Chapter 26.2: Observing the Solar System

1
Chapter 26.2 Observing the Solar System
2
Early views of the organization of Space were
much different than ours.
3
Early astronomers believed that the Earth was the
center of our Universe, and that the Earth was
surrounded by a ball, called a Celestial Sphere,
on which were fixed most of the objects of the
heavens.
4
This interpretation of our solar system is called
a Geocentric Model, meaning Earth-centered.
5
Early astronomers noticed groups of stars that
were visible at the same time every year. These
were named constellations, and were used as a
basis for calendars.
The Orion Constellation
6
Astronomers noticed that some celestial bodies
did change position relative to the
constellations. They called these wandering
stars planets.
Notice the planet Mars moving across the
constellations Gemini and Leo over the course of
11 months.
7
Astronomers also noted that, periodically, these
planets which normally moved eastward, moved
backward for a few weeks, then resumed their path
eastward. This is referred to as retrograde
motion.
8
(No Transcript)
9
In 200 A.D., the Greek astronomer Ptolemy
explained this retrograde motion by stating
that the planets orbited the Earth in a circle,
but also orbited another point in a circle, what
he called an epicycle.
10
(No Transcript)
11
In the late 1400s, the astronomer Copernicus
proposed what was to become known as the
Heliocentric Model.
12
Copernicus stated that the Sun was the center of
the Solar System, the Earth was a planet, and
that it orbited the Sun.
13
And, here is how he explained retrograde motion.
14
Mars retrograde motion
Venus retrograde motion
15
In the 16th century, the astronomer Johannes
Kepler developed three laws to describe the way
in which planets move through Space.
16
Keplers 1st Law Planets move through Space in
an elliptical orbit, not a circular one. This
causes the distance from a planet to the Sun to
vary.
17
Keplers 2nd Law When a planet is closer to the
Sun, it moves faster. (centrifugal force and
gravity at work!)
18
Keplers 3rd Law states that the further a planet
is from the Sun the longer its period of
revolution (its year) will be.
19
In the 1600s, Isaac Newton stated that a force
called gravity was causing the planets to behave
as Kepler had observed.
20
He stated that all objects with mass exerted a
force of attraction on other objects with mass,
and that the strength of that force is
proportional to the mass of the objects and their
distances from one another.
21
Astronomers
Early Astronomers
22
Ptolemy
devised the geocentric model for our solar system believed until 1500's said planets are on small circular orbits, called epicycles developed 1st model to predict the positions of planets had support of Catholic church, despite inaccuracy
AD 90-168
23
challenged Ptolemy's geocentric model and proposed the heliocentric model for our solar system suggested the Earth was a planet, it rotated, and that Earth other planets revolved around the sun tried to explain retrograde motion (i.e. when 2 bodies move the same direction one moves faster than the other
Copernicus
1473-1543
24
discovered that planets orbit in ellipses, not circles developed 3 laws of planetary motion "planets travel in elliptical orbits with the sun at one focus the planet's distance from the sun varying" equal area law "the speed at which the planet travels around the sun is not constant planets closer to the sun orbit faster than those further away" harmonic law "the period of a planet squared is equal to the mean distance cubed P squared D cubed
Johannes Kepler
1571-1630
25
Galileo Galilei
explained why we don't feel the Earth moving first to use a telescope invented refracting telescope discovered Jupiter's 4 largest moons and proved that they revolved around Jupiter disproving geocentric model
1564-1642
26
Isaac Newton
incorporated a mirror into Galileo's telescope(refracating telescope), doubling its power (reflecting telescope) said that gravity keeps the planets in orbit- supported by his 3 laws of motion Newton's 3 laws of motion an object at rest stays at rest until another force acts on it the greater the mass of an object being accelerated, the more force needed to accelerate the object for every action, there is an equal but opposite reaction
1642-1727
27
Joseph Von Fraunhofen
invented the spectroscope invented many telescopes and optical instruments to describe stellar parallax Analyzed light (spectroscopy) to determine chemical composition of stars
1787-1826
28
Theory of Relativity adds the effect of gravity of large masses to light and time (predicts black holes) corrected Newton's theory of gravity by saying that not all objects attract all other objects E mc2
Albert Einstein 1879-1955
29
Hubble's Law all objects in deep space possess Dopplar shift and this shift is proportional to their distance from Earth. demonstrated the existence of other galaxies than our own with Dopplar shift, he proved that our universe is expanding and continuously moving away from us disccovered and analyzed "cosmic background radiation" which supports Big Bang Theory
Hubble Telescope In orbit since April 24, 1990
Edwin Hubble
1889-1953