After measuring the speed of sound u several times, a student concludes that the standard deviation of u of her measurements is sigma_u = 10 m/s. if all uncertainties were random, she could get any desired precision by making enough number of measurement and averaging. how many measurements are needed to have the final uncertainty of the speed of sound plusminus 3 m/s ? how many measurements are needed to have the final uncertainty of the speed of sound plusminus 0.3 m/s ?

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

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