There is a difference between the time under a solar day and a sidereal day. A geostationary satellite has to remain at the same position as seen from earth so it has to follow time of a sidereal day. If it follows a solar day, its position will change with respect to a stationary viewer on earth.
All cells have a cell membrane. its basically what protects the cells from getting toxins that are sometimes entering your body. without a membrane on all cells, you would get sick a lot!!
Commensalism :)
in case when bacteria and human, both are benifited.
Earth and its atmosphere are continuously altered. Plate tectonics shift the continents, raise mountains and move the ocean floor while processes not fully understood alter the climate. Such constant change has characterized Earth since its beginning some 4 billion years ago.
