If a lightning strike is a sufficient distance from the observer, sound from the strike will not be heard. These silent bolts are called heat lightning. Lightning bolts produce thunder, but the thunder sound does not travel all the way to the observer if the observer is too far away. The movement of sound in the atmosphere depends on the atmospheric properties of the air such as temperature and density.
Collagen vascular diseases are autoimmune diseases that affect connective tissues, and occur when the bodyâs immune system attacks its own tissues and organs. Lupus is often characterized by a facial rash on both cheeks. Lupus patients may experience fatigue, joint pain, skin lesions and shortness of breath.
Common symptoms of Crohn's disease include abdominal pain, diarrhoea, and weight loss. Less common symptoms include poor appetite, fever, night sweats, rectal pain, and rectal bleeding. The symptoms of Crohn's disease are dependent on the location, the extent, and the severity of the inflammation.