Science thinking and every day thinking
Scientific thinking is based on everyday observations and trial-and-error experiences
Why ancient people observed sky?
To keep track of time and seasons and as aid of navigation
Options how ancient people keep track of time
1)»_space; determine the time of day: simplified clocks as sticks observing the Sun’s path during the daytime;
> > determine the time of night: observing the Moon’s position and constellations
Two-part day traces it origins from ancient Egyptians: they decided daytime and nighttime in 12 parts each =>
=> a.m (“ante meridiam”) and p.m. (“post meridiam”)
2) marking the seasons: building structures with cardinal directions (n, s, e, w) to keep track on the rise and set of the Sun over the course of the year (for example, Sun Dogger)
3) Solar and lunar calendars: we use solar calendar
> > > lunar calendar synchronizes with lunar phases, so on the first day of each month the moon is always the same
Why Greece?
Greece was located at a a crossroads of travelers, merchants, armies =>
=> diverse ideals from many cultures
3 (4) philosophical observation that we have borrowed from Greeks
1) tradition to explain by natural causes and not to rely on supernatural explanations
2) use Math to peruse explanations
3) the power of reasoning from observation
4) they made MODELS OF NATURE
Scientific model
Conceptual representation created to explain and predict observed phenomena
Geocentric model
A model of the universe developed by Greeks with Earth in the center of the celestial sphere
Ptolemaic model
A geocentric model each planet moves on a small circle which center in tern moves on a larger circle around Earth.
That explained apparent retrograde motion
Copernican revolution
Copernicus —> Tycho —> Kepler —> Galileo
Copernicus developed (more suggested) a Sun-centered model of the universe. But there was a problem with it — he still inherited Greeks idea of heavenly perfection with perfect circled orbits»_space;>
> > > Tycho then made accurate naked-eye observations that proved data needed to improve Copernicus System. But he still failed to detect stellar parallax so he didn’t come up with satisfying planetary motion theory. His final conclusion was that planets move around Sun, not Earth, but Earth itself is not moving»_space;>
> > > Kepler discovered that plants’ orbits are ellipses not circles == Kepler’s model ==» Kepler’s three laws of motion»_space;>
> > > Galileo defused main objectives against Copernicus assumption + “discover imperfection” in sky objects ==» Sun-centered universe concept
(»> Newton)
Kepler’s model
A Sun-centered model that implies elliptical orbits
(Accepted as a model of nature a truth about planetary motion)
Ellipse (components)
2 foci (sing, focus)
Major axis - the long axis of an ellipse
Minor axis - the short axis of an ellipse
Semi major axis = major axis/2 - average distance of an orbiting object (to the Sun) = (Perihelion-Sun distance + Aphelion-Sun distance)/2
Perihelion - a point at which an object orbiting the Sun is closest to the Sun
Aphelion - a point at which an object orbiting the Sun is farthest from the Sun
Eccentricity
A measure of how ellipse deviate from perfect circle
Circle eccentricity = 0 –> moderate eccentricity —> high eccentricity
More eccentricity, more elongated ellipse
Kepler’s first law
The orbit of each planet about the Sun is an ellipse with the Sun in one focus
Kepler’s second law
A planet moves faster when nearer to the Sun and slower when farther from the Sun, sweeping out the same Area
(»> Newton’s 2nd law)
Kepler’s third law
More distant planets orbit the Sun at slower average speed obeying the relationship p^2=a^3
Where p - orbital period — years
a - distance — in AU
Objections and Galileo’s defusing evidence of them
Objection 1: if Earth is moving why such objects as birds, falling stones, clouds would left behind
Galileo’s defusing evidence: an object remains in motion unless external force stops it => things don’t need a constant push => all objects are sharing the movement with Earth
Objection 2: heavenly perfection
Galileo’s defusing evidence: he spotted dark spots on the Sun and mountains and valleys on the Moon all of which were considered imperfections
Objection 3: ancient people weren’t able to observe stellar parallax
Galileo’s defusing evidence: he also couldn’t catch stellar parallax but he discovered that starts are more numerous and far more distant that it was believed by Tycho and before him
2 additional discoveries:
1 - he spotted 4 moons orbiting Jupiter, not Earth
2 - he observed that Venus goes through phases in a way that means must orbit the Sun, not Earth ==»
==» Earth is not the center of everything
Scientific method
Is in fact an idealization of scientific thinking
Its scheme: Make observation
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Ask a question
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————> Make a hypothesis
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| Make a prediction <———
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If doesn’t support, revise <—— Test ——> if supports make additional prediction(s)
Hypothesis or make a new one
Scientific theory
A simple yet powerful model that explains the wide variety of observations using just a few general principles, and that has survived repeated and varied testing
Hallmarks of science
~ explanations rely solely on natural causes
~ progress through creation and testing of models of nature that explain the observation as simple as possible
~ must take testable predictions which are if not supported reviewed or abandoned
Occam’s rezor
An idea that scientist should prefer the simpler of two models that agree equally well with observations
