Week 11: How we come to realize that the earth is not the center of the universe Flashcards
believed that everything was related to mathematics and that through mathematics everything could be predicted and measured in rhythmic patterns or cycles
Pythagoras
a Greek term meaning ’wanderer’
planet
also one of the first to think that the Earth was round, a theory that was finally proved around 330BCE by Aristotle.
pythagoras
Aristotle believed that the only eternal motion is circular with a constant speed, the motions of the planets must be circular.
The Principal of Uniform Circular Motion
a citizen of Egypt which was under Roman rule during Ptolemy’s lifetime. During his lifetime he was a mathematician, astronomer, and geographer. His theories dominated the world’s understanding of astronomy for over a thousand years
Claudius Ptolemy
as outlined in the Almagest, the Universe according to Ptolemy was based on five main points:
1) the celestial realm is spherical,
2) the celestial realm moves in a circle,
3) the earth is a sphere,
4) the celestial realm orbit is a circle centered on the earth,
5) earth does not move
some of the planets appeared to move in the opposite direction of their normal movement. This reverse direction movement is referred to as
retrograde motion
The Ptolemaic system had circles within circles that produced
epicycles
sun-centered design
heliocentric
the year Copernicus introduced a sun-centered design (heliocentric), that Ptolemy’s astronomy was seriously questioned and eventually overthrown.
1543
Kepler’s Laws of Planetary Motion
- The orbits of the planets are elliptical.
- An imaginary line connecting a planet and the sun sweeps out equal areas during equal time intervals.(Therefore, the earth’s orbital speed varies at different times of the year. The earth moves fastest in its orbit when closest to the sun and slowest when farthest away.) Kepler’s Second Law of Planetary Motion was calculated for Earth, then the hypothesis was tested using data for Mars, and it worked!
- Kepler’s Third Law of Planetary Motion showed the relationship between the size of a planet’s orbit radius, R(12the major axis), and its orbital period, T.R2=T3This law is true for all planets if you use astronomical units (that is, distance in multiples of earth’s orbital radium and time in multiples of earth years). Kepler’s three laws replaced the cumbersome epicycles to explain planetary motion with three mathematical laws that allowed the positions of the planets to be predicted with accuracies ten times better than Ptolemaic or Copernican models.
provided the crucial observations that proved the Copernican hypothesis, and also laid the foundations for a correct understanding of how objects moved on the surface of the earth and of gravity. One could, with considerable justification, view Galileo as the father both of modern astronomy and of modern physics
Galileo Galilei
the dominant and highly supported theory of the origin of the universe. It states that the universe began from an initial point which has expanded over billions of years to form the universe as we now know it
big bang theory
In 1922 ___ found that the solutions to Einstein’s general relativity equations resulted in an expanding universe. Einstein, at that time, believed in a static, eternal universe so he added a constant to his equations to eliminate the expansion. Einstein would later call this the biggest blunder of his life.
Alexander Friedman
In 1924, ___ was able to measure the distance to observed celestial objects that were thought to be nebula and discovered that they were so far away they were not actually part of the Milky Way (the galaxy containing our sun). He discovered that the Milky Way was only one of many galaxies.
Edwin Hubble
In 1927 ___ a physicist, suggested that the universe must be expanding. Lemaitre’s theory was supported by Hubble in 1929 when he found that the galaxies most distant from us also had the greatest red shift(were moving away from us with the greatest speed). The idea that the most distance galaxies were moving away from us at the greatest speed was exactly what was predicted by Lemaitre
Georges Lemaitre
What year did Lemaitre went further with his predictions and by extrapolating backwards, found that the matter of the universe would reach an infinite density and temperature at a finite time in the past (around 15 billion years)? This meant that the universe must have begun as a small, extremely dense point of matter.
in 1931
predicted that new matter was created which made it appear that the universe was expanding but that the universe was constant
steady state theory
who coined the term “Big Bang Theory” which he used as a derisive name for Lemaitre’s theory?
Hoyle
the major advocate of the Big Bang theory
George Gamow
predicted that the expansion of the universe would cool the original radiation so that now the radiation would be in the microwave range.
Gamow
The temporary apparent motion of a body in a direction opposite to that of the motion of most members of the solar system
retrograde motion
A construct of the geocentric model of the solar system which was necessary to explain observed retrograde motion. Each planet rides on a small epicycle whose center in turn rides on a larger circle
epicycles
The heliocentric model of astronomy is the theory that places the sun at the center of the solar system, with all the planets orbiting around it.
heliocentric
A theory that deduces a cataclysmic birth of the universe from the observed expansion of the universe, cosmic background radiation, abundance of the elements, and the laws of physics.
big bang theory
