The Enlightenment and Modern Astronomy

Galileo and the Telescope  Galileo did not invent the telescope but he was the first person to use a telescope to study the sky  He did make improvements in power © National Library of Medicine

Galileo and the Moon  Galileo made observations such as  The Sun’s surface has relatively dark spots  mountains and valleys on the Moon  many more stars than can be observed with the naked eye  These ideas were unsettling to those who believed in “perfection of the heavens” Chapter 1, Lesson 3

Galileo’s Observations of Jupiter  Four moons revolved around Jupiter  Io, Europa, Ganymede and Callisto never appear north or south of Jupiter  Suggested to Galileo that their orbital plane aligned with that of Earth  Contradicted the theory that Earth must be stationary or it would lose its Moon Chapter 1, Lesson 3

Venus has phases like those of Earth’s Moon Courtesy Lowell Observatory Galileo’s Observations of Venus

 Venus seems to change size  Arc of Venus’s crescent is much larger than the full Venus, showing that it is significantly closer to Earth at that time  Supports the Sun-centered model Chapter 1, Lesson 3 Galileo’s Observations of Venus

Newton’s Three Laws of Motion  Inertia - the tendency of an object to resist a change in its motion  Newton’s First Law of Motion: A body in motion tends to stay in motion, and a body at rest tends to stay at rest ©Photos.com

Newton’s Three Laws of Motion  Newton’s Second Law: How much force is necessary to produce a certain acceleration of an object  The acceleration of an object is proportional to the force exerted on it.  Force = mass x acceleration (F=ma) Chapter 1, Lesson 3

Newton’s Three Laws of Motion A)The wheeled brick will accelerate B) if a force is exerted on it. C)If twice as much force is exerted on it, it will accelerate at twice the rate. D) The same amount of force will give twice as much mass only half the acceleration. Newton’s Second Law

Newton’s Three Laws of Motion  Newton’s Third Law of Motion: For every action there is an equal and opposite reaction  Forces always occur in pairs. It is impossible to have a single, isolated force.  You can call one force the action force and the other the reaction force. Chapter 1, Lesson 3

The Basic Law of Gravity  Every object in the universe attracts every other one  The greater the mass of an object, the greater the attractive force it exerts on other objects  The greater the distance the less attractive force  On Earth the force of gravity made objects fall to the ground  Gravity also held the Moon in orbit around the Earth, and the planets in their orbits around the Sun Chapter 1, Lesson 3

How Newton’s Laws Confirmed Kepler’s  Sun was the largest object in the universe and therefore the source of the force responsible for the motion of the planets  The gravitational force acting on an object orbiting the Sun (or other stationary body) always points toward the Sun  Laws of motion and gravity can be applied to any two objects orbiting each other Chapter 1, Lesson 3

Einstein and Relativity  Principle of Equivalence – effects of acceleration are indistinguishable from gravitational effects © AIP Emilio Segrè Visual Archives

 No place in the universe is stationary or “at rest”  Everything is in motion relative to everything else.  The rules of nature are the same everywhere in the universe.  Light always travels at the same speed regardless of the observer’s speed Chapter 1, Lesson 3 Einstein and Relativity

Einstein and Space Curvature  Einstein proposed thinking of space as being curved by a mass – objects move because of the curvature  Three dimensions are needed to describe the position of something  North-South  East-West  Up-Down  Picture the space near the Sun as being warped as the surface of a waterbed is warped by a bowling ball placed at its center. Chapter 1, Lesson 3

Bending of Light Proves Einstein Theory of Space Curvature  It takes a very massive object to bend light with gravity in an amount you can detect  During the 1919 eclipse, light from two stars bends and makes the stars appear farther apart

Review  Galileo used the telescope to make observations that informed the debate between heliocentric and geocentric theories  Sir Isaac Newton was the first to create a unified model of how the universe works  Scientists’ much greater understanding of the universe would not have been possible without Einstein Chapter 1, Lesson 3

Summary  Galileo and the Telescope  Newton’s Laws of Motion and Gravity  Einstein and Relativity Chapter 1, Lesson 3

Next…  Done - Enlightenment and Modern Astronomy  Next - Earth: Inside and Out Courtesy of NASA