Astronomy September 12-14

apparent daily motion of the sun, moon, stars etc

The earth rotates 360 degrees in one day, so celestial objects appear to move across the sky at 15 degrees an hour

Extending your arm, your fist is 10 degrees

The center of the sun is geometrically 12 degrees below the horizon, so the horizon is still visible and allows reliable navigational star sightings

Center of sun is geometrically 6 degrees blow the horizon, artificial illumination isn’t required outdoors

Center of sun is geometrically 18 degrees below the horizon, light from sun is less than starlight

Yearly motion, the complete motion around the sun

Earth has a rotational axial tilt of 23.5 degrees, which causes ____

The rising and setting points of the sun

A solar system with Earth in the center, equinoxes/eclipses/solstices were off by days to months

Proposed the heliocentric solar system and explained retrograde motion as an optical illusion

Best known for using his telescopic observations and supporting the copernican system, wrote Sidereus Nuncius and discovered Sun’s spots, Jupiter’s moons

Didn’t accept the Copernican model, believed in teh Tychonic system, built a planetarium to prove his theory correct and made incredibly accurate measurements of Mars

Discovered the three laws of planetary motion

The orbits of the planets are ellipses with the sun as one focus, eccentricity describes the shapes of the planet’s orbits

Law of areas, a line from the sun to a planet sweeps out an equal area in an equal amount of time, planets move faster the closer it is to the sun

Harmonic law, the square of the planet’s orbital period is proportional to the cube of its mean distance from the sun. If you know a planet’s distance from the sun, you can determine it’s orbital period

Invented physics, the laws of motion, the law of universal gravitation and explained orbits

Law of inertia, a body in motion will remain in motion unless acted upon by an outside force, and will remain at rest until acted upon

In order to accelerate a mass you must apply a force, usually expressed as an algebraic equation f=ma

For every action there is an equal and opposite reaction

Gravity works between pairs of objects, between any two objects in the universe there is a mutual attraction that is proportional to the product of their masses and inversely proportional to the square of the distance of separation between their centers

An object is actually in a constant state of falling, tangential velocity and acceleration combine to create this