Chances are the lake closest to you is a freshwater lake. But some lakes are extremely salty. These are called saline lakes. Although freshwater lakes often have minor amounts of dissolved salts in them (less than 1-3 g/L), saline lakes have more than this (between 3 and 300g/L).
Astronomical Unit (A.U.). An astronomical unit (A.U.) is the average distance between the Earth and the Sun, which is about 93 million miles or 150 million kilometers.Astronomical units are usually used to measure distances within our solar system.ne kiloparsec (kpc), is one thousand parsecs. One megaparsec (Mpc) is one million parsecs. SUMMARY 1 Astronomical Unit (A.U.) is the average distance between the Sun and the Earth. 1 A.U. = 93 million miles = 150 million kilometers 1 light-year (ly) is the distance that light travels in one year in a vacuum.
The first step in measuring the distance between the Earth and the Sun is to measure the distance between Earth and another planet in terms of the distance between Earth and the Sun. So, let us assume that the distance between Earth and the Sun is a.Now, let us consider the orbit of Venus.To first approximation, the orbits of Earth and Venus are perfect circles around the Sun. Take a look at the diagram below (not to scale).nyway, the relevant numbers are: Earth-Sun distance, d = roughly 150 million km (defined as 1 Astronomical Unit). Radius of the Sun, R sun = roughly 700,000 km. Orbital speed of Earth, v = roughly 30 km/s. References: 1  Great Moments in the History of Solar Physics 1.