Metric System -- One of the Reasons

Metric System -- One of the reasons measurement can be complicated is that there is more than one system in use. Based on the Ancient Roman system, the metric system is based on powers of 10; which is called decimalization. The metric system has been the preferred European and scientific method of measuring sine the 18th century, but is not part of the International System of Units, which is also standardized. Because the metric system is based on powers of 10, units are easier to align. Scientists use the metric system as a way to have a common measurement between countries and over time. Scientists use notation that makes it easier to conceptualize distances much easier, particularly when these distances are large. Mathematical examples include:

If Mike needed a desk that was 5 feet by 4 feet wide, how many inches of trim would he need for the whole desk. If trim is measured in metric units, not inches or feet, additional calculations would need to be made. So the math would be 5 X 4 = 20-foot perimeter for the trim, and there are 12 inches per foot, so 20 X 12 = 240 inches, then converted to metric, would result in 6.096 meters, or roughly 6.1 trim. Since metric is more international in scope, Mike's chances of pricing and finding appropriate materials are greater.

2. In scientific notation, it is easier to use powers (ratio) for very large or very small numbers. For instance, in scientific notation, 420,000 becomes 4.2 X 105, which is much easier to notate when dealing with materials that require numerical notation.

Part 1B - Distances -- Particularly in the sciences that deal with very large or very small distances, some units are measured differently in order to make their meaning much clearer. For example, if we measure the distance from the Earth to the Moon as 240,000 miles, and the distance from the Earth to the Sun as 94,000,000 miles, we can conceptually understand these terms and compare the differences. Even if we make it easier to read and write in scientific notation, we can still see an easy relationship: The distance from the Earth to the Moon is 2.4 X 105, while the distance from the Earth to the Sun is 9.4 X 107. When dealing with astronomical concepts, though, distances increase to trillion or zillions of miles -- too many zeros. In this case, we use light years and astronomical units (AU). AU uses the Earth to Sun ration as 1:1, so Earth to Venus is .72 AU. When distances become even larger, it is more understandable to measure in light years, or the distance it takes a particle of light to travel in a year; roughly 6 trillion miles or 10 trillion kilometers. A better example of the need for alternative notation comes when we think about the nearest star to Sol, Alpha Centuri. We can express this as 4.3 light years, 247,000,000,000 miles or 2.47 X 1011. The terms defined are: 1) Light years = an astronomical unit of measurement that is equal to the distance light travels in a vacuum in one year; or about 6 trillion miles or 10 trillion kilometers., 2) AU = astronomical unit, based on the distance from the Earth to the Sun as 1:1 or 92,955,807.3 miles (9.3 X 107 miles).

Part 2A - Apparent magnitude, or stellar magnitude) is a measure of brightness as seen by someone observing an object from Earth adjusted o the value it would have if there were no atmosphere -- the brighter the object, the lower its magnitude. Absolute magnitude corrects from the observer's perspective and measures an object in intrinsic brightness. The absolute magnitude equals the apparent magnitude as if it were a standard luminosity distance, for astronomers 10 parsecs of 1 AU, depending on the type of object. Absolute magnitude is like he luminosity of an object -- how bright it is irrespective of distance (e.g. The sun has a fixed absolute magnitude regardless of one's location in the universe. Apparent magnitude is the brightness of the object based on one's vantage point -- the closer one gets, the brighter it appears -- it is not more luminous, just closer.

Part 2B -- Hipparchus as a Greek astronomer who viewed he stars and ordered them by his version of brightness (Bright was Magnitude, etc.) down to Magnitude 6, which were stars barely visible to him. With the advent of modern telescopes and advanced math, modern astronomers built upon Hipparchus' methods but understood that his perception did not really correspond to the actual brightness of the object because the human eye tends to make judgments. Modern astronomy uses a scale and ratio of brightness that is more quantitative, or precise, regardless of the observer.

Part 3A -- The Ptolemaic and Copernican models of the universe were based on observation and content knowledge of the time; Ptolemy in the Ancient World, Copernicus in the Renaissance. Ptolemy saw the Earth as the center of the universe, with all other celestial bodies revolving around the Earth. Copernicus challenged this by mathematically proving that the Earth revolved around the Sun, or heliocentrism. This actually becomes much more than a scientific debate in that when the Earth was no longer the center of the Universe then perhaps other notions that humans and their relationship to God needed to be redefined. Both Ptolemy and Copernicus believed in a circling orbit; Copernicus allowed for variable speeds, Ptolemy for a constant or uniform speed.

Part 3B- Tycho Brahe was a Danish astronomer living in the mid-late 16th century (1546-1601). He is best known for a more accurate and comprehensive way of observing the universe, and refuting the theory of the celestial spheres by showing Ptolemy was wrong about believing space was unchanging and flowing around the earth. Tycho's model had the Earth stationary, the Sun going around the Earth, and the planets going around the Sun. Brahe also refuted Aristotle's belief of lack of change in the celestial universe, and through mathematical measurements showed that new stars were born while others died. He was also one of the last "naked eye" astronomers.