The Sun is about 30,000 lightyears from the center of the Milky Way and orbits around that center in about 200 million years, with an average speed of about 230 km/s or 800,000 km/h. The Sun has completed about 23 of those orbits so far. Our Milky Way is a spiral galaxy with a diameter of about 100,000 lightyears and seems to contain at least four spiral arms. The Sun lies between the Sagittarius-Carina arm and the Perseus arm. Interestingly enough, the Milky Way also moves relative to the center of gravity of the Local Group of galaxies at a speed of about 40 km/s (144,000 km/h).
Vertical Structure of the Atmosphere Troposphere The Troposphere starts at the ground or sea and reaches up to 10 - 12 km height. It is the troposphere where most weather phenomena like cloud formation take place. Physically it is characterized by a continuous decrease of temperature with increasing height. The uppor boundary of the troposphere is called tropopause. The height of the tropopause is very dependent on geographical latitude and season. Troposphere has it's maxmum height in tropical regions. At the polar regions, the tropopause is located at about 8 km height. The troposphere contains about 80 % of the mass of the atmosphere and also contains almost all of water of the atmosphere. In it's lowest layer of about 1 to 2.5 km, the planetray boundary layer (PBL), the influence of Earth's surface causes heavy variances of meteorologic parameters like temprature, wind and humidy. In the higher regions of the tropopause, temperature is about -60 °C. At this he