Origin of the Universe Flashcards
Scientific method
1) Develop an idea to explain an observation
2) Test the idea with new observation or by making predictions
3) If new observations do not agree with the idea or its predictions, modify the idea or develop a new one
Science
Human search for natural explanation of what the universe is; how it is constructed and how it came to be
Scientific theories must be…
Testable and their conclusions must be falsifiable
Truth in science
On science, an baser stood that has been repeatedly confirmed and for all practical purposes is accepted as “true.” However, truth in science is never final and what is accepted today may be modified or even discarded tomorrow.
Hypothesis
A tentative statement about the natural world leading to deductions that can be tested
Can be used to build more complex inferences and explanations.
How can one become more certain about a hypothesis?
If the deductions are verified
How can one become less certain about a hypothesis?
If the deduction is incorrect.
Law
A descriptive generalization about how some aspect if the natural world behaves under states circumstances.
Theory
1) A well-substantiated explanation if some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.
2) Do not turn into facts through the accumulation of evidence
3) The end point of science; they explain facts.
4) the understanding that develops from extensive observation, experimentation, and creative reflection.
5) Incorporate large body of facts, laws, tested hypotheses, and logical inferences
Pythagoras ~580-500 BC
Spherical rotating earth with a fire at the center (heliocentric); magic numbers
Plato ~427-367 BC
Planets circling stationary Earth (geocentric).
Observing mars and its retrograde motion disproves this theory.
Eudoxus ~408-355 BC
Math model with 33 spheres within sphere motions; clever attempt to reproduce retrograde motion.
Aristotle ~384-322 BC
Working model with 55 spheres (here, the theory becomes overly complex and unwieldy).
Aristarchus ~280 BC
Heliocentric system; was correct but ignored due to its overly radical nature.
Ptolemy 140 AD
Brightness problems; geocentric theory where each planet moved in a small circle/epicycles around the sun, which in turn circled earth
Copernicus (1473-1543)
Sun centered theory with circular orbits
Kepler (1571-1630)
Elliptical orbits
Galileo 1564-1642
Using a telescope to observe the phases of Venus, confirms heliocentric theory. Denounced by the Catholic church’s inquisition in 1633 and forced to recant his ideas
Newton 1643-1726
Force of gravity; rational basis for planetary motion
Herschel 1738-1822
1) Confirms gravity is universal
2) Discovers Nebulae outside Milky Way
3) Estimating distance to stars
Parallax of a planet
Distance to a planet (ex: Mars) can be measured using parallax angle. Angle depends on separation of the observatories and the distance to the planet.
Parallax of nearby stars
By observing a star at 6 month intervals, the Earth’s orbit is now the separation of the observatories (ex: Alpha Centauri is 4 light years from Earth).
Using brightness to estimate distance
Identify star types in Milky Way where we know the distance; use absolute brightness of the same star type in other galaxies to estimate distance (Doppler effect applies to light as well as sound)
Supernova explosion
1) As a large star’s hydrogen runs out it begins to collapse, temperature goes up, and the star explodes.
2) ~10 seconds long
3) All elements heavier than iron formed in this way
Fate of the universe
The Big Bang could expand the universe forever or gravity could cause it to collapse back in on itself; it all depends on the universe’s mass
