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A halo (from Ancient Greek ἅλως (hálōs) 'threshing floor, disk') [1] is an optical phenomenon produced by light (typically from the Sun or Moon) interacting with ice crystals suspended in the atmosphere. Halos can have many forms, ranging from colored or white rings to arcs and spots in the sky.
The spectrum does not contain all the colors that the human visual system can distinguish. Unsaturated colors such as pink, or purple variations like magenta, for example, are absent because they can only be made from a mix of multiple wavelengths. Colors containing only one wavelength are also called pure colors or spectral colors. [8] [9]
This effect is more pronounced closer to the poles, where the Sun rises at the vernal equinox and sets at the autumn equinox, with a long period of twilight, lasting for a few weeks. [citation needed] The polar circle (at 66°33′50.3″ north or south) is defined as the lowest latitude at which the Sun does not set at the summer solstice.
We also see the Rayleigh effect at play in: - Sunsets where the sky is red. Light has to pass through a larger part of the atmosphere when the sun is lower on the horizon.
On Mars, the setting Sun appears about two-thirds the size it does from Earth, [21] due to the greater distance between Mars and the Sun. The colors are typically hues of blue, but some Martian sunsets last significantly longer and appear far redder than is typical on Earth. [22] The colors of the Martian sunset differ from those on Earth.
The four pigments in a bird's cone cells (in this example, estrildid finches) extend the range of color vision into the ultraviolet. [1]Tetrachromacy (from Greek tetra, meaning "four" and chroma, meaning "color") is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye.
Fig. 1. HSL (a–d) and HSV (e–h). Above (a, e): cut-away 3D models of each. Below: two-dimensional plots showing two of a model's three parameters at once, holding the other constant: cylindrical shells (b, f) of constant saturation, in this case the outside surface of each cylinder; horizontal cross-sections (c, g) of constant HSL lightness or HSV value, in this case the slices halfway ...
The northernmost town in America is about to experience several weeks of darkness. After getting 30 minutes of daylight, the town of Utqiaġvik, Alaska – formerly known as Barrow – saw its ...