Geodesy and the Earths Size and Shape

Geodesy and the Earths Size and Shape Earth, with an average distance of 92,955,820 miles (149,597,890 km) from the sun, is the third planet and one of the most unique planets in the solar system. It formed around 4.5 to 4.6 billion years ago and is the only planet known to sustain life. This is because of factors like its atmospheric composition and physical properties such as the presence of water over 70.8% of the planet allow life to thrive. Earth is also unique however because it is the largest of the terrestrial planets (one that have a thin layer of rocks on the surface as opposed to those that are mostly made up of gases like Jupiter or Saturn) based on its mass, density, and diameter. Earth is also the fifth largest planet in the entire solar system. Earths Size As the largest of the terrestrial planets, Earth has an estimated mass of 5.9736 Ãâ€" 1024 kg. Its volume is also the largest of these planets at 108.321 Ãâ€" 1010km3. In addition, Earth is the densest of the terrestrial planets as it is made up of a crust, mantle, and core. The Earths crust is the thinnest of these layers while the mantle comprises 84% of Earths volume and extends 1,800 miles (2,900 km) below the surface. What makes Earth the densest of these planets, however, is its core. It is the only terrestrial planet with a liquid outer core that surrounds a solid, dense inner core. Earths average density is 5515 Ãâ€" 10 kg/m3. Mars, the smallest of the terrestrial planets by density, is only around 70% as dense as Earth. Earth is classified as the largest of the terrestrial planets based on its circumference and diameter as well. At the equator, Earths circumference is 24,901.55 miles (40,075.16 km). It is slightly smaller between the North and South poles at 24,859.82 miles (40,008 km). Earths diameter at the poles is 7,899.80 miles (12,713.5 km) while it is 7,926.28 miles (12,756.1 km) at the equator. For comparison, the largest planet in Earths solar system, Jupiter, has a diameter of 88,846 miles (142,984 km). Earths Shape Earths circumference and diameter differ because its shape is classified as an oblate spheroid or ellipsoid, instead of a true sphere. This means that instead of being of equal circumference in all areas, the poles are squished, resulting in a bulge at the equator, and thus a larger circumference and diameter there. The equatorial bulge at Earths equator is measured at 26.5 miles (42.72 km) and is caused by the planets rotation and gravity. Gravity itself causes planets and other celestial bodies to contract and form a sphere. This is because it pulls all the mass of an object as close to the center of gravity (the Earths core in this case) as possible. Because Earth rotates, this sphere is distorted by the centrifugal force. This is the force that causes objects to move outward away from the center of gravity. Therefore, as the Earth rotates, centrifugal force is greatest at the equator so it causes a slight outward bulge there, giving that region a larger circumference and diameter. Local topography also plays a role in the Earths shape, but on a global scale, its role is very small. The largest differences in local topography across the globe are Mount Everest, the highest point above sea level at 29,035 ft (8,850 m), and the Mariana Trench, the lowest point below sea level at 35,840 ft (10,924 m). This difference is only a matter of about 12 miles (19 km), which is quite minor overall. If the equatorial bulge is considered, the worlds highest point and the place that is farthest from the Earths center is the peak of the volcano Chimborazo in Ecuador as it is the highest peak that is nearest the equator. Its elevation is 20,561 ft (6,267 m). Geodesy To ensure that the Earths size and shape are studied accurately, geodesy, a branch of science responsible for measuring the Earths size and shape with surveys and mathematical calculations is used. Throughout history, geodesy was a significant branch of science as early scientists and philosophers attempted to determine the Earths shape. Aristotle is the first person credited with trying to calculate Earths size and was, therefore, an early geodesist. The Greek philosopher Eratosthenes followed and was able to estimate the Earths circumference at 25,000 miles, only slightly higher than todays accepted measurement. In order to study the Earth and use geodesy today, researchers often refer to the ellipsoid, geoid, and datums. An ellipsoid in this field is a theoretical mathematical model that shows a smooth, simplistic representation of the Earths surface. It is used to measure distances on the surface without having to account for things like elevation changes and landforms. To account for the reality of the Earths surface, geodesists use the geoid which is a shape that is constructed using the global mean sea level and as a result takes elevation changes into account. The basis of all geodetic work today though is the datum. These are sets of data that act as reference points for global surveying work. In geodesy, there are two main datums used for transportation and navigation in the U.S. and they make up a portion of the National Spatial Reference System. Today, technology like satellites and global positioning systems (GPS) allow geodesists and other scientists to make extremely accurate measurements of the Earths surface. In fact, it is so accurate, geodesy can allow for worldwide navigation but it also allows researchers to measure small changes in the Earths surface down to the centimeter level to obtain the most accurate measurements of the Earths size and shape.

Average AP Scores for Every AP Exam

Average AP Scores for Every AP Exam SAT / ACT Prep Online Guides and Tips Taking an AP class this year? You might be wondering about average AP scores or what good AP scores are for certain classes. Or if you are thinking about taking AP exams in the future, you might want to know which exams have the highest passing rates. In this post, we will break down the average score for each AP test, as well as the average passing rate. We will also show you how to interpret this info and how to use it to make decisions about your schedule. Average AP Score by Test Instead of giving you an overall average score for all AP tests, we will show you the average score for every AP exam. We break it down by test because every AP test is different. It’s important to know the average score for whichever test you are taking or thinking about taking. We will also explore how you can use this info- and learn why the exams with the highest passing rates are not the easiest! But first, the data. The table contains the national average scores for each AP exam from 2018. Remember that AP exams are scored from 1 to 5, with 3 and higher considered passing rates. We have sorted the exams from highest average scoreto lowest. Take a look: AP Test Average Score Chinese Language 4.31 Calculus BC 3.74 Japanese Language 3.70 Spanish Language 3.69 Studio Art Drawing 3.65 Physics C EM 3.60 Physics C Mechanics 3.55 Studio Art 2-D Design 3.48 Spanish Language (Standard) 3.45 French Language 3.32 German Language 3.31 Economics - Micro 3.21 Computer Science A 3.18 Music Theory 3.18 Research 3.17 French Language (Standard) 3.16 Seminar 3.15 Italian Language 3.14 Psychology 3.14 Gov. and Politics - Comparative 3.12 Computer Science Principles 3. Studio Art 3-D Design 3. Chinese Language (Standard) 3.06 Spanish Literature 3.06 Calculus AB 3.05 Art History 3.04 Physics 2 2.97 German Language (Standard) 2.96 Economics - Macro 2.96 Latin 2.94 Japanese Language (Standard) 2.89 European History 2.89 Italian Language (Standard) 2.88 Statistics 2.88 Biology 2.87 English Language 2.83 Chemistry 2.80 World History 2.78 Human Geography 2.72 Gov. and Politics - US 2.70 United States History 2.66 Environmental Science 2.63 English Literature 2.57 Physics 1 2.36 Via College Board. Check out the link for a complete distribution of scores for each AP exam. Want to get a perfect 5 on your AP exam and an A in class? We can help. PrepScholar Tutors is the world's best tutoring service. We combine world-class expert tutors with our proprietary teaching techniques. Our students have gotten A's on thousands of classes, perfect 5's on AP tests, and ludicrously high SAT Subject Test scores. Whether you need help with science, math, English, social science, or more, we've got you covered. Get better grades today with PrepScholar Tutors. One very important fact to note is that high average scores don't correspond to the easiest exams! Chinese, Calculus BC, Japanese, and Spanish Language are the AP tests with the highest average scores, but they are all known to be quite difficult. Also note that native speakers, or students with experience living abroad, tend to take the AP language exams, which inflates their average scores (for the average of those who learned in a classroom, check the "Standard" score). Furthermore, some of the tests with the lowest averages are often regarded as some the easiest APs- Human Geography, Environmental Science, and US Government. So why are their passing rates so low? This is because freshmen and sophomores might take these as their first-ever AP classes. Even though the content is easier than, say, Calculus, all AP exams are tough and could be hard for a younger student to do well on. It’s also possible that students simply don’t study enough for the â€Å"easier† exams because they underestimate them. All AP tests are difficult, even if some are easier than others. To sum up, the average score can say more about the students taking the exam than the exam itself. Don’t sign up for BC Calculus just because the average score is super high. And by the same token, don’t avoid AP Environmental Science because the average score is relatively low. Focus on your own strengths and interests when signing up for AP classes! What's a Good AP Score? Beyond the basic averages, it’s helpful to have some context about what a "good" AP score is. A score of 3 or higher is generally considered good, because that means you passed the exam! A 4 is considered very good, and a 5 is especially impressive since it is the highest score. Also keep in mind that every college sets its own policy about AP credit. Some schools only give credit for scores of 4 or 5. Check the AP credit database to find out the AP credit policy for schools you're interested in. But with that in mind, let’s look at which 2019 AP exams have the highest passing rates- a.k.a. rates of scores over 3. We also note the percentage of students who get a 5, the highest score. Exam Name Passing Rate (3+) 5 Rate Studio Art: Drawing 91.1% 20.8% Spanish Language and Culture 89% 24.9% Chinese Language and Culture 88.3% 57.2% Studio Art: 2-D Design 86.4% 21% Calculus BC 81.5% 43.2% Physics C: Electricity Magnetism 81.1% 35.9% Seminar 80.7% 6.8% French Language and Culture 76.7% 15.5% Research 76.2% 10.8% Japanese Language and Culture 75% 38.2% Computer Science Principles 72.7% 13.6% Spanish Literature 71.9% 9.1% Physics C: Mechanics 71.1% 34.6% German Language and Culture 70.5% 18.4% Studio Art: 3-D Design 70.1% 10.1% Computer Science A 69.9% 27% Microeconomics 68.4% 22.2% Gov. and Politics - Comparative 66.2% 22.2% Biology 64.6% 7.1% Italian Language and Culture 64.6% .8% Psychology 64.4% 20.2% Art History 63.9% 12% Physics 2 63.5% 12.6% Music Theory 63.4% 20.9% Latin 63.1% 13.1% Statistics 59.2% 14.5% European History 58.4% .7% Calculus AB 58.3% 18.9% Macroeconomics 57.9% 17.6% World History 56% 8.7% Gov. and Politics - United States 55.2% 12.9% English Language and Composition 55.1% 10.1% Chemistry 54.6% 10.7% United States History 54.3% 12.1% English Literature and Composition 50.1% 6.2% Environmental Science 49.6% 9.5% Human Geography 49.1% 10.7% Physics 1 44.6% 6.2% Source: College Board. For language rates, "Total" includes all students, while "Standard" includes only those students who didn't indicate they speak this language at home or spent more than four weeks studying it abroad. Again, note that some of the toughest exams- like Chinese and BC Calculus- have very high passing rates. Notice also the exams with very low 5 rates (below 10%), including Physics 1, English Literature, and Environmental Science. It will look especially impressive if you can earn a 5 on these tests! So Which AP Classes Should You Take? The goal of taking an AP class is to get a good grade in it and also pass the AP test. Doing both these things will show colleges that you can handle college-level material, and scoring high enough on the AP test can help you get college credit. You want to take AP classes you think you'll do well in. However, be careful about signing up for exams based on their average scores alone. As we saw above, some of the toughest exams (like Physics, AB and BC Calculus, and many of the foreign languages) have the highest passing rates, and some of the easiest exams (like Environmental Science and Human Geography) have the lowest passing rates. This means you shouldn't sign up for AP classes based on just their passing rates. Do some research before signing up for an AP class and make sure it’s the right fit for you. Ask older classmates how difficult they've found certain AP classes. Also, think about your own academic strengths and the classes you enjoy the most. If you love math and have always been good at it, you can probably score well on an AP Calculus exam even though they're known for being difficult. Also be careful not to overload yourself! If you cram too many AP classes into your schedule, it will be harder to pass the exams. Finally, note that these are the national averages. The passing rates for different subjects could be very different at your school. If you want to find out the passing rates for these classes at your school, talk to your guidance counselor and they can help you find that info. For example, some teachers have passing rates for their AP classes above 90%. If you have a teacher like that at your school, and they teach an AP subject you are interested in, you will likely have a very high chance of passing. One last word of advice: check out our scoring guide to see how AP scores are calculated to help you develop a target raw score to help you pass. Understanding how the exam is scored is a very important step in preparing for AP tests. What's Next? Learn about what AP Exams are like and how to avoid fatigue. Check out our guide on AP test length for exclusive tips! Want help deciding which AP classes will be easiest for you to take? We will show you which factors to consider to find the easiest AP classes for your schedule. Trying to decide between the ACT and SAT? Read our guide to decide which is best for you- and learn why it’s best to just focus on one test. Get tips on the SAT from our 1600 Full Scorer- you can also put the same techniques to use when studying for AP exams, especially the multiple choice sections! Get advice on writing SAT and ACT essays. If you’re going for perfection, you can even learn how to write a perfect SAT essay or a perfect ACT essay. Want to improve your SAT score by 160 points or your ACT score by 4 points?We've written a guide for each test about the top 5 strategies you must be using to have a shot at improving your score. Download it for free now: