On this day in physics: 01 March 1966 – first spacecraft crash-lands on Venus, 02 March 1972, the spacecraft Pioneer II was launched which made close passes near Jupiter and Neptune before saying good bye to our lovely solar system. It is now SIX BILLION miles away from us. 03 March 1847, we say Happy Birthday to Alexander Graham Bell, the inventor of the telephone! It is also the birthday of Georg Cantor, the founder of modern set theory, and the first person to define different levels of infinity, the first two being countably infinite and uncountably infinite. Without much surprise, mathematics this intense did wind up driving him insane, and his work was repeatably marred with bouts of insanity. 04 March 1976, we salute the passing of Walter Schottky, the man for whom the Schottky effect is named. The Schottky effect (maybe more on this one day). 05 March 1616- The theory set forth by Copernicus that the Earth orbits the Sun is declared to be false doctrine by Bishop of Albano. 06 March 1913- Niels Bohr wrote the first of three papers regarding his theory of atomic structure. 07 March 1979- Photos from the Voyager spacecraft were analyzed and the ring around Jupiter was discovered. By contrast, the rings of Saturn had been known since 1610. [Source]
Word of the Day- The base units are very important. Think of the unit of force, the Newton. The Newton can be simplified to be kilogram per meter per second squared. So, many units like this are called "derived units". There is a limit to this. In 1875, the Systemme Internacionale met in france and agreed that for the world, there are 7 base units, and went on to determine a standard for each of these. Now most of these units are for human-sized sales, since we are human beings and those tend to be the sizes of items we work with. However, the thing to walk away from in this is that there are really only 7 items which are unique in terms of weights and measures, from which everything else can be explained. So, for this 7 day lapse, I offer you the 7 base units.
The first of these fundamental measurable quantities is of course length. Length determines the distance between objects, or the distance of an object. As we've learned from relativity, this measurement can vary depending on your speed, however in our world we can assume that that speed is roughly constant. The standard unit of length is the meter.
The second measurable quantity, and probably the one most people measure the most is mass. The standard unit of mass is the kilogram, the ONLY standard unit which uses a power of ten prefix (kilo). A kilogram is defined to be the weight of one litre of water, and a litre is of course one thousanth of a cubic meter, the meter being our aforementioned first base unit.
The third measurable quantity is time. We all know what time is, or at least we think we do. It's a very bizarre feature of our universe, and there is nothing which behaves quite like it. It's the only dimension which seems to only move in one direction, constantly pressing us forwards. It puts the order to all the events in our lives, and allows us to traverse space incrementally, as time moves on. The base unit is a second, which is currently defined to be *roughly* nine billion oscillations of light emitted from a Cesium Atom.
The fourth measurable quantity is electric current. As electrons move, they generate a magnetic field, and also an electric field. The motion of electrons is what produces current. Current also produces voltage, and the two are directly relatable with the resistance of the conductor being the multiplier between them. The base unit of electric current is the Ampere.
The fifth measurable quantity is temperature. We check the temperature all the time. Temperature is the amount of energy an object or space contains. Depending on where you are in the world, you probably use Fahrenheit or Celsius, but for calculations, we use the Kelvin. It uses the same gradation as the Celsius scale, i.e. 1K = 1 degree Celsius, but the difference is that 0K is what is known as ABSOLUTE ZERO, absolutely no energy. 0 Celsius is the freezing point of water.
The sixth measurable quantity is the amount of a substance. Not to be confused with mass, this is the count of how many particles there are. The base unit of amount is the mol, or 6.022e23 atoms. One mol of gold, would be much heavier, or have much more mass than one mole of hydrogen, which is significantly lighter. How much there is is a fundamentally measurable quantity.
The seventh and final measurable quantity: luminous intensity, think of the sun shining on your face at high noon versus at sunset. The light intensity is less, and it's possible to think about it as the amount of photons per unit area, the unit of which is candela. The standard candle emits roughly 1 candela of luminous intensity. Candela actually means candle in latin.
So there you go guys, seven words of the day in a single episode. Length, Mass, Time, Current, Temperature, Amount of Substance, and Luminous Intensity. Allegedly, from this, the rest will flow.
Quote of the Day: “How wonderful that we have met with a paradox. Now we have some hope of making progress.”-Niels Bohr
Keywords: Base Units, Meter, Length, Mass, Kilogram, Time, Second, Current, Ampere, Luminous Intensity, Candela, Amount, Mol, Mole, Temperature, Celsius, Kelvin
