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Fog is a visible aerosol consisting of tiny water droplets or ice crystals suspended in the air at or near the Earth's surface. [1] [2] Fog can be considered a type of low-lying cloud usually resembling stratus and is heavily influenced by nearby bodies of water, topography, and wind conditions.
Paranal Observatory nights. [3] The concept of noctcaelador tackles the aesthetic perception of the night sky. [4]Depending on local sky cloud cover, pollution, humidity, and light pollution levels, the stars visible to the unaided naked eye appear as hundreds, thousands or tens of thousands of white pinpoints of light in an otherwise near black sky together with some faint nebulae or clouds ...
Dusk is the end of evening twilight. [13] Dawn is the beginning of morning twilight. The brightness and color of the sky vary greatly over the course of a day, and the primary cause of these properties differs as well. When the Sun is well above the horizon, direct scattering of sunlight (Rayleigh scattering) is the overwhelmingly dominant ...
Earth Day is on April 22 because of college schedules. The date for Earth Day was largely dictated by the schedules of the college students Hayes and Nelson were hoping to attract. April 22 fell ...
The date was chosen to appeal to college students. In part, April 22 was chosen as the date for Earth Day because it fell squarely between spring break and final exams — an important distinction ...
With slight magnification, a green rim on the top of the solar disk may be seen on most clear-day sunsets, although the flash or ray effects require a stronger layering of the atmosphere and a mirage, which serves to magnify the green from a fraction of a second to a couple of seconds. [5]
The reverse may happen in the evening sky after dusk, with Mercury or Venus entering retrograde motion just as it is about to overtake another planet (often Mercury and Venus are both of the planets involved, and when this situation arises they may remain in very close visual proximity for several days or even longer). The quasiconjunction is ...
Examples of star-forming regions are the Orion Nebula, the Rosette Nebula and the Omega Nebula. Feedback from star-formation, in the form of supernova explosions of massive stars, stellar winds or ultraviolet radiation from massive stars, or outflows from low-mass stars may disrupt the cloud, destroying the nebula after several million years.