Volcanoes and Igneous Activity Earth Chapter 4

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Chapter 22
The Origin of Modern Astronomy
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Chapter 22.1 Part 2

• From Early Astronomy to the Birth of Modern
  Astronomy!

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The Birth of Modern Astronomy
? Modern Astronomy

• In the mid to late 1400s scientists began to
  break from the philosophical and religious views
  that had governed astronomy for almost 13
  centuries after the time of Ptolemy.
• Scientists began to discover a universe governed
  by natural laws.
• The first of these great astronomers was Nicolaus
  Copernicus.

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The Birth of Modern Astronomy
? Nicolaus Copernicus 1473 - 1543

• Copernicus was a Polish astronomer that emerged
  after the Middle Ages.
• He felt that the Earth was a planet, just like
  the five other planets known at that time.
• He also reasoned that the daily motions of the
  heavens could be better explained by a rotating,
  rather than immobile, Earth.

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The Birth of Modern Astronomy
? Copernican Model

• Nicolaus Copernicus proposed a model of the solar
  system with the sun at the center and the planets
  Mercury, Venus, Earth, Mars, Jupiter, and Saturn
  orbiting around it which is also known as the
  heliocentric or sun-centered universe.

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The Birth of Modern Astronomy
? Nicolaus Copernicus 1473 - 1543

• Copernicus also used circles in his model, which
  were considered to be the perfect geometric form,
  to represent the orbits of the planets in his
  model.

• Unfortunately, these circles didnt match the
  motion of the planets that people observed in the
  night sky.

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The Birth of Modern Astronomy
? Tycho Brahe 1546 - 1601

• Tycho Brahe was a Danish nobleman and is best
  known as the greatest pre-telescopic observer.
• A child prodigy that attended a university at the
  age of 13, he persuaded King Frederick II to
  build an observatory for him.

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The Birth of Modern Astronomy
? Tycho Brahe 1546 - 1601

• Tycho designed and built instruments to
  measure the locations of the heavenly bodies.
• His careful observations, especially of the
  planet Mars, were far more precise than any other
  before him.
• In the last year of his life, Tycho found a very
  talented assistant, Johannes Kepler

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The Birth of Modern Astronomy
? Johannes Kepler 1571 - 1630

• Johannes Kepler used the careful observations of
  Tycho Brahe to determine that Mars did not
  revolve around the sun in a perfect circle.
• Instead, he determined that the planets
  revolved around the sun in an oval-shaped path
  called an ellipse.
• He also realized that Mars revolved around the
  sun at varying speeds.

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The Birth of Modern Astronomy
?Keplers Laws

• Kepler created the three laws of planetary motion

1. Orbits of the planets are elliptical with the
sun at one focus.
2. Planets revolve around the sun at varying
speed. It travels more rapidly when it is closer
to the sun and slower when it is further from the
sun.
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The Birth of Modern Astronomy
? Keplers Laws

• 3. There is a proportional relationship between a
  planets orbital period and its distance to the
  sun.
• Orbital period is measured in Earth years and a
  planets distance to the sun is measured in AUs.
• An astronomical unit (AU) is the average
  distance between Earth and the sun which is
  around 150,000,000 km.

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The Birth of Modern Astronomy
? Galileo Galilei 1564 - 1642

• Galileo was the greatest Italian scientist of the
  Renaissance.

• In 1609, Galileo heard that a Dutch lens maker
  had invented an object which used lenses to
  magnify objects.
• Galileo created his own version of this telescope
  and used it to observe the night sky.

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The Birth of Modern Astronomy
? Galileo Galilei 1564 - 1642
Galileos most important contributions were
his descriptions of the behavior of moving
objects, which supported the Copernican or
sun-centered view of the universe.
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The Birth of Modern Astronomy
? Galileos Observations

• Four satellites, or moons, orbit Jupiter.
• Today we know these objects to be the four
  largest moons of Jupiter, which has a total of
  16 satellites orbiting it, and they are named
  the Galilean satellites him!

Galileos Drawing of the Jupiters 4 largest
moons.
Pictures of the actual Galilean Satellites taken
by the Voyager Spacecraft.
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The Birth of Modern Astronomy
? Galileos Observations
2. Planets are circular disks, not just points of
light.
3. Venus has phases just like the moon.
4. The moons surface is not smooth.
5. The sun has sunspots, or dark regions.
Galileos Sunspot Drawings
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The Solar System Model Evolves
Picture A In the Ptolemaic system, the orbit of
Venus lies between the sun and the Earth.
A
C
Picture B In the Copernican system, Venus orbits
the sun and all its phases are visible from Earth.
B
Picture C The phases of Venus were first observed
by Galileo and they directly support the
Copernican system.
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The Birth of Modern Astronomy
? Sir Isaac Newton 1642 - 1727

• Sir Isaac Newton was one of the greatest
  mathematician and scientists that ever lived.
• He was born in England in 1643, the same year
  that Galileo died.
• At the age of 23, Newton described a force that
  extends from the Earths surface into space,
  holding the moon in orbit around the Earth.

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Gravitys Influence on Orbits
? Universal Gravitation

• Many scientists had attempted to explain the
  forces involved in planetary motion.
• Kepler believed some force pushed the planets
  along in their orbits.
• Galileo correctly reasoned that no force is
  needed to keep an object in motion. He also
  theorized that moving objects would continue in a
  straight line at a constant speed unless acted
  upon by an outside force, which is called
  inertia.
• Although others had theorized the existence of
  gravitational force, it was Newton that became
  the first to formulate and test the law of
  universal gravitation.

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Gravitys Influence on Orbits
? Universal Gravitation

• According to Newton, every body in the universe
  attracts every other body with a force that is
  directly proportional to their masses and
  inversely proportional to the square of the
  distance between them.

Newton discovered that visible light can be split
into the colors of the rainbow using a prism and
also invented a improved version of the telescope
called the Newtonian Telescope.
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Gravitys Influence on Orbits
? Universal Gravitation
Gravitational force decreases with distance.

• The greater the mass of an object, the greater
  is its gravitational force.
• We often confused the concepts of mass and
  weight.
• Weight is the force of gravity acting upon an
  object.
• Weight also varies when gravitational forces
  change.
• An example of this is the weight of an astronaut
  on the moon verses the weight of an astronaut on
  the Earth.

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Gravitys Influence on Orbits
? Universal Gravitation
An object weighs less on the moon than on the
Earth because the moon is on 1/6th the mass of
the Earth.
Astronaut on the Earth Mass 88.0kg Weight
863N
Astronaut on the Earth Mass 88.0kg Weight
141N
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Gravitys Influence on Orbits
? Universal Gravitation