When astronomers observe distant galaxies, they can tell that most of them are moving away from one another. In addition, the more distant the galaxies, the more rapidly they are likely to be moving away from each other. Can you devise a hypothesis to explain these observations?

Solution 36E: There are two types of number in scientific work. (i) Exact number - exactly the values are known when it is measured. The values which are obtained from any measurement is completely certain value. The values have no uncertainty. (ii) Inexact number- These number have some sort of uncertainty in their values. The measured values are uncertain. a) the mass of a 32-oz can of coffee, It is an inexact number. This is because, the mass of a 32 oz can of coffee can be measured in different equipment and it will always give a different value. This measurement is associated with equipment error. (b) the number of students in your chemistry class It is always an exact number. The number of students in my chemistry class will always be same at least for a year and the counting of the students always give the exact number. (c) the temperature of the surface of the Sun, It is always an inexact number. This is because, the the temperature of the surface of the Sun is calculated based on the mathematical formula which based on assumption. So assumption could not give you the exactly same value. Therefore, the measured values would have the possibility of uncertainty. (d) the mass of a postage stamp It is s an inexact number. Different people can measure the mass of a postage stamp by using different weighing balance. Therefore, there would be always have a possibility to get different values for the mass of a postage stamp due to the instrumental error. (e) the number of milliliters in a cubic meter of water, 6 It is always an exact number. This is because 1 cubic meter of water = 10 mL. The measured values are certain. (f) the average height of NBA basketball players. It is s an inexact number. Different NBA basketball players have different height. Their measured average height will be different.