Transcript Document
Seton Hall Prep Weeks of 09/08 and 09/15 Quote: “Any sufficiently advanced technology is indistinguishable from magic” – Arthur C. Clarke The Scientific Method: -The scientific method is an active process that involves scientists using a series of steps to answer specific questions and/or solve problems -These steps involve: *Collecting data and/or making an observation(s) *Asking a question(s) about that data *Forming a hypothesis *Testing that hypothesis through an experiment(s) *Analyzing the results of an experiment *Drawing conclusions *Forming a new hypothesis if necessary -An observation is any use of the senses to gather information -Data collection occurs when many observations are made of the same phenomena (i.e. recording daily midday temperature or the height of every freshman at SHP) -We then ask a general question about trends in our data (i.e. why are midday temperatures warmer in the summer than in winter?) -We are now ready to form a hypothesis; a possible explanation to our general question. A hypothesis is a specific statement that may explain the trends/patterns we see in our data -A hypothesis must be tested to determine if it is valid. Typically, hypotheses are tested through controlled experiments. Note, a hypothesis may also be tested through further observations *Note, experiments MUST be repeatable -Once our controlled experiment is finished, we must analyze our results to see if they support our hypothesis. In many cases, calculations and organizing numerical data into tables or graphs are involved -We then draw a conclusion from our analysis – do our experimental results support our hypothesis? -If our results do not support our hypothesis, we must from a new hypothesis or redesign our experiment -Let’s consider this process; Observations; *The observable universe is incredibly large with a diameter of 46 billion light years *Planets are extremely common around other stars in the Milky Way Galaxy *Most stars in the Galaxy are long lived red dwarves *Basic organic molecules (the building blocks of life) are found everywhere – in meteorites, interstellar gas clouds, nebulae, and on the surface of Saturn’s largest moon Titan *Carbon, the substance that all life on Earth is based upon, is the 4th most abundant element in the universe Question: -Is there intelligent life elsewhere in the Milky Way Galaxy? *Note, by intelligent, we mean a species that has developed a technological civilization that is similar to or has surpassed our own Hypothesis: If there is intelligent life elsewhere in the Galaxy, then we should be able to detect them through their emission of electromagnetic radiation (i.e. radio) *Can we test this hypothesis? -We have been since the 1960s through SETI; the Search for Extraterrestrial Intelligence -SETI is continually testing this hypothesis by using radio telescopes to listen for artificially created radio signals from deep space Analyzing results: -SETI regularly records huge blocks of radio transmissions from deep space over millions of frequencies and then uses computers to look for artificially created signals Drawing a conclusion: -Inconclusive so far. No artificial signals have been found yet but consider that the Milky Way is very large and we have only been looking for about 45 years (not much time from a cosmic perspective) -So, what occurs after our experimental results support our hypothesis and we have drawn a conclusion? We communicate our results -Communicating the results of an experiment is one of the most important components of the scientific method. In most cases, the communication of results occurs through the publication of a scientific paper -It allows other scientists to review what we have done, check our results, conduct their own experiment (repeatability), and draw their own conclusions which may or may not contradict ours -This entire process is known as peer review -Science is NOT a democracy -Through peer review, the work done by individual scientists is constantly being scrutinized and reexamined by other scientists -In the end, if a conclusion drawn from an experiment holds up, it is considered valid (until new data comes along) -We have seen how the scientific method provides us with answers to questions about natural phenomena -Those answers are never final -The process of peer review ensures that our conclusions are always being challenged (when new data comes along) -The activity (forming hypotheses and carrying out experiments) of many scientists in a particular field results in the establishment of scientific laws -A scientific law is a summary of many experimental results and observations. A scientific law is a law of nature; a generalization that will tell us what will happen in a particular circumstance -Well known scientific laws include; Isaac Newton’s Laws of Motion; these laws describe the motion of bodies and the forces that act upon them The Second Law of Thermodynamics; this law tells us that in any closed system, the amount of entropy (disorder) always increases (have you ever seen a broken glass reassemble itself ?) Kepler’s Laws of Planetary Motion; these laws describe the motion of planets around the Sun -Scientific laws predict what things will happen, not why they happen -We can now define a scientific theory. A scientific theory is a unifying explanation for a broad range of hypotheses and observations that have been supported by testing -Scientific theories are repeatedly confirmed through observation and experimentation -A scientific theory explains why a scientific law occurs -Scientific theories have predictive power -When new data is acquired, a scientific theory may be subject to revision (or may even be thrown out) -A scientific theory is NOT an educated guess or opinion. It is the end result of the scientific method being carried out by countless scientists over many years -Well known scientific theories include; The Theory of Evolution; this theory describes how the inherited characteristics of a biological population change over time. It is supported by confirmed hypotheses in taxonomy, molecular biology, genetics, and paleontology Quantum Theory; This theory describes the motion and behavior of atomic and subatomic particles (i.e. photons and electrons) Einstein’s Theory of General Relativity; this theory describes why we experience gravity; because any object with mass ‘warps’ the fabric of space and time -Summing this up; https://www.youtube.com/watch?v=-M1hxGj5bMg Chapter 1 – Section 3 – Using Models in Science: -In science, a model is a representation of a real-world object or system. Models are helpful in making predictions and observations those systems and may even be used in experiments -Keep in mind, a scientific model is a representation, not the actual object or system under study -Cell diagrams, wind tunnel aircraft, and computer designs/simulations are all examples of scientific models -Like scientific laws and theories, models are subject to revision when new data comes along -The Greek astronomer Ptolemy (90-168 AD) constructed this model of the known Universe. In it, Ptolemy explained the motions he observed in the night sky by placing the planets, stars, and Sun in a series of concentric spheres which revolved around the Earth -Ptolemy’s model lasted for over 1,000 years. Why? Because it made relatively accurate predictions about the motions of the planets and stars -It was ultimately revised (drastically) with the invention of the astronomical telescope (when new data came along) -Cosmologists have used computers to model the large-scale structure of the universe Chapter 1 – Section 4 – Measurement: -The International System of Units (SI); the SI System is an internationally agreed upon system of measurement units used by scientists -This system allows scientists to more easily compare their observations and results -The system is based on the number 10 which makes conversions from one unit to another more convenient -First, some very important prefixes; kilo which stands for 1,000 deci which stands for 1/10 or one tenth centi which stands for 1/100 or one one hundredth milli which stands for 1/1000 or one one thousandth -This is much easier to understand when we consider the base SI unit of length, the meter; 1 kilometer (km) contains 1,000 meters (m) 1 km = 1,000 m 1 meter (m) contains 10 decimeters (dm) 1 m = 10 dm 1 meter (m) contains 100 centimeters (cm) 1 m = 100 cm 1 meter (m) contains 1,000 millimeters (mm) 1 m = 1,000 mm -We are now ready to carry out a conversion. Put simply, a conversion is the mathematical process of translating one SI unit in to another using a conversion factor -A conversion typically takes the form; Units given in x · (Units in y/Equivalent units in x) Note; we are looking for our answer in units of y -For example, suppose we want to figure out how many meters are in 3.7 kilometers – we carry out this conversion in the following way; 3.7 km · (1,000 m/1 km) = 3,700 meters -Let’s try another; How many inches are in 4 meters? We first note that 1 meter is equal to 39.3701 inches and run our conversion as follows; 4 meters · (39.3701 inches/1 meter) = 157.48 inches -And one more; How many meters are in 431 centimeters? 431 cm · (1 m/100 cm) = 4.31 meters -What happens when conversions between metric and English units are not done correctly? You can loose a $190 million spacecraft! -In September, 1999, the Mars Climate Orbiter plunged into the Martian atmosphere and burned up due to a failure to correctly convert between two different types of units Volume, Mass, Temperature, Area, and Density: -Volume: the quantity of a three-dimensional space enclosed by some closed boundary. Put more simply, volume is the amount of space that something occupies -There are several SI units used to measure volume; *The cubic meter (m3) *The cubic centimeter (cm3) *The liter (L) *The milliliter (mL) -For volume, why are our meter units cubed? -For the volume of a cube, we multiply the length of each side (length · width · height); 6 cm · 4 cm · 7 cm = 168 cm3 -We use liter units when we are measuring the volume of a liquid. Typically, a graduated cylinder is used for this type of measurement -Conversion factors between volume units; 1 m3 = 1,000 L 1 cm3 = 1 mL 1 mL = 0.001 L 1 L = 1 dm3 = 0.001 m3 -Mass: the property of a physical body which determines the body’s resistance to being accelerated by a force and the strength of its mutual gravitational attraction with other bodies. Fore our purposes, mass is the amount of matter that something is made of -Note; mass and weight are not the same thing. Weight is the force exerted on an object by gravity -Think about it; while you would have the same mass on the surfaces of Earth and the moon, you would have different weights -The kilogram (kg) is the base SI unit for mass. It works much like the meter (m) in regards to conversions; 1 kilogram (kg) = 1,000 grams (g) 1 gram (g) = 1,000 milligrams (mg) 1 metric ton = 1,000 kilograms (kg) -What units would we use to measure the mass of a person, an apple, an aspirin, a car, and an aircraft carrier? -So, why do objects have mass? The answer is stranger than you think; https://www.youtube.com/watch?v=joTKd5j3mzk -Temperature: Put simply, temperature is the numerical measure of how hot (or cold) something is. More specifically, it is the measure of the average kinetic energy of the particles (molecules/atoms) making up an object or substance -The SI unit for temperature is the kelvin (K). Conversions between kelvins and the more common temperature units of Celsius (°C) and Fahrenheit (°F) are as follows; K = °C + 273.15 °C = (5/9)· (°F – 32) -Ok, let’s take a moment and do some basic algebra -So, why use the kelvin (K) unit? Let’s consider a simple conversion; On average, the surface of the Sun measures ~ 6,000 K. What is this in °F? First, we convert from K to °C; 6,000 K = °C + 273.15 °C = 6,000 K – 273.15 = 5,726.85 °C We then convert from °C to °F; °C = (5/9)· (°F – 32) °F = (9/5) · (°C + 32) (9/5) · (5,726.85 °C + 32) = 10,365.93 °F Derived quantities; -Area: the measure of how much surface an object has -Area is a derived quantity because it is formed from a combination of different measurements (i.e. Area = length · width) -The units for area are called square units; m2, cm2, and km2 -Let’s try an example; The runway used for landing the Space Shuttle in Florida is one of the longest in the world (it actually conforms to the curvature of the Earth). What is the area of the runway if its length is 4,572 meters and its width is 91.4 meters -Density: the volumetric mass density of a substance is its mass per unit volume. Put more simply, density is the amount of matter an object has in a given space -Like area, density is a derived quantity – it is formed from a combination of two different measurements (mass and volume) -We can express density (D) with the following equation; D=m/V -Let’s try an example; Suppose we have an object that occupies a volume of 20 cm3 and has a mass of 75 grams (g). Its density would be; D=m/V D = 75 grams / 20 cm3 = 3.75 g/cm3 -Let’s take a moment to think about density. Consider a cubic centimeter (cm3) of air versus a cm3 of lead – which has the greater density? Why? -What will happen if we decrease the volume a substance occupies? Will its density increase? 75 g / 20 cm3 = 3.75 g/cm3 75g / 5 cm3 = 15 g/cm3 -What if we took an object like our Sun and reduced its volume to just a few miles in diameter? Density of Sun = 1.4 g/cm3 Density of neutron star = 590,000,000,000,000 g/cm3 https://www.youtube.com/watch?v=NC8eDLpRmFg Introduction to Chapter 2 – Section 1: Basic Properties of Matter -Matter: anything that has mass and occupies three-dimensional space (volume) -All objects (i.e. the Sun, atoms, rocks, you) take up space – the amount of space taken up is the object’s volume -Jupiter has a volume of 1.43 · 1015 km3! -Recall that m3 and cm3 are used in measuring the volume of solids while L and mL are used for measuring liquid volume. Can we convert between these units? -Suppose we have 5 cm3 of ice. When it melts, what volume does the water occupy? -How do we measure the volume of a gas? -We measure the volume of a gas by measuring the volume of the container it occupies -Using the calculation from your lab, what is the volume of air in this room? -A standard party balloon has a volume of 4,200 cm3 – so, 4,200 cm3 of helium -Recall, there is a difference between mass and weight. Weight is a measurement of the gravitational force exerted on an object -Gravity: one of the four fundamental forces operating in our universe. For our purposes, gravity is a force of attraction between two objects that occurs as a result of their masses. Because all matter has mass, all matter experiences gravity -Gravity is a very weak force -The gravitational attraction between two objects is dependent upon their masses and distance from one another -Gravity operates according to the inverse square law; the strength of attraction is inversely proportional to the square of the distance. We can express the inverse square law for gravity simply as; Gravitational strength α 1/(distance)2 -What does it all mean? That the gravitational attraction between two objects decreases with their increased distance from one another -You actually weigh a tiny bit less in an airplane at 36,000 feet than on the ground since you are further away from the center of the Earth! -Gravitational strength also depends on the masses of the two objects involved; *The smaller their masses, the weaker the gravitational strength between them *The larger their masses, the stronger the gravitational strength -So, if you were standing on the surface of a planet more massive than Earth, you would weigh much more (and weigh less on a planet with a mass smaller than Earth’s) http://www.exploratorium.edu/ronh/weight/ -Can you ‘escape’ from the gravitational attraction of the Earth or Sun? -In order to do this, objects need to achieve escape velocity; the speed needed to break free from the gravitational attraction of a massive body *Earth escape velocity = 11.2 km/s *Sun escape velocity = 617 km/s -How fast is this in miles per hour? -Recall our scientific definition of mass. Mass is a measure of inertia; the tendency of objects to resist any change in motion (acceleration) -Because of inertia, an object at rest will remain at rest until something causes it to move. Likewise, a moving object continues to move at the same speed and in the same direction unless something acts upon it to change its speed or direction -The larger the mass, the greater the inertia Let’s think about this, a soccer and bowling ball are about the same size – can we kick both and expect the same results?