Earth and Space Science

1. Earth and Space Science • Introduction: • TEK (2)  Nature of science. Students should know that the vast body of changing and increasing knowledge about the Earth in space, is described by physical, mathematical, and conceptual models. • TEK (5)  (A)  Earth has a long, complex, and dynamic history. Advances in technologies continue to further our understanding of the origin, evolution, and properties of Earth and planetary systems within a chronological framework. Essential Question: Why is an understanding of how the science of Astronomy “evolved” important to know about, when considering today’s knowledge about the universe?

2. Evolution of Astronomy • Students will be able to: • Describe Ptolemaic model of the universe • Discuss contributions made by Aristotle, Aristarchus, Galileo, and Hubble • Understand Copernicus’ contributions to the heliocentric solar system • Describe Kepler’s three laws of planetary motion and • Understand how Newton’s Laws helped Kepler develop his laws of planetary motion.

3. 384 BC-322BC Aristotle • In any discussion of scientific thought, Aristotle must come first. He was a Greek who studied under Plato. He… • knew that the Earth was a sphere, and • the light we see from the moon, is actually sunlight. • He is known as the father of science because of his many observations, both accurate and inaccurate. • He believed in a geocentric model (Earth-Centered) of the universe, had no knowledge of forces such as gravity or inertia, so Earth was static (unmoving). What observations did he make that led him to believe everything in the universe moved around the Earth?

4. Retrograde Motion To the ancient Greeks, the stars traveled daily around the Earth on a transparent, hollow sphere called the celestial sphere. It was Aristarchus (312-230 BC) who first proposed the heliocentric model, that placed the Sun in the middle of everything. This model was centuries ahead of its time, and so was Aristarchus! Aristarchus came to this conclusion after very cleverly observing something called “retrograde motion”. Planets exhibit an apparent westward drift. In this photo series of Mars’ retrograde motion, you can see how it appears to double back on itself. Here is an animation of Venus and the Earth that shows retrograde motion of that planet.

5. The Birth of Modern Astronomy Early Greeks believed that the Earth lay at the center of the universe. This is known as the “Geocentric” model. Geo=Earth Centric=Centered Notice, there were seven bodies orbiting the Earth in the Ptolemaic Model • The Sun • The Moon • Mercury • Venus • Mars • Jupiter • and Saturn All other bodies in space appeared to be stationary. While the idea of geocentrism was established in the time of Aristotle, the details of this model would not become a scientific standard until the time of Claudius Ptolemy (AD90-AD168). His geocentric model became known as the Ptolemaic Standard The area beyond the orbiting bodies was known as the firmament, or the area of space that was infinite with fixed stars, aka “heaven”.

6. Another name for an Earth-centered universe is______________ and the ____________ believed this because of improper observations. • In Ptolemy’s model of the universe, what was the firmament? • What model correctly placed the Sun at the center? • Who was the first to propose a helio-centric model? • Which model did Aristotle’s observations support?

7. 1500s-1600s • These years were known as the time of the birth of modern astronomy. The big 4 were: • Nicolaus Copernicus • Galileo Galilei • Johannes Kepler • Sir Isaac Newton I’m sure you’ve heard most of their names before, but here is a brief synopsis of what each one contributed to the field of space science…

8. Nicolaus Copernicus 1473-1543 • Copernicus was the first to • Conclude that Earth was a planet. • Prove Aristarchus’ thought that the Sun was at the center of things. • Usher in the new age of astronomy. Copernicus continued to believe…in error…that the planets traveled around the sun in circular paths. Of course, we know today, that the planets orbit the Sun in “elliptical” paths. The Earth’s path in this diagram is greatly exaggerated, however, it also shows how the Earth’s gravitational field could influence the Sun’s motion. When the Earth is closest to the Sun in its orbit (a point called Perihelion), as small as we are, we do influence the Sun slightly, pulling it towards us.

9. Copernican Contributions: Copernicus’ scientific findings that the Earth revolved around the Sun, and not the other way around, was hugely significant. This really upset the theologians of the day, who for millennia had believed that the Earth was the center of everything. Next to Darwin’s theory of Natural Selection, this concept did the most to disrupt our thoughts about the role of humans in the universe. It made us feel much smaller.

10. 6. What were Copernicus’ contributions to astronomy? • What were Copernicus’ misconceptions about astronomy? • What shape is the actual path of the planets around the Sun? • What name is given to the point in Earth’s orbit where it is closest to the Sun?

11. Galileo Galilei • Galileo • found evidence to support Copernican theory • Used experimental data • Constructed an astronomical telescope in 1609 • Found four large moons around Jupiter • Discovered features on the moon • Discovered sunspots 1564-1642 Galileo was one of the first to recognize sunspots as actual surface features on the sun, rather than intramercurial planets. (planets between mercury and the sun)

12. Johannes Kepler 1571-1630 • Kepler: • Proved that planets revolve around the Sun • Founded the three laws of planetary motion: • Orbits of the planets are elliptical • Planets revolve around the Sun at varying speeds • There is a proportional relationship between a planet’s orbital period and its distance to the Sun (as measured in AUs) If it takes the Earth the same amount of time to travel from A-B, as it does for it to travel from C-D, then it is obvious that the Earth will travel faster when it is closest to the Sun (at perihelion)

13. Kepler's third law of motion states the obvious. The relationship between the orbital period of a planet and its distance from the Sun is direct. This relationship is mathematical and can be summarized in the equation: Kepler’s Third Law P2 = d3 0r p2 = a3 In the equation, "p" stands for the orbital period of the planet measured in years and "a", for the average distance of the planet from the Sun measured in astronomical units. The significance of Kepler's third law is that given the period of revolution of any body, be it a planet or a moon, one can calculate the size of its orbit. If it takes a planet 8 years to revolve around our sun, what is the size of its orbit (how many AUs?) p2 = d3 or p2 = a3 So: 82 = a3 Or: 64 = a3 Or: a = 4 p2 =d3 or p2 = a3 So: p2 = 53 Or: p2 = 125 Or: p = 11.18 years You can also do this in reverse. If a planet has an orbital distance of 5 AUs, how long does it take the planet to revolve around the Sun?

14. Sir Isaac Newton 1643-1727 Sir Isaac Newton set forth: • The law of universal gravitation • that the force of gravity, combined with the tendency of a planet to remain in straight-line motion (inertia), resulted in the elliptical orbits discovered by Kepler.

15. Edwin Hubble1889-1953 In 1919, the prevailing view of the cosmos was that the universe consisted entirely of the Milky Way Galaxy. Using the Hooker Telescope at Mt. Wilson, Hubble identified Cepheid variables (a kind of star) in several spiral nebulae, including the Andromeda Nebula and Triangulum. His observations, made in 1922–1923, proved conclusively that these nebulae were much too distant to be part of the Milky Way and were, in fact, entire galaxies outside our own. Hubble also devised the most commonly used system for classifying galaxies. Long after his death, the launching of the Hubble Space Telescope (named in honor of Hubble) in 1990 on the Space Shuttle, remains in low-Earth orbit taking photos of astronomical observations. Hubble’s ultra deep field image reveals over 10,000 galaxies!

16. Hubble Through Hubble’s observations, he was able to also see the Universe expanding…and thereby came up with the “Big Bang” Theory of Universe Origins. Without giving anything away, this was probably Hubble’s largest contribution to Astronomy, as it is what science claims to this day.

17. 10. What were Galileo’s main contributions to astronomy? 11. What were Kepler’s contributions to the science of astronomy? 12. What are the 3 Laws of Planetary Motion? 13. Write and describe Kepler’s equation that summarizes his 3rd Law. 14. What were Isaac Newton’s contributions to astronomy? 15. How did Edwin Hubble contribute?

18. In your journals, construct a thinking map called a “Trace Map”. This is a combination of a Tree Map (used to classify and categorize), and a Brace Map, used to go from whole, to parts. This thinking map should list at least 2 contributions from EACH scientist. Remember… contributions, not misconceptions! Hubble Many galaxies Galaxy classification system Just how many scientists did we learn about between Aristotle and Hubble? Proved Big Bang When you’ve finished…color contributors in one color, and their contributions in another. Your choice! 6 Aristotle Moon reflects sunlight Earth was a sphere