attenuated through a process called light attenuation. This process involves light being absorbed and scattered as it travels through a medium like air, water, or rock, determining how quickly true darkness is achieved.
The Deep Ocean (Abyssal Zones)
The deep ocean represents a vast, naturally occurring zone of near-absolute darkness due to water’s powerful ability to absorb light. The ocean is divided into zones based on light penetration, starting with the euphotic zone where photosynthesis occurs. Below this is the dysphotic, or twilight, zone, extending from about 200 meters down to 1,000 meters, where light penetration is minimal.
As light travels deeper, its energy is stripped away because water molecules absorb different wavelengths at varying rates. Red light, the longest visible wavelength, is absorbed almost entirely within the first 10 meters. This absorption is why objects appear blue or green at moderate depths, and even blue light becomes so diffused that less than one percent of surface light reaches 100 meters.
Below 1,000 meters lies the aphotic zone, which includes the bathypelagic, abyssal, and hadal zones. In these areas, no sunlight penetrates at all, resulting in total and permanent darkness. The only light sources are the brief, blue-green flashes of bioluminescence produced by organisms living in this high-pressure environment, which is a form of chemical energy conversion, not residual sunlight.
Subterranean Extremes (Caves and Mines)
Extreme darkness is also achieved through geological shielding deep within the Earth’s crust, rather than light absorption. Subterranean environments like deep caves, lava tubes, and abandoned mines create a near-perfect barrier against all forms of external radiation, including sunlight. The sheer density and thickness of rock above an underground chamber physically block solar radiation from reaching the interior.
This profound geological shielding is sought after by scientists for highly sensitive experiments. For example, facilities like the Sanford Underground Research Facility (SURF) in South Dakota are located nearly a mile underground in a former gold mine. The overlying rock mass reduces the bombardment of cosmic rays—high-energy particles that generate unwanted light signals—by a factor of a billion.
The darkness in these subterranean labs is distinct from the ocean’s darkness because it results from physical blockage, not the scattering and absorption process that occurs in water. These deep rock chambers shield against diffuse, high-energy particles that constantly rain down on the planet’s surface. This environment is essential for research, such as the hunt for dark matter, which requires an ultra-low background radiation setting to detect minuscule signals.
Astronomical Darkness (Darkest Skies)
A different interpretation of the “darkest place” refers to the darkest skies on Earth, measuring the absence of artificial light pollution. This darkness is quantified using metrics like the nine-level Bortle Dark-Sky Scale, where a Class 1 rating signifies the most pristine, naturally dark skies. These locations are characterized by a skyglow so faint that the Milky Way appears highly structured and can cast shadows on the ground.
The darkest skies are found in remote, high-altitude deserts or isolated regions far from urban centers, such as designated International Dark Sky Reserves. At these sites, the limiting magnitude—the faintest star visible to the naked eye—is maximized due to the lack of light scattering from city lights. This darkness is dependent on atmospheric conditions and human impact, contrasting with the deep ocean and subterranean zones, where darkness is governed by natural physics.
While the deep ocean and deep mines represent environments of near-total photon absence, the darkest skies signify the closest approximation to natural celestial darkness on the planet’s surface. This difference highlights the two main contributors to darkness on Earth: natural media that block all light, and human influence that pollutes the natural night.