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Optical disc technology is a topic I never understood. How do the microscopic bumps in the optical disc contain data?

Hi Martin. Thanks for the reply. The problem is that wikipedia later says in a different article that "typical galaxies range from dwarfs with as few as ten million (10^7) stars up to giants with one trillion (10^12) stars, all orbiting a common center of mass". http://en.wikipedia.org/wiki/Galaxy So can a dwarf galaxy contain only 10 million stars or is this number too small?

How many stars do dwarf galaxies have? Also how many stars does an average or regular galaxy have?

If air flows away only in the upper troposphere, why does it leave less mass on the surface? http://www.weatherquestions.com/What_causes_low_pressure.htm

Do you know some books who teach you how to write interpreters?