What we’ve learned so

far…

Geocentric Model of the Universe

The Geocentric Model of the universe states…That everything revolves around the Earth, and to justify the path, Ptolemy included a bunch of loops.

The Heliocentric Model

• That everything revolves around the sun. Copernicus thought that the whole universe revolved around the sun. REALLY, everything in our solar system revolves around our sun.

• Galileo supported this idea.

Hypothesis

• A Hypothesis is… an educated guess. A “guesstamation”. Generally made before an experiment. And experiments are designed to test a hypothesis.

Theory…

• A Theory is… a tested hypothesis that is reliable in nature. Must be widely accepted and undisputed.

• What is an Empirical Theory? Comes from observations, involves a working hypothesis and must be testable/provable.

Law

• A Scientific Law is… universally accepted observations to explain phenomena, does not necessarily involve an experiment.

Copernicus

• What is Copernicus famous for? The Copernican Revolution. The world accepted the ideas involving a heliocentric model.

• Did he have it all right? No, he thought everything revolved around the sun, but really only the solar system does.

Kepler

• Came up with 3 laws starting in 1609… what are they?– 1st Law: Objects orbit in an ellipse, not a circle.– 2nd Law: SPEED… Objects sweep out equal areas in equal

times. This means that when they are closer to the sun they move faster, and when they are further away they move slower.

– 3rd Law: a3 = p2, where a is the semi-major axis, p is the orbital period. The further away it is, the slower it moves.

• The eccentricity of a perfect circle is? 0

Elliptical Orbits… label the major axis, minor axis, the semi-major axis, perihelion, aphelion, major focus and minor focus.

Edwin Hubble • Hubble Telescope named after him (put into

space in the 1990’s). Hubble was born 1889 and died in 1953). Developed the idea of an expanding universe. He came up with Hubble’s constant.

Edwin Hubble used the data created by Henrietta Leavitt to discover that galaxies were moving away from us, and therefore discovered that everything was expanding.

Henrietta Swan Leavitt

• Made discoveries about Cepheid variables, starts which change their brightness.

Newton’s Laws

• 1st Law: Law of Inertia. An object in motion stays in motion unless acted on by an outside force.

• 2nd Law: F=ma. • 3rd: Every force has an equal and

opposite force.

Galileo

• Rotation period of the sun: Using the observation of sunspots, the rotation of the sun can be monitored. The sun is not a solid mass and experiences “Differential Rotation” The equator of the sun rotates faster (~ 27 day rotation) while the poles rotate slower (~31 days to rotate). Supported the Copernican revolution. The Catholic church threatened to torture him and put him under house for the rest of his life.

Albert Einstein

• Created the theory of general relativity

Solstices and Equinoxes

• A solstice is when we experience the longest/shortest day of the year.

• Maximum tilt is facing the sun. Equinox is when the daytime and night-

• Times are equal. • The winter equinox in the southern

hemisphere is the (longest/shortest) day of the year.