Negative ions are invisible, odorless, tasteless molecules that we inhale in abundance in environments like mountains, waterfalls, and beaches. They appear in nature when air molecules split due to sunlight, radiation, and moving air and water. Once in our bloodstream, negative ions are believed to produce biochemical reactions that increase levels of serotonin (the mood chemical), helping to alleviate depression, relieve stress, and boost daytime energy levels.
Fog is a compact cloud of minuscule water droplets suspended in the atmosphere near the earth’s surface. If visibility is restricted to 1km or less, it is considered ‘fog’. If visibility is greater than 1km, it is called ‘mist’. Atmospheric pollutants can intensify fog and turn it into ‘smog’, a portmanteau of the words ‘smoke’ and ‘fog’.
Snow is atmospheric water vapor frozen into ice crystals. Although these crystals/snowflakes typically display a six-sided symmetrical shape, each one is unique in structure. You might expect snow to appear transparent since it is made out of water. However, snow has so many light-reflecting surfaces (myriad snowflakes) that it splits the light into all of its colors (frequencies), which then blend together to give snow its pristine white color.
An altimeter used in conjunction with a topographic map can help verify location and aid navigation. A barometric altimeter can be more reliable and more accurate than a GPS receiver for measuring altitude. GPS altimeters may have difficulty in finding a signal, e.g. in a deep canyon or beside a steep cliff, and may give inaccurate measurements if available satellites are near the horizon and line of sight is blocked.